View Article Online
Organic & Biomolecular Chemistry
View Journal
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Zhang, Y. Shao, Y. Wang, H. Li, D. Xu and X. wan, Org. Biomol. Chem., 2015, DOI: 10.1039/C5OB00109A.
This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
www.rsc.org/obc
View Article Online
Organic & Biomolecular Chemistry
DOI: 10.1039/C5OB00109A
Journal Name
RSCPublishing
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
ARTICLE
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012, Accepted 00th January 2012 DOI: 10.1039/x0xx00000x www.rsc.org/
Transition-metal-free decarboxylation of dimethyl malonate: an efficient construction of α-amino acid esters using TBAI/TBHP Jie Zhang, a Ying Shao,*b Yaxiong Wang, a Huihuang Li, a Dongmei Xu,*a and Xiaobing Wan*a A transition-metal-free decarboxylation coupling process for the preparation of α-amino acid esters, which succeeded in merging hydrolysis/decarboxylation/nucleophilic substitution, is well described. This strategy uses commercially available inexpensive starting materials, catalysts and oxidants and has a wide substrate scope and operational simp licity.
Introduction
Table 1 Optimization of reaction conditionsa O H N
The decarboxylative functionalizations have been developed as a powerful strategy to construct new molecular skeletons. 1 During the course of the past decade, the impressive field has attracted considerable attention and been studied systematically by a variety of groups, such as those of Gooßen,2 Myers,3 Tunge,4 and others,5 thus providing many new opportunities for the convenient construction of carbon–carbon or carbon–heteroatom bonds. Related to conventional carboxylic acids as coupling reagents, ester was also an ideal alternative because of its availability, solubility and neutrality. Since the pioneering work from the groups of Tsuji 6a and Saegusa6b in the beginning of the 1980s, the palladium-catalyzed decarboxylative allylic alkylation reaction of allylic ester has been extensively applied to construct C‒C in organic synthesis. 1b,4,6 However, other common esters were rarely employed as substrates in decarboxylative reaction. 7
O
O
MeO 1a
OMe
Catalyst, Oxidant OMe
N
90 oC, 12 h
3a
2a
Entry
Catalyst
Oxidant
Yieldb (%)
1
TBAI
TBHP
2
TBAI
H2O2
3
TBAI
Oxone
4
TBAI
O2
N.D.
5
TBAI
DTBP
N.D.
6
n-Bu4NCl
TBHP
N.D.
7
n-Bu4NBr
TBHP
N.D.
8
KI
TBHP
9
TBAI
10
86 34 N.D.c
69 N.D.
TBHP
N.D.
a
Scheme 1 Our design to construct α-amino acid esters. α-Amino acids and their derivatives are of great importance in the areas of chemical, biochemical, and material science and great endeavors have been devoted to the synthesis of these compounds.8 The nucleophilic substitution of amines to αhalogenated esters constitutes the conventional approach to this ubiquitous molecules. 9 Unfortunately, this method suffered from the generation of stoichiometric halide waste. Recently, we reported a new process for the preparation of α-amino acid esters from amines and monomethyl malonate using Bu 4NI as the catalyst and tBuOOH as the oxidant, 10 including sequential iodination, decarboxylation, and nucleophilic substitution reactions.11 Combining hydrolysis reactions of dimethyl malonate and subsequent decarboxylation, we herein envision a transition-metal-free entry to α-amino acid esters under mild conditions (Scheme 1).
Results and discussion
This journal is © The Royal Society of Chemistry 2013
0.5 mmol 1a, 7.5 mmol of dimethyl malonate 2a, 20 mol% catalyst, 2.9 equiv oxidant in 1.0 mL MeCN and 1.0 mL H 2O at 90 oC for 12 h. b Isolated yield. c Not detected. We started our investigations by examining the oxidative decarboxylation coupling reaction between N-methylaniline 1a and dimethyl malonate 2a for this C‒N formation reaction. Following extensive screenings, we found that the combination of Bu 4NI (20 mol%) and tBuOOH (2.9 equiv, 70% aqueous solution) in H2O/MeCN at 90 °C for 12 h afforded the desired product 3a in the best yield of up to 86% (Table 1, entry 1). In the case of 30% aqueous H2O2 chosen as the oxidant, the yield of 3a dropped from 86% to 34% (Table 1, entry 2). Other oxidants such as oxone, molecular oxygen, and di-tert-butyl peroxide (DTBP) were also examined and the reaction did not proceed smoothly (Table 1, entries 3-5). Replacing Bu4NI with either Bu4NCl or Bu4NBr halted the formation of compound 3a (Table 1, entries 6-7). Further investigations indicated that both Bu4NI and tBuOOH are crucial to the efficient conversion and the reaction could not work in the absence of Bu4NI or tBuOOH (Table 1, entries 9-10). In addition, a
J. Name ., 2013, 00, 1 -3 | 1
Organic & Biomolecular Chemistry Accepted Manuscript
Page 1 of 7
Organic & Biomolecular Chemistry
View Article Online
Journal Name
comparable yield was obtained when KI was used as the catalyst (Table 1, entry 8). Interestingly, compared to our previous work,11 base was unnecessary for the present transformation. Table 2 Scope of secondary aminesa H N
O +
OMe
MeO
1
R1
OMe
H2O/MeCN, 90 C 3
F
N
O
Cl N
N
MeO
O
OMe
N
O
OMe
3b, yield: 81%
Cl
N
O OMe
3d, yield: 72%
N
O
OMe
3e, yield: 84%
O
NC
N
O
OMe
OMe 3g, yield: 84%
3f, yield:77%
N
OMe
3c, yield: 53%
O
O
N
R2
o
2a
OMe
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
20 mol % TBAI
O
2.9 equiv TBHP R2
OMe
3h, yield: 65%
3i, yield: trace
N
N
Ph N
O
N
O
OMe
3k, yield: 41%
3l, yield: 80%
N
N
Table 4 Scope of tertiary aromatic aminesa
O
OMe
OMe
3j, yield: 81%
N
O
with ortho, meta or para substitutents on the aromatic ring could be converted to corresponding amino acid esters in moderate to good yields. Other N-alkyl substituted aromatic amines were also found to be the effective reaction partners (products 3k-3q). A variety of functional groups, such as alkoxyl (products 3b and 3e), alkyl (products 3f, 3h and 3j), halide (products 3c, 3d and 3g), benzyl (product 3k), and allyl (product 3p) group were tolerated under the optimized conditions. It is noteworthy that aromatic amines bearing electron-donating groups were found to give better results than those with electron-withdrawing groups, presumably owing to the better nucleophilicity. As a result, only trace amount of product 3i was detected when 4-(methylamino)benzonitrile was subjected to this reaction. To our delight, two secondary aliphatic amines were also suitable reaction partners for this transformation and the corresponding products 3r and 3s were furnished in moderate yields under slightly modified conditions. To further explore the potential of the methodology, some selected primary aromatic amines had also been employed as substrates, and moderate results could be achieved when switching the solvent to H2O/EA system (Table 3, 5a-5e).
OMe 3m, yield: 82%
N
O
O
O
OMe O
OMe
OMe
OMe
3n, yield: 71%
3p, yield: 41%
3o, yield: 77%
OMe
N N
OMe
N N
O
3q, yield: 62%
O
N 3r, yield: 47%b
3s, yield: 47%b
a
All the reactions were carried out in 1.0 mL of MeCN and 1.0 mL of H2O, using 0.5 mmol of 1, 7.5 mmol of dimethyl malonate 2a, 20 mol% of TBAI and 2.9 equiv of TBHP at 90 o C for 12 h. b 0.5 mL of t BuOH and 1.5 mL of H 2O were used as solvent at 80 oC. Table 3 Scope of primary aromatic aminesa O
R1
20 mol % TBAI
O
2.9 equiv TBHP
R1 NH2
+
MeO
H2O/EA, 80 oC
4
OMe 5
2a
O
H N
O
HN
OMe
H N
O
H N
OMe
OMe
O OMe
Cl 5a, R = H, yield: 45%
H N
O
5b, R = Me, yield: 41%
H N
5c, R = Cl, yield: 60%
O
OMe
OMe
OMe
Br
5d, yield: 47%
5e, yield: 64%
a
All the reactions were carried out in 1.0 mL of ethyl acetate (EA) and 1.0 mL of H 2O, using 0.5 mmol of 4, 7.5 mmol of dimethyl malonate 2a, 20 mol% of TBAI and 2.9 equiv of TBHP at 80 oC for 12 h.
a
All the reactions were carried out in 2.0mL of H 2O, using 7.5 mmol of dimethyl malonate 2a, 0.5 mmol of 6, 20 mol% of TBAI and 4.4 equiv of TBHP at 90 oC for 12 h. In 1988, Murahashi and co-workers reported the pioneering work of the transition-metal catalyzed N-dealkylation of tertiary amines under oxidative conditions. 12a However, further transformation via dealkylation of tertiary amines was sparsely reported. Li et al. recently demonstrated an iron catalyzed amide formation by oxidative amidation between tertiary amine and aldehyde. 12b Continuing our study, 11d we envisaged that the tertiary amines could undergo a dealkylation process to generate the secondary amines in situ, which subsequently reacts with dimethyl malonate 2a to afford the desired product. Then, N, N-dimethylaniline 6a was chosen as the source of secondary amines, and to our delight, 3a could be isolated. When the amounts of tBuOOH was incresaed to 4.4 equiv and H2O was used as the only solvent, a 55% yield was obtained (Table 4, product 3a). The similar results could also be achieved using other substituted N, N-dimethylanilines (Table 4).
With the optimized conditions identified, a series of amines were applied to this methodology as shown in Table 2. N-Methylanilines
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012
Organic & Biomolecular Chemistry Accepted Manuscript
ARTICLE
R1
Page 2 of 7
DOI: 10.1039/C5OB00109A
Organic & Biomolecular Chemistry
View Article Online
DOI: 10.1039/C5OB00109A
Journal Name
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
When diethyl malonate 2b was used as the reaction partner, the corresponding product 8 was given in lower yield compared with dimethyl malonate 2a, presumably owing to the relative stability of diethyl malonate in hydrolysis (eq 1).
ARTICLE In summary, we have developed a transition-metal-free process for the synthesis of α-amino acid esters through a tandem Bu4NI-catalyzed hydrolysis/decarboxylation/nucleophlic substitution. The advantages of this protocol include a wide range of substrates, high practical convenience, and commercially available materials. Compared to our previous report, base was not necessary at all. Notably, the more accessible and more stable dimethyl malonate, instead of monomethyl malonate, were used as substrate and tertiary amines were also adaptable substrates for this protocol via a C‒ N cleavage under mild conditions. Generally, we believe that this method provides a promising complementary access to previous methodologies.
Experimental
Scheme 2 Proposed catalytic cycle.
All manipulations were carried out under air atmosphere. Column chromatography was generally performed on silica gel (300-400 mesh) and reactions were monitored by thin layer chromatography (TLC) using UV light to visualize the course of the reactions. The 1H (300MHz or 400MHz) and 13C NMR (75MHz or 100MHz) data were recorded using CDCl 3 as solvent. The chemical shifts (δ) are reported in ppm and coupling constants (J) in Hz. 1H NMR spectra was recorded with tetramethylsilane (δ= 0.00 ppm) as internal reference; 13 C NMR spectra was recorded with CDCl 3 (δ = 77.00 ppm) as internal reference. General procedure for amines 1a-1q as substrates
Scheme 3 Investigations on mechanism. Next, a plausible mechanism was proposed for the transformation as depicted in Scheme 2. Initially, I - was oxidized to hypoiodite A in the presence of TBHP, 11,10d,10g-h, 10n followed by the iodination of 3-methoxy-3-oxopropanoic acid B generated in situ from the hydrolysis of dimethyl malonate to give the intermediate C. Then, the intermediate C could form iodoacetate D via decarboxylation. Finally, the desired α-amino acids ester was delivered through the classic nucleophilic substitution of amine to D with the release of I-. Some mechanistic experiments were conducted to better understand this α-amino acid esters formation reaction (Scheme 3). The use of 2.2 equiv I2 and 4 equiv Bu4NOH10d,10g,10h,10n resulted in the desired product 3a in 54% yield (Scheme 3a), which suggested that hypoiodite generated in situ might be the key catalytic species. To find out whether the hydrolysis of dimethyl malonate played an important role in this reaction, we removed the water from the model reaction using anhydrous TBHP (5-6 M in decane) and MeCN as sole solvent (Scheme 3b). As expected, the desired product 3a could not be detected. Notably, when compound 9 was subjected to the standard conditions, no desired product 3a was isolated, thus excluding the possibility of 9 as reaction intermediate (Scheme 3c).
Conclusions
This journal is © The Royal Society of Chemistry 2012
Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (1.45 mmol), 1.0 mL of MeCN and 1.0 mL of H2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 90 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product. General procedures for amines 1r-1s as substrates Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (1.45 mmol), 0.5 mL of tBuOH and 1.5 mL of H2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 80 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product. General procedures for amines 4a-4e as substrates Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (1.45 mmol), 1.0 mL of ethyl acetate (EA) and 1.0 mL of H 2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 80 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product.
J. Name ., 2012, 00, 1 -3 | 3
Organic & Biomolecular Chemistry Accepted Manuscript
Page 3 of 7
Organic & Biomolecular Chemistry
General procedures for tertiary amines as substrates
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (2.2 mmol), 2.0 mL of H 2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 90 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product. Methyl N-methyl-N-phenylglycinate (3a). 11 Colorless liquid (77 mg, 86% yield for amine 1a; 49 mg, 55% yield for amine 6a); 1H NMR (300 MHz, CDCl 3): δ 7.24 - 7.19 (m, 2H), 6.76 6.65 (m, 3H), 4.04 (s, 2H), 3.68 (s, 3H), 3.03 (s, 3H); MS (ESI): Anal. Calcd. For C10H14NO2: 180, Found: 180(M+H+); The data was in accordance with our previous report. Methyl N-(2-methoxyphenyl)-N-methylglycinate (3b). 11 Colorless liquid (85 mg, 81% yield); 1H NMR (400 MHz, CDCl3): δ 7.02 - 7.00 (m, 1H), 6.96 - 6.88 (m, 2H), 6.83 - 6.81 (m, 1H), 4.00 (s, 2H), 3.82 (s, 3H), 3.66 (s, 3H), 2.96 (s, 3H); MS (ESI): Anal. Calcd. For C11H16NO3 (M+H+): 210, Found: 210; The data was in accordance with our previous report. Methyl N-(2-fluorophenyl)-N-methylglycinate (3c). 11 1 Colorless liquid (52 mg, 53% yield); H NMR (400 MHz, CDCl3): δ 7.04 - 6.91 (m, 3H), 6.85 - 6.79 (m, 1H), 4.02 (s, 2H), 3.67 (s, 3H), 2.98 (s, 3H); MS (ESI): Anal. Calcd. For C10H13FNO2 (M+H+): 198, Found: 198; The data was in accordance with our previous report. Methyl N-(3-chlorophenyl)-N-methylglycinate (3d). 11 Colorless liquid (77 mg, 72% yield for amine 1d; 57 mg, 53% yield for amine 6c); 1H NMR (400 MHz, CDCl 3): δ 7.13 - 7.09 (m, 1H), 6.71 - 6.64 (m, 2H), 6.53 - 6.50 (m, 1H), 4.03 (s, 2H), 3.71 (s, 3H), 3.02 (s, 3H); MS (ESI): Anal. Calcd. For C10H13 35ClNO2 (M+H+): 214, Found: 214; For C10H13 37ClNO2 (M+H+): 216, Found: 216; The data was in accordance with our previous report. Methyl N-(3-methoxyphenyl)-N-methylglycinate (3e). Colorless liquid (88 mg, 84% yield); 1H NMR (400 MHz, CDCl3): δ 7.14 - 7.10 (m, 1H), 6.32 - 6.22 (m, 3H), 4.03 (s, 2H), 3.76 (s, 3H), 3.69 (s, 3H), 3.03 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 171.3, 160.6, 150.1, 129.8, 105.2, 102.0, 98.9, 54.9, 54.2, 51.7, 39.4; MS (ESI): Anal. Calcd. For C 11H16NO3: 210, Found: 210 (M+H+); IR (KBr, cm-1): υ 1750, 1613, 1502, 1201. Methyl N-methyl-N-(m-tolyl)glycinate (3f). Colorless liquid (74 mg, 77% yield for amine 1f, 50 mg, 52% yield for amine 6c); 1H NMR (400 MHz, CDCl 3): δ 7.13 - 7.09 (m, 1H), 6.58 6.56 (m, 1H), 6.50 - 6.47 (m, 2H), 4.04 (s, 2H), 3.70 (s, 3H), 3.03 (s, 3H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl 3): δ 171.5, 148.8, 138.8, 129.0, 118.3, 113.0, 109.4, 54.3, 51.8, 39.4, 21.8; MS (ESI): Anal. Calcd. For C 11H16NO2: 194, Found: 194 (M+H+); IR (KBr, cm-1): υ 1750, 1605, 1499, 1202. Methyl N-(4-chlorophenyl)-N-methylglycinate (3g). 11 1 Colorless liquid (90 mg, 84% yield); H NMR (300 MHz, CDCl3): δ 7.17 - 7.14 (m, 2H), 6.60 - 6.57 (m, 2H), 4.03 (s, 2H), 3.70 (s, 3H), 3.02 (s, 3H); MS (ESI): Anal. Calcd. For C10H13 35ClNO2 (M+H+): 214, Found: 214; For C10H13 37ClNO2 (M+H+): 216, Found: 216; The data was in accordance with our previous report. Methyl N-methyl-N-(p-tolyl)glycinate (3h). Colorless liquid (63 mg, 65% yield); 1H NMR (300 MHz, CDCl 3): δ 7.04 - 7.01 (m, 2H), 6.62 - 6.59 (m, 2H), 4.03 (s, 2H), 3.68 (s, 3H), 3.01 (s, 3H), 2.23 (s, 3H); 13C NMR (75 MHz, CDCl 3): δ 171.6, 146.7,
4 | J. Name., 2012, 00, 1-3
Page 4 of 7
Journal Name 129.7, 126.5, 112.5, 54.5, 51.7, 39.5, 20.2; MS (ESI): Anal. Calcd. For C11H16NO2: 194, Found: 194 (M+H+); IR (KBr, cm1 ): υ 1748, 1619, 1522, 1199. Methyl N-ethyl-N-(m-tolyl)glycinate (3j). 11 Colorless liquid (84 mg, 81% yield); 1H NMR (300 MHz, CDCl 3): δ 7.12 - 7.06 (m, 1H), 6.55 - 6.52 (m, 1H), 6.45 - 6.43 (m, 2H), 4.00 (s, 2H), 3.71 (s, 3H), 3.47 - 3.40 (m, 2H), 2.29 (s, 3H), 1.19 (t, J = 7.5 Hz, 3H); MS (ESI): Anal. Calcd. For C12H18NO2 (M+H+): 208, Found: 208; The data was in accordance with our previous report. Methyl N-benzyl-N-phenylglycinate (3k). 11 Colorless liquid (52 mg, 41% yield); 1H NMR (400 MHz, CDCl 3): δ 7.32 - 7.18 (m, 7H), 6.76 - 6.67 (m, 3H), 4.64 (s, 2H), 4.08 (s, 2H), 3.72 (s, 3H); MS (ESI): Anal. Calcd. For C 16H18NO2 (M+H+): 256, Found: 256; The data was in accordance with our previous report. Methyl N-butyl-N-phenylglycinate (3l). 11 Colorless liquid (89 mg, 80% yield); 1H NMR (400 MHz, CDCl 3): δ 7.21 - 7.17 (m, 2H), 6.71 - 6.67 (m, 1H), 6.63 - 6.60 (m, 2H), 4.01 (s, 2H), 3.70 (s, 3H), 3.36 (t, J= 8.0 Hz, 2H), 1.64 - 1.57 (m, 2H), 1.40 - 1.31 (m, 2H), 0.95 (t, J= 8.0 Hz, 3H); MS (ESI): Anal. Calcd. For C13H20NO2 (M+H+): 222, Found: 222; The data was in accordance with our previous report. Methyl N-ethyl-N-phenylglycinate (3m). 11 Colorless liquid (79 mg, 82% yield); 1H NMR (300 MHz, CDCl 3): δ 7.23 - 7.18 (m, 2H), 6.73 - 6.62 (m, 3H), 4.01 (s, 2H), 3.71 (s, 3H), 3.49 3.42 (m, 2H), 1.19 (t, J = 6.0 Hz, 3H); MS (ESI): Anal. Calcd. For C11H16NO2 (M+H+): 194, Found: 194; The data was in accordance with our previous report. Methyl N-isopropyl-N-phenylglycinate (3n). 11 Colorless liquid (73 mg, 71% yield); 1H NMR (400 MHz, CDCl 3): δ 7.23 - 7.19 (m, 2H), 6.73 - 6.66 (m, 3H), 4.19 - 4.12 (m, 1H), 3.93 (s, 2H), 3.73 (s, 3H), 1.19 (d, J = 8.0 Hz, 6H); MS (ESI): Anal. Calcd. For C12H18NO2 (M+H+): 208, Found: 208; The data was in accordance with our previous report. Methyl N-cyclohexyl-N-phenylglycinate (3o). 11 Colorless liquid (95 mg, 77% yield); 1H NMR (400 MHz, CDCl 3): δ 7.21 - 7.17 (m, 2H), 6.71 - 6.64 (m, 3H), 3.96 (s, 2H), 3.71 - 3.62 (m, 4H), 1.94-1.67 (m, 5H), 1.43-1.08 (m, 5H); MS (ESI): Anal. Calcd. For C15H22NO2 (M+H+): 248, Found: 248; The data was in accordance with our previous report. Methyl N-allyl-N-phenylglycinate (3p). 11 Colorless liquid (42 mg, 41% yield); 1H NMR (400 MHz, CDCl 3): δ 7.22 - 7.18 (m, 2H), 6.74 - 6.64 (m, 3H), 5.92 - 5.83 (m, 1H), 5.25 - 5.15 (m, 2H), 4.02 - 4.00 (m, 4H), 3.71 (s, 3H); MS (ESI): Anal. Calcd. For C12H16NO2 (M+H+): 206, Found: 206; The data was in accordance with our previous report. Methyl 2-(3,4-dihydroquinolin-1(2H)-yl)acetate (3q). 11 Colorless liquid (64 mg, 62% yield); 1H NMR (400 MHz, CDCl3): δ 7.03 - 6.95 (m, 2H), 6.63 - 6.59 (m, 1H), 6.40 - 6.38 (m, 1H), 3.99 (s, 2H), 3.70 (s, 3H), 3.38 (t, J = 6.0 Hz, 2H), 2.78 (t, J = 6.0 Hz, 2H), 2.01 - 1.95 (m, 2H); MS (ESI): Anal. Calcd. For C12H16NO2 (M+H+): 206, Found: 206; The data was in accordance with our previous report. Methyl 2-(4-phenylpiperazin-1-yl)acetate (3r). Colorless liquid (55 mg, 47% yield); 1H NMR (400 MHz, CDCl 3): δ 7.28 - 7.24 (m, 2H), 6.94 - 6.92 (m, 2H), 6.88 - 6.84 (m, 1H), 3.74 (s, 3H), 3.29 (s, 2H), 3.25 (t, J = 5.0 Hz, 4H), 2.74 (t, J = 5.0 Hz, 4H); 13C NMR (100 MHz, CDCl 3): δ 170.5, 151.1, 129.0, 119.8, 116.1, 59.3, 53.0, 51.7, 48.9; MS (ESI): Anal. Calcd. For C13H19N2O2: 235, Found: 235 (M+H+); IR (KBr, cm-1): υ 1750, 1600, 1502, 1202. Methyl 2-(4-(pyridin-2-yl)piperazin-1-yl)acetate (3s). 11 Colorless liquid (55 mg, 47% yield); 1H NMR (400 MHz,
This journal is © The Royal Society of Chemistry 2012
Organic & Biomolecular Chemistry Accepted Manuscript
ARTICLE
View Article Online
DOI: 10.1039/C5OB00109A
Organic & Biomolecular Chemistry
View Article Online
DOI: 10.1039/C5OB00109A
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
Journal Name CDCl3): δ 8.19 - 8.18 (m, 1H), 7.50 - 7.46 (m, 1H), 6.66 - 6.61 (m, 2H), 3.74 (s, 3H), 3.60 (t, J = 5.0 Hz, 4H), 3.28 (s, 2H), 2.69 (t, J = 5.0 Hz, 4H); MS (ESI): Anal. Calcd. For C12H18N3O2 (M+H+) : 236, Found: 236; The data was in accordance with our previous report. Methyl phenylglycinate (5a). 11 Colorless liquid (37 mg, 45% yield); 1H NMR (400 MHz, CDCl3): δ 7.24 - 7.17 (m, 2H), 6.77 - 6.59 (m, 3H), 3.90 (s, 2H), 3.77 (s, 3H); MS (ESI): Anal. Calcd. For C9H12NO2 (M+H+): 166, Found: 166; The data was in accordance with our previous report. Methyl p-tolylglycinate (5b). 11 Colorless liquid (37 mg, 41% yield); 1H NMR (400 MHz, CDCl3): δ 7.01 - 6.99 (m, 2H), 6.54 - 6.52 (m, 2H), 3.88 (s, 2H), 3.76 (s, 3H), 2.23 (s, 3H); MS (ESI): Anal. Calcd. For C10H14NO2 (M+H+): 180, Found: 180; The data was in accordance with our previous report. Methyl (4-chlorophenyl)glycinate (5c). 11 Colorless liquid (60 mg, 60% yield); 1H NMR (400 MHz, CDCl 3): δ 7.14 - 7.11 (m, 2H), 6.52 - 6.50 (m, 2H), 4.31 (s, 1H), 3.87 (s, 2H), 3.77 (s, 3H); MS (ESI): Anal. Calcd. For C9H1135ClNO2 (M+1+): 200, Found: 200; For C9H1137ClNO2 (M+H+): 202, Found: 202; The data was in accordance with our previous report. Methyl (4-bromophenyl)glycinate (5d). 11 Colorless liquid (57 mg, 47% yield); 1H NMR (400 MHz, CDCl3): δ 7.27 - 7.25 (m, 2H), 6.48 - 6.46 (m, 2H), 4.31 (s, 1H), 3.86 (s, 2H), 3.77 (s, 3H); MS (ESI): Anal. Calcd. For C9H1179BrNO2 (M+1+): 244, Found: 244; For C9H11 81BrNO2 (M+H+): 246, Found: 246; The data was in accordance with our previous report. Methyl (2-methoxyphenyl)glycinate (5e). 11 Colorless liquid (62 mg, 64% yield); 1H NMR (400 MHz, CDCl 3): δ 6.87 - 6.69 (m, 3H), 6.48 - 6.46 (m, 1H), 3.92 (s, 2H), 3.84 (s, 3H), 3.75 (s, 3H); MS (ESI): Anal. Calcd. For C10H14NO3 (M+H+): 196, Found: 196; The data was in accordance with our previous report. Methyl N-methyl-N-(o-tolyl)glycinate (7a). Colorless liquid (54 mg, 56% yield); 1H NMR (400 MHz, CDCl 3): δ 7.16 - 7.08 (m, 3H), 6.97 - 6.93 (m, 1H), 3.73 (s, 2H), 3.69 (s, 3H), 2.86 (s, 3H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 171.4, 150.6, 132.0, 131.2, 126.3, 123.0, 120.1, 57.2, 51.5, 41.4, 18.3; MS (ESI): Anal. Calcd. For C 11H16NO2: 194, Found: 194 (M+H+); IR (KBr, cm-1): υ 1755, 1600, 1494, 1201. Methyl N-(4-bromophenyl)-N-methylglycinate (7b). Colorless liquid (75 mg, 58% yield); 1H NMR (400 MHz, CDCl3): δ 7.29 - 7.27 (m, 2H), 6.54 - 6.52 (m, 2H), 4.02 (s, 2H), 3.69 (s, 3H), 3.01 (s, 3H); 13C NMR (100 MHz, CDCl 3): δ 171.0, 147.8, 131.8, 113.8, 109.3, 54.1, 51.9, 39.5; MS (ESI): Anal. Calcd. For C 10H1379BrNO2: 258, Found: 258 (M+H+); For C10H13 81BrNO2: 260, Found 260 (M+H+); IR (KBr, cm-1): υ 1748, 1594, 1499, 1204. Ethyl 2-(methyl(phenyl)amino)acetate (8).11 Colorless liquid (49 mg, 51% yield); 1H NMR (400 MHz, CDCl 3): δ 7.24-7.20 (m, 2H), 6.75 – 6.67 (m, 3H), 4.19- 4.14 (m, 2H), 4.04 (s, 2H), 3.05 (s, 3H), 1.23 (t, J = 8.0 Hz, 3H); MS (ESI): Anal. Calcd. For C11H16NO2: 194, Found: 194 (M+H+); The data was in accordance with our previous report.
ARTICLE a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Renai Road, 215123 Suzhou, China. Fax: (+86) 512-65880334; Tel: (+86) 512-6588-0334; E-mail: [email protected], [email protected] b Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou 213164, China. E-mail: [email protected] †Electronic Supplementary Information (ESI) available: Experimental data and spectra of compounds. See DOI: 10.1039/b000000x 1
Chem. Soc. Rev., 2011, 40, 5030; (b) J. D. Weaver, A. Recio, III, A. J. Grenning and J. A. Tunge, Chem. Rev., 2011, 111, 1846. 2
(a) L. J. Gooßen, G. Deng and L. M. Levy, Science, 2006, 313, 662; (b) S. Bhadra, W. I. Dzik and L. J. Goossen, J. Am. Chem. Soc., 2012, 134, 9938; (c) S. Bhadra, W. I. Dzik and L. J. Gooßen, Angew. Chem. Int. Ed., 2013, 52, 2959.
3
(a) A. G. Myers, D. Tanaka and M. R. Mannion, J. Am. Chem. Soc., 2002, 124, 11250; (b) D. Tanaka and A. G. Myers, Org. Lett., 2004, 6, 433; (c) D. Tanaka, S. P. Romeril and A. G. Myers, J. Am. Chem. Soc., 2005, 127, 10323.
4
(a) E. C. Burger and J. A. Tunge, J. Am. Chem. Soc., 2006, 128, 10002; (b) R. Jana, J. J. Partridge and J. A. Tunge, Angew. Chem., Int. Ed., 2011, 50, 5157; (c) S. B. Lang, K. M. O’Nele and J. A. Tunge, J. Am. Chem. Soc., 2014, 136, 13606.
5
Some recent examples reported by others, see: (a) P. Hu, M. Zhang, X. Jie and W. Su, Angew. Chem. Int. Ed., 2012, 51, 227; (b) A. Shard, N. Sharma, R. Bharti, S. Dadhwal, R. Kumar and A. K. Sinha, Angew. Chem. Int. Ed., 2012, 51, 12250; (c) D. L. Priebbenow, P. Becker and C. Bolm, Org. Lett., 2013, 15, 6155; (d) Y. Singjunla, J. Baudoux and J. Rouden, Org. Lett., 2013, 15, 5770; (e) L. Chu, C. Ohta, Z. Zuo and D. W. C. MacMillan, J. Am. Chem. Soc., 2014, 136, 10886; (f) P. Klahn, H. Erhardt, A. Kotthaus and S. F. Kirsch, Angew. Chem. Int. Ed., 2014, 53, 7913; (g) H.-X. Zhang, J. Nie, H. Cai and J.-A. Ma, Org. Lett., 2014, 16, 2542; (h) C. Li and B. Breit, J. Am. Chem. Soc., 2014, 136, 862.
6
(a) I. Shimizu, T. Yamada and J. Tsuji, Tetrahedron Lett., 1980, 21, 3199; (b) T. Tsuda, Y. Chujo, S. Nishi, K. Tawara and T. Saegusa, J. Am. Chem. Soc., 1980, 102, 6381; (c) J. Fournier, O. Lozano, C. Menozzi, S. Arseniyadis and J. Cossy, Angew. Chem. Int. Ed., 2013, 52, 1257; (d) C. J. Gartshore and D. W. Lupton, Angew. Chem. Int. Ed., 2013, 52, 4113; (e) A. Khan, R. Zheng, Y. Kan, J. Ye, J. Xing and Y. Zhang, Angew. Chem. Int. Ed., 2014, 53, 6439; (f) A. Hossian, S. Singha and R. Jana, Org. Lett., 2014, 16, 3934.
7
(a) J. Wang, B. Liu, H. Zhao and J. Wang, Organometallics, 2012, 31, 8598; (b) M. K. Ghorai, R. Talukdar and D. P. Tiwari, Org. Lett., 2014, 16, 2204.
8
Acknowledgements
For reviews on this topic, see: (a) N. Rodríguez and L. J. Goossen,
For reviews on this topic, see: (a) F. A. Carey, Organic Chemistry, 4rd ed., McGraw-Hill Higher Education, New York, 2000, pp. 1051. (b) K. Maruoka and T. Ooi, Chem. Rev., 2003, 103, 3013; (c) L.
A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and NSFC (21272165).
Aurelio, R. T. C. Brownlee and A. B. Hughes, Chem. Rev., 2004, 104, 5823; (d) Y.-C. Luo, H.-H. Zhang, Y. Wang and P.-F. Xu, Acc. Chem. Res., 2010, 43, 1317; For recent examples on amino acids synthesis, see: (e) Z. Hou, J. Wang, P. He, J. Wang, B. Qin, X. Liu, L. Lin and
Notes and references
This journal is © The Royal Society of Chemistry 2012
X. Feng, Angew. Chem. Int. Ed., 2010, 49, 4763; (f) R. Husmann, E.
J. Name ., 2012, 00, 1 -3 | 5
Organic & Biomolecular Chemistry Accepted Manuscript
Page 5 of 7
View Article Online
Organic & Biomolecular Chemistry
Page 6 of 7
DOI: 10.1039/C5OB00109A
ARTICLE
Journal Name
Sugiono, S. Mersmann, G. Raabe, M. Rueping and C. Bolm, Org. Lett., 2011, 13, 1044. For representative examples, see: (a) Y. Zhang X., Gao, K.
Organic & Biomolecular Chemistry Accepted Manuscript
9
Hardcastle and B. Wang, Chem. Eur. J., 2006, 12, 1377; (b) V. Kumar, M. P. Kaushik and A. Mazumdar, Eur. J. Org. Chem., 2008, 1910; (c) X. Piao, X. Zhang, Y. Mori, M. Koishi, A. Nakaya, S. Inoue, I. Aoki, A. Otomo and S. Yokoyama, J. Polym. Sci. Part A: Polym. Chem. 2011, 49, 47.
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
10
(a) L. Chen, E. Shi, Z. Liu, S. Chen, W. Wei, H. Li, K. Xu and X. Wan, Chem. Eur. J., 2011, 17, 4085; (b) Z. Liu, J. Zhang, S. Chen, E. Shi, Y. Xu and X. Wan, Angew. Chem. Int. Ed., 2012, 51, 3231; (c) E. Shi, Y. Shao, S. Chen, H. Hu, Z. Liu, J. Zhang and X. Wan, Org. Lett., 2012, 14, 3384; (d) J. Zhang, J. Jiang, Y. Li and X. Wan, J. Org. Chem., 2013, 78, 11366; (e) C. Zhang, C. Liu, Y. Shao, X. Bao and X. Wan, Chem. Eur. J., 2013, 19, 17917; (f) J. Zhang, Y. Shao, H. Wang, Q. Luo, J. Chen, D. Xu and X. Wan, Org. Lett., 2014, 16, 3312; (g) M. Uyanik, H. Okamoto, T. Yasui and K. Ishihara, Science, 2010, 328, 1376; (h) M. Uyanik, D. Suzuki, T. Yasui and K. Ishihara, Angew. Chem. Int. Ed., 2011, 50, 5331; (i) T. He, H. Li, P. Li and L. Wang, Chem. Commun., 2011, 47, 8946; (j) T. Froehr, C. P. Sindlinger, U. Kloeckner, P. Finkbeiner and B. J. Nachtsheim, Org. Lett., 2011, 13, 3754; (k) Y. Yan, Y. Zhang, C. Feng, Z. Zha and Z. Wang, Angew. Chem. Int. Ed., 2012, 51, 8077; (l) B. Tan, N. Toda and C. F. Barbas III, Angew. Chem. Int. Ed., 2012, 51, 12538; (m) X. Li, X. Xu and C. Zhou, Chem. Commun., 2012, 48, 12240. (n) Uyanik, M.; Hayashi, H.; Ishihara, K. Science, 2014, 345, 291. (o) Wu, X.-F.; Gong, J.-L.; Qi, X. Org. Biomol. Chem., 2014, 12, 5807.
11 J. Zhang, J. Jiang, Y. Li, Y. Zhao and X. Wan, Org. Lett., 2013, 15, 3222. 12 (a) S. Murahashi, T. Naota and K. Yonemura, J. Am. Chem. Soc., 1988, 110, 8256; (b) Y. Li, F. Jia and Z. Li, Chem. Eur. J., 2013, 19, 82; (c) Y. Kuninobu, M. Nishi and K. Takai, Chem. Commun., 2010, 46, 8860.
Table of Content
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012
Organic & Biomolecular Chemistry
Journal Name
View Article Online
DOI: 10.1039/C5OB00109A
RSCPublishing
Organic & Biomolecular Chemistry Accepted Manuscript
Page 7 of 7
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
ARTICLE
This journal is © The Royal Society of Chemistry 2013
J. Name ., 2013, 00, 1 -3 | 7
Organic & Biomolecular Chemistry
View Journal
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Zhang, Y. Shao, Y. Wang, H. Li, D. Xu and X. wan, Org. Biomol. Chem., 2015, DOI: 10.1039/C5OB00109A.
This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
www.rsc.org/obc
View Article Online
Organic & Biomolecular Chemistry
DOI: 10.1039/C5OB00109A
Journal Name
RSCPublishing
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
ARTICLE
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012, Accepted 00th January 2012 DOI: 10.1039/x0xx00000x www.rsc.org/
Transition-metal-free decarboxylation of dimethyl malonate: an efficient construction of α-amino acid esters using TBAI/TBHP Jie Zhang, a Ying Shao,*b Yaxiong Wang, a Huihuang Li, a Dongmei Xu,*a and Xiaobing Wan*a A transition-metal-free decarboxylation coupling process for the preparation of α-amino acid esters, which succeeded in merging hydrolysis/decarboxylation/nucleophilic substitution, is well described. This strategy uses commercially available inexpensive starting materials, catalysts and oxidants and has a wide substrate scope and operational simp licity.
Introduction
Table 1 Optimization of reaction conditionsa O H N
The decarboxylative functionalizations have been developed as a powerful strategy to construct new molecular skeletons. 1 During the course of the past decade, the impressive field has attracted considerable attention and been studied systematically by a variety of groups, such as those of Gooßen,2 Myers,3 Tunge,4 and others,5 thus providing many new opportunities for the convenient construction of carbon–carbon or carbon–heteroatom bonds. Related to conventional carboxylic acids as coupling reagents, ester was also an ideal alternative because of its availability, solubility and neutrality. Since the pioneering work from the groups of Tsuji 6a and Saegusa6b in the beginning of the 1980s, the palladium-catalyzed decarboxylative allylic alkylation reaction of allylic ester has been extensively applied to construct C‒C in organic synthesis. 1b,4,6 However, other common esters were rarely employed as substrates in decarboxylative reaction. 7
O
O
MeO 1a
OMe
Catalyst, Oxidant OMe
N
90 oC, 12 h
3a
2a
Entry
Catalyst
Oxidant
Yieldb (%)
1
TBAI
TBHP
2
TBAI
H2O2
3
TBAI
Oxone
4
TBAI
O2
N.D.
5
TBAI
DTBP
N.D.
6
n-Bu4NCl
TBHP
N.D.
7
n-Bu4NBr
TBHP
N.D.
8
KI
TBHP
9
TBAI
10
86 34 N.D.c
69 N.D.
TBHP
N.D.
a
Scheme 1 Our design to construct α-amino acid esters. α-Amino acids and their derivatives are of great importance in the areas of chemical, biochemical, and material science and great endeavors have been devoted to the synthesis of these compounds.8 The nucleophilic substitution of amines to αhalogenated esters constitutes the conventional approach to this ubiquitous molecules. 9 Unfortunately, this method suffered from the generation of stoichiometric halide waste. Recently, we reported a new process for the preparation of α-amino acid esters from amines and monomethyl malonate using Bu 4NI as the catalyst and tBuOOH as the oxidant, 10 including sequential iodination, decarboxylation, and nucleophilic substitution reactions.11 Combining hydrolysis reactions of dimethyl malonate and subsequent decarboxylation, we herein envision a transition-metal-free entry to α-amino acid esters under mild conditions (Scheme 1).
Results and discussion
This journal is © The Royal Society of Chemistry 2013
0.5 mmol 1a, 7.5 mmol of dimethyl malonate 2a, 20 mol% catalyst, 2.9 equiv oxidant in 1.0 mL MeCN and 1.0 mL H 2O at 90 oC for 12 h. b Isolated yield. c Not detected. We started our investigations by examining the oxidative decarboxylation coupling reaction between N-methylaniline 1a and dimethyl malonate 2a for this C‒N formation reaction. Following extensive screenings, we found that the combination of Bu 4NI (20 mol%) and tBuOOH (2.9 equiv, 70% aqueous solution) in H2O/MeCN at 90 °C for 12 h afforded the desired product 3a in the best yield of up to 86% (Table 1, entry 1). In the case of 30% aqueous H2O2 chosen as the oxidant, the yield of 3a dropped from 86% to 34% (Table 1, entry 2). Other oxidants such as oxone, molecular oxygen, and di-tert-butyl peroxide (DTBP) were also examined and the reaction did not proceed smoothly (Table 1, entries 3-5). Replacing Bu4NI with either Bu4NCl or Bu4NBr halted the formation of compound 3a (Table 1, entries 6-7). Further investigations indicated that both Bu4NI and tBuOOH are crucial to the efficient conversion and the reaction could not work in the absence of Bu4NI or tBuOOH (Table 1, entries 9-10). In addition, a
J. Name ., 2013, 00, 1 -3 | 1
Organic & Biomolecular Chemistry Accepted Manuscript
Page 1 of 7
Organic & Biomolecular Chemistry
View Article Online
Journal Name
comparable yield was obtained when KI was used as the catalyst (Table 1, entry 8). Interestingly, compared to our previous work,11 base was unnecessary for the present transformation. Table 2 Scope of secondary aminesa H N
O +
OMe
MeO
1
R1
OMe
H2O/MeCN, 90 C 3
F
N
O
Cl N
N
MeO
O
OMe
N
O
OMe
3b, yield: 81%
Cl
N
O OMe
3d, yield: 72%
N
O
OMe
3e, yield: 84%
O
NC
N
O
OMe
OMe 3g, yield: 84%
3f, yield:77%
N
OMe
3c, yield: 53%
O
O
N
R2
o
2a
OMe
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
20 mol % TBAI
O
2.9 equiv TBHP R2
OMe
3h, yield: 65%
3i, yield: trace
N
N
Ph N
O
N
O
OMe
3k, yield: 41%
3l, yield: 80%
N
N
Table 4 Scope of tertiary aromatic aminesa
O
OMe
OMe
3j, yield: 81%
N
O
with ortho, meta or para substitutents on the aromatic ring could be converted to corresponding amino acid esters in moderate to good yields. Other N-alkyl substituted aromatic amines were also found to be the effective reaction partners (products 3k-3q). A variety of functional groups, such as alkoxyl (products 3b and 3e), alkyl (products 3f, 3h and 3j), halide (products 3c, 3d and 3g), benzyl (product 3k), and allyl (product 3p) group were tolerated under the optimized conditions. It is noteworthy that aromatic amines bearing electron-donating groups were found to give better results than those with electron-withdrawing groups, presumably owing to the better nucleophilicity. As a result, only trace amount of product 3i was detected when 4-(methylamino)benzonitrile was subjected to this reaction. To our delight, two secondary aliphatic amines were also suitable reaction partners for this transformation and the corresponding products 3r and 3s were furnished in moderate yields under slightly modified conditions. To further explore the potential of the methodology, some selected primary aromatic amines had also been employed as substrates, and moderate results could be achieved when switching the solvent to H2O/EA system (Table 3, 5a-5e).
OMe 3m, yield: 82%
N
O
O
O
OMe O
OMe
OMe
OMe
3n, yield: 71%
3p, yield: 41%
3o, yield: 77%
OMe
N N
OMe
N N
O
3q, yield: 62%
O
N 3r, yield: 47%b
3s, yield: 47%b
a
All the reactions were carried out in 1.0 mL of MeCN and 1.0 mL of H2O, using 0.5 mmol of 1, 7.5 mmol of dimethyl malonate 2a, 20 mol% of TBAI and 2.9 equiv of TBHP at 90 o C for 12 h. b 0.5 mL of t BuOH and 1.5 mL of H 2O were used as solvent at 80 oC. Table 3 Scope of primary aromatic aminesa O
R1
20 mol % TBAI
O
2.9 equiv TBHP
R1 NH2
+
MeO
H2O/EA, 80 oC
4
OMe 5
2a
O
H N
O
HN
OMe
H N
O
H N
OMe
OMe
O OMe
Cl 5a, R = H, yield: 45%
H N
O
5b, R = Me, yield: 41%
H N
5c, R = Cl, yield: 60%
O
OMe
OMe
OMe
Br
5d, yield: 47%
5e, yield: 64%
a
All the reactions were carried out in 1.0 mL of ethyl acetate (EA) and 1.0 mL of H 2O, using 0.5 mmol of 4, 7.5 mmol of dimethyl malonate 2a, 20 mol% of TBAI and 2.9 equiv of TBHP at 80 oC for 12 h.
a
All the reactions were carried out in 2.0mL of H 2O, using 7.5 mmol of dimethyl malonate 2a, 0.5 mmol of 6, 20 mol% of TBAI and 4.4 equiv of TBHP at 90 oC for 12 h. In 1988, Murahashi and co-workers reported the pioneering work of the transition-metal catalyzed N-dealkylation of tertiary amines under oxidative conditions. 12a However, further transformation via dealkylation of tertiary amines was sparsely reported. Li et al. recently demonstrated an iron catalyzed amide formation by oxidative amidation between tertiary amine and aldehyde. 12b Continuing our study, 11d we envisaged that the tertiary amines could undergo a dealkylation process to generate the secondary amines in situ, which subsequently reacts with dimethyl malonate 2a to afford the desired product. Then, N, N-dimethylaniline 6a was chosen as the source of secondary amines, and to our delight, 3a could be isolated. When the amounts of tBuOOH was incresaed to 4.4 equiv and H2O was used as the only solvent, a 55% yield was obtained (Table 4, product 3a). The similar results could also be achieved using other substituted N, N-dimethylanilines (Table 4).
With the optimized conditions identified, a series of amines were applied to this methodology as shown in Table 2. N-Methylanilines
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012
Organic & Biomolecular Chemistry Accepted Manuscript
ARTICLE
R1
Page 2 of 7
DOI: 10.1039/C5OB00109A
Organic & Biomolecular Chemistry
View Article Online
DOI: 10.1039/C5OB00109A
Journal Name
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
When diethyl malonate 2b was used as the reaction partner, the corresponding product 8 was given in lower yield compared with dimethyl malonate 2a, presumably owing to the relative stability of diethyl malonate in hydrolysis (eq 1).
ARTICLE In summary, we have developed a transition-metal-free process for the synthesis of α-amino acid esters through a tandem Bu4NI-catalyzed hydrolysis/decarboxylation/nucleophlic substitution. The advantages of this protocol include a wide range of substrates, high practical convenience, and commercially available materials. Compared to our previous report, base was not necessary at all. Notably, the more accessible and more stable dimethyl malonate, instead of monomethyl malonate, were used as substrate and tertiary amines were also adaptable substrates for this protocol via a C‒ N cleavage under mild conditions. Generally, we believe that this method provides a promising complementary access to previous methodologies.
Experimental
Scheme 2 Proposed catalytic cycle.
All manipulations were carried out under air atmosphere. Column chromatography was generally performed on silica gel (300-400 mesh) and reactions were monitored by thin layer chromatography (TLC) using UV light to visualize the course of the reactions. The 1H (300MHz or 400MHz) and 13C NMR (75MHz or 100MHz) data were recorded using CDCl 3 as solvent. The chemical shifts (δ) are reported in ppm and coupling constants (J) in Hz. 1H NMR spectra was recorded with tetramethylsilane (δ= 0.00 ppm) as internal reference; 13 C NMR spectra was recorded with CDCl 3 (δ = 77.00 ppm) as internal reference. General procedure for amines 1a-1q as substrates
Scheme 3 Investigations on mechanism. Next, a plausible mechanism was proposed for the transformation as depicted in Scheme 2. Initially, I - was oxidized to hypoiodite A in the presence of TBHP, 11,10d,10g-h, 10n followed by the iodination of 3-methoxy-3-oxopropanoic acid B generated in situ from the hydrolysis of dimethyl malonate to give the intermediate C. Then, the intermediate C could form iodoacetate D via decarboxylation. Finally, the desired α-amino acids ester was delivered through the classic nucleophilic substitution of amine to D with the release of I-. Some mechanistic experiments were conducted to better understand this α-amino acid esters formation reaction (Scheme 3). The use of 2.2 equiv I2 and 4 equiv Bu4NOH10d,10g,10h,10n resulted in the desired product 3a in 54% yield (Scheme 3a), which suggested that hypoiodite generated in situ might be the key catalytic species. To find out whether the hydrolysis of dimethyl malonate played an important role in this reaction, we removed the water from the model reaction using anhydrous TBHP (5-6 M in decane) and MeCN as sole solvent (Scheme 3b). As expected, the desired product 3a could not be detected. Notably, when compound 9 was subjected to the standard conditions, no desired product 3a was isolated, thus excluding the possibility of 9 as reaction intermediate (Scheme 3c).
Conclusions
This journal is © The Royal Society of Chemistry 2012
Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (1.45 mmol), 1.0 mL of MeCN and 1.0 mL of H2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 90 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product. General procedures for amines 1r-1s as substrates Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (1.45 mmol), 0.5 mL of tBuOH and 1.5 mL of H2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 80 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product. General procedures for amines 4a-4e as substrates Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (1.45 mmol), 1.0 mL of ethyl acetate (EA) and 1.0 mL of H 2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 80 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product.
J. Name ., 2012, 00, 1 -3 | 3
Organic & Biomolecular Chemistry Accepted Manuscript
Page 3 of 7
Organic & Biomolecular Chemistry
General procedures for tertiary amines as substrates
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
Amine (0.5 mmol), dimethyl malonate (7.5 mmol), Bu 4NI (0.1 mmol, 20 mol %), TBHP (2.2 mmol), 2.0 mL of H 2O were added to a test tube under air. The reaction mixture was heated in an oil bath at 90 oC for 12 h. It was then quenched with saturated Na 2SO3 solution (removal of excess TBHP) and extracted with ethyl acetate. The organic layer was combined and removed under vacuum followed by flash silica gel column chromatographic purification using a mixture of petroleum ether and ethyl acetate afforded the desired product. Methyl N-methyl-N-phenylglycinate (3a). 11 Colorless liquid (77 mg, 86% yield for amine 1a; 49 mg, 55% yield for amine 6a); 1H NMR (300 MHz, CDCl 3): δ 7.24 - 7.19 (m, 2H), 6.76 6.65 (m, 3H), 4.04 (s, 2H), 3.68 (s, 3H), 3.03 (s, 3H); MS (ESI): Anal. Calcd. For C10H14NO2: 180, Found: 180(M+H+); The data was in accordance with our previous report. Methyl N-(2-methoxyphenyl)-N-methylglycinate (3b). 11 Colorless liquid (85 mg, 81% yield); 1H NMR (400 MHz, CDCl3): δ 7.02 - 7.00 (m, 1H), 6.96 - 6.88 (m, 2H), 6.83 - 6.81 (m, 1H), 4.00 (s, 2H), 3.82 (s, 3H), 3.66 (s, 3H), 2.96 (s, 3H); MS (ESI): Anal. Calcd. For C11H16NO3 (M+H+): 210, Found: 210; The data was in accordance with our previous report. Methyl N-(2-fluorophenyl)-N-methylglycinate (3c). 11 1 Colorless liquid (52 mg, 53% yield); H NMR (400 MHz, CDCl3): δ 7.04 - 6.91 (m, 3H), 6.85 - 6.79 (m, 1H), 4.02 (s, 2H), 3.67 (s, 3H), 2.98 (s, 3H); MS (ESI): Anal. Calcd. For C10H13FNO2 (M+H+): 198, Found: 198; The data was in accordance with our previous report. Methyl N-(3-chlorophenyl)-N-methylglycinate (3d). 11 Colorless liquid (77 mg, 72% yield for amine 1d; 57 mg, 53% yield for amine 6c); 1H NMR (400 MHz, CDCl 3): δ 7.13 - 7.09 (m, 1H), 6.71 - 6.64 (m, 2H), 6.53 - 6.50 (m, 1H), 4.03 (s, 2H), 3.71 (s, 3H), 3.02 (s, 3H); MS (ESI): Anal. Calcd. For C10H13 35ClNO2 (M+H+): 214, Found: 214; For C10H13 37ClNO2 (M+H+): 216, Found: 216; The data was in accordance with our previous report. Methyl N-(3-methoxyphenyl)-N-methylglycinate (3e). Colorless liquid (88 mg, 84% yield); 1H NMR (400 MHz, CDCl3): δ 7.14 - 7.10 (m, 1H), 6.32 - 6.22 (m, 3H), 4.03 (s, 2H), 3.76 (s, 3H), 3.69 (s, 3H), 3.03 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 171.3, 160.6, 150.1, 129.8, 105.2, 102.0, 98.9, 54.9, 54.2, 51.7, 39.4; MS (ESI): Anal. Calcd. For C 11H16NO3: 210, Found: 210 (M+H+); IR (KBr, cm-1): υ 1750, 1613, 1502, 1201. Methyl N-methyl-N-(m-tolyl)glycinate (3f). Colorless liquid (74 mg, 77% yield for amine 1f, 50 mg, 52% yield for amine 6c); 1H NMR (400 MHz, CDCl 3): δ 7.13 - 7.09 (m, 1H), 6.58 6.56 (m, 1H), 6.50 - 6.47 (m, 2H), 4.04 (s, 2H), 3.70 (s, 3H), 3.03 (s, 3H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl 3): δ 171.5, 148.8, 138.8, 129.0, 118.3, 113.0, 109.4, 54.3, 51.8, 39.4, 21.8; MS (ESI): Anal. Calcd. For C 11H16NO2: 194, Found: 194 (M+H+); IR (KBr, cm-1): υ 1750, 1605, 1499, 1202. Methyl N-(4-chlorophenyl)-N-methylglycinate (3g). 11 1 Colorless liquid (90 mg, 84% yield); H NMR (300 MHz, CDCl3): δ 7.17 - 7.14 (m, 2H), 6.60 - 6.57 (m, 2H), 4.03 (s, 2H), 3.70 (s, 3H), 3.02 (s, 3H); MS (ESI): Anal. Calcd. For C10H13 35ClNO2 (M+H+): 214, Found: 214; For C10H13 37ClNO2 (M+H+): 216, Found: 216; The data was in accordance with our previous report. Methyl N-methyl-N-(p-tolyl)glycinate (3h). Colorless liquid (63 mg, 65% yield); 1H NMR (300 MHz, CDCl 3): δ 7.04 - 7.01 (m, 2H), 6.62 - 6.59 (m, 2H), 4.03 (s, 2H), 3.68 (s, 3H), 3.01 (s, 3H), 2.23 (s, 3H); 13C NMR (75 MHz, CDCl 3): δ 171.6, 146.7,
4 | J. Name., 2012, 00, 1-3
Page 4 of 7
Journal Name 129.7, 126.5, 112.5, 54.5, 51.7, 39.5, 20.2; MS (ESI): Anal. Calcd. For C11H16NO2: 194, Found: 194 (M+H+); IR (KBr, cm1 ): υ 1748, 1619, 1522, 1199. Methyl N-ethyl-N-(m-tolyl)glycinate (3j). 11 Colorless liquid (84 mg, 81% yield); 1H NMR (300 MHz, CDCl 3): δ 7.12 - 7.06 (m, 1H), 6.55 - 6.52 (m, 1H), 6.45 - 6.43 (m, 2H), 4.00 (s, 2H), 3.71 (s, 3H), 3.47 - 3.40 (m, 2H), 2.29 (s, 3H), 1.19 (t, J = 7.5 Hz, 3H); MS (ESI): Anal. Calcd. For C12H18NO2 (M+H+): 208, Found: 208; The data was in accordance with our previous report. Methyl N-benzyl-N-phenylglycinate (3k). 11 Colorless liquid (52 mg, 41% yield); 1H NMR (400 MHz, CDCl 3): δ 7.32 - 7.18 (m, 7H), 6.76 - 6.67 (m, 3H), 4.64 (s, 2H), 4.08 (s, 2H), 3.72 (s, 3H); MS (ESI): Anal. Calcd. For C 16H18NO2 (M+H+): 256, Found: 256; The data was in accordance with our previous report. Methyl N-butyl-N-phenylglycinate (3l). 11 Colorless liquid (89 mg, 80% yield); 1H NMR (400 MHz, CDCl 3): δ 7.21 - 7.17 (m, 2H), 6.71 - 6.67 (m, 1H), 6.63 - 6.60 (m, 2H), 4.01 (s, 2H), 3.70 (s, 3H), 3.36 (t, J= 8.0 Hz, 2H), 1.64 - 1.57 (m, 2H), 1.40 - 1.31 (m, 2H), 0.95 (t, J= 8.0 Hz, 3H); MS (ESI): Anal. Calcd. For C13H20NO2 (M+H+): 222, Found: 222; The data was in accordance with our previous report. Methyl N-ethyl-N-phenylglycinate (3m). 11 Colorless liquid (79 mg, 82% yield); 1H NMR (300 MHz, CDCl 3): δ 7.23 - 7.18 (m, 2H), 6.73 - 6.62 (m, 3H), 4.01 (s, 2H), 3.71 (s, 3H), 3.49 3.42 (m, 2H), 1.19 (t, J = 6.0 Hz, 3H); MS (ESI): Anal. Calcd. For C11H16NO2 (M+H+): 194, Found: 194; The data was in accordance with our previous report. Methyl N-isopropyl-N-phenylglycinate (3n). 11 Colorless liquid (73 mg, 71% yield); 1H NMR (400 MHz, CDCl 3): δ 7.23 - 7.19 (m, 2H), 6.73 - 6.66 (m, 3H), 4.19 - 4.12 (m, 1H), 3.93 (s, 2H), 3.73 (s, 3H), 1.19 (d, J = 8.0 Hz, 6H); MS (ESI): Anal. Calcd. For C12H18NO2 (M+H+): 208, Found: 208; The data was in accordance with our previous report. Methyl N-cyclohexyl-N-phenylglycinate (3o). 11 Colorless liquid (95 mg, 77% yield); 1H NMR (400 MHz, CDCl 3): δ 7.21 - 7.17 (m, 2H), 6.71 - 6.64 (m, 3H), 3.96 (s, 2H), 3.71 - 3.62 (m, 4H), 1.94-1.67 (m, 5H), 1.43-1.08 (m, 5H); MS (ESI): Anal. Calcd. For C15H22NO2 (M+H+): 248, Found: 248; The data was in accordance with our previous report. Methyl N-allyl-N-phenylglycinate (3p). 11 Colorless liquid (42 mg, 41% yield); 1H NMR (400 MHz, CDCl 3): δ 7.22 - 7.18 (m, 2H), 6.74 - 6.64 (m, 3H), 5.92 - 5.83 (m, 1H), 5.25 - 5.15 (m, 2H), 4.02 - 4.00 (m, 4H), 3.71 (s, 3H); MS (ESI): Anal. Calcd. For C12H16NO2 (M+H+): 206, Found: 206; The data was in accordance with our previous report. Methyl 2-(3,4-dihydroquinolin-1(2H)-yl)acetate (3q). 11 Colorless liquid (64 mg, 62% yield); 1H NMR (400 MHz, CDCl3): δ 7.03 - 6.95 (m, 2H), 6.63 - 6.59 (m, 1H), 6.40 - 6.38 (m, 1H), 3.99 (s, 2H), 3.70 (s, 3H), 3.38 (t, J = 6.0 Hz, 2H), 2.78 (t, J = 6.0 Hz, 2H), 2.01 - 1.95 (m, 2H); MS (ESI): Anal. Calcd. For C12H16NO2 (M+H+): 206, Found: 206; The data was in accordance with our previous report. Methyl 2-(4-phenylpiperazin-1-yl)acetate (3r). Colorless liquid (55 mg, 47% yield); 1H NMR (400 MHz, CDCl 3): δ 7.28 - 7.24 (m, 2H), 6.94 - 6.92 (m, 2H), 6.88 - 6.84 (m, 1H), 3.74 (s, 3H), 3.29 (s, 2H), 3.25 (t, J = 5.0 Hz, 4H), 2.74 (t, J = 5.0 Hz, 4H); 13C NMR (100 MHz, CDCl 3): δ 170.5, 151.1, 129.0, 119.8, 116.1, 59.3, 53.0, 51.7, 48.9; MS (ESI): Anal. Calcd. For C13H19N2O2: 235, Found: 235 (M+H+); IR (KBr, cm-1): υ 1750, 1600, 1502, 1202. Methyl 2-(4-(pyridin-2-yl)piperazin-1-yl)acetate (3s). 11 Colorless liquid (55 mg, 47% yield); 1H NMR (400 MHz,
This journal is © The Royal Society of Chemistry 2012
Organic & Biomolecular Chemistry Accepted Manuscript
ARTICLE
View Article Online
DOI: 10.1039/C5OB00109A
Organic & Biomolecular Chemistry
View Article Online
DOI: 10.1039/C5OB00109A
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
Journal Name CDCl3): δ 8.19 - 8.18 (m, 1H), 7.50 - 7.46 (m, 1H), 6.66 - 6.61 (m, 2H), 3.74 (s, 3H), 3.60 (t, J = 5.0 Hz, 4H), 3.28 (s, 2H), 2.69 (t, J = 5.0 Hz, 4H); MS (ESI): Anal. Calcd. For C12H18N3O2 (M+H+) : 236, Found: 236; The data was in accordance with our previous report. Methyl phenylglycinate (5a). 11 Colorless liquid (37 mg, 45% yield); 1H NMR (400 MHz, CDCl3): δ 7.24 - 7.17 (m, 2H), 6.77 - 6.59 (m, 3H), 3.90 (s, 2H), 3.77 (s, 3H); MS (ESI): Anal. Calcd. For C9H12NO2 (M+H+): 166, Found: 166; The data was in accordance with our previous report. Methyl p-tolylglycinate (5b). 11 Colorless liquid (37 mg, 41% yield); 1H NMR (400 MHz, CDCl3): δ 7.01 - 6.99 (m, 2H), 6.54 - 6.52 (m, 2H), 3.88 (s, 2H), 3.76 (s, 3H), 2.23 (s, 3H); MS (ESI): Anal. Calcd. For C10H14NO2 (M+H+): 180, Found: 180; The data was in accordance with our previous report. Methyl (4-chlorophenyl)glycinate (5c). 11 Colorless liquid (60 mg, 60% yield); 1H NMR (400 MHz, CDCl 3): δ 7.14 - 7.11 (m, 2H), 6.52 - 6.50 (m, 2H), 4.31 (s, 1H), 3.87 (s, 2H), 3.77 (s, 3H); MS (ESI): Anal. Calcd. For C9H1135ClNO2 (M+1+): 200, Found: 200; For C9H1137ClNO2 (M+H+): 202, Found: 202; The data was in accordance with our previous report. Methyl (4-bromophenyl)glycinate (5d). 11 Colorless liquid (57 mg, 47% yield); 1H NMR (400 MHz, CDCl3): δ 7.27 - 7.25 (m, 2H), 6.48 - 6.46 (m, 2H), 4.31 (s, 1H), 3.86 (s, 2H), 3.77 (s, 3H); MS (ESI): Anal. Calcd. For C9H1179BrNO2 (M+1+): 244, Found: 244; For C9H11 81BrNO2 (M+H+): 246, Found: 246; The data was in accordance with our previous report. Methyl (2-methoxyphenyl)glycinate (5e). 11 Colorless liquid (62 mg, 64% yield); 1H NMR (400 MHz, CDCl 3): δ 6.87 - 6.69 (m, 3H), 6.48 - 6.46 (m, 1H), 3.92 (s, 2H), 3.84 (s, 3H), 3.75 (s, 3H); MS (ESI): Anal. Calcd. For C10H14NO3 (M+H+): 196, Found: 196; The data was in accordance with our previous report. Methyl N-methyl-N-(o-tolyl)glycinate (7a). Colorless liquid (54 mg, 56% yield); 1H NMR (400 MHz, CDCl 3): δ 7.16 - 7.08 (m, 3H), 6.97 - 6.93 (m, 1H), 3.73 (s, 2H), 3.69 (s, 3H), 2.86 (s, 3H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 171.4, 150.6, 132.0, 131.2, 126.3, 123.0, 120.1, 57.2, 51.5, 41.4, 18.3; MS (ESI): Anal. Calcd. For C 11H16NO2: 194, Found: 194 (M+H+); IR (KBr, cm-1): υ 1755, 1600, 1494, 1201. Methyl N-(4-bromophenyl)-N-methylglycinate (7b). Colorless liquid (75 mg, 58% yield); 1H NMR (400 MHz, CDCl3): δ 7.29 - 7.27 (m, 2H), 6.54 - 6.52 (m, 2H), 4.02 (s, 2H), 3.69 (s, 3H), 3.01 (s, 3H); 13C NMR (100 MHz, CDCl 3): δ 171.0, 147.8, 131.8, 113.8, 109.3, 54.1, 51.9, 39.5; MS (ESI): Anal. Calcd. For C 10H1379BrNO2: 258, Found: 258 (M+H+); For C10H13 81BrNO2: 260, Found 260 (M+H+); IR (KBr, cm-1): υ 1748, 1594, 1499, 1204. Ethyl 2-(methyl(phenyl)amino)acetate (8).11 Colorless liquid (49 mg, 51% yield); 1H NMR (400 MHz, CDCl 3): δ 7.24-7.20 (m, 2H), 6.75 – 6.67 (m, 3H), 4.19- 4.14 (m, 2H), 4.04 (s, 2H), 3.05 (s, 3H), 1.23 (t, J = 8.0 Hz, 3H); MS (ESI): Anal. Calcd. For C11H16NO2: 194, Found: 194 (M+H+); The data was in accordance with our previous report.
ARTICLE a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Renai Road, 215123 Suzhou, China. Fax: (+86) 512-65880334; Tel: (+86) 512-6588-0334; E-mail: [email protected], [email protected] b Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou 213164, China. E-mail: [email protected] †Electronic Supplementary Information (ESI) available: Experimental data and spectra of compounds. See DOI: 10.1039/b000000x 1
Chem. Soc. Rev., 2011, 40, 5030; (b) J. D. Weaver, A. Recio, III, A. J. Grenning and J. A. Tunge, Chem. Rev., 2011, 111, 1846. 2
(a) L. J. Gooßen, G. Deng and L. M. Levy, Science, 2006, 313, 662; (b) S. Bhadra, W. I. Dzik and L. J. Goossen, J. Am. Chem. Soc., 2012, 134, 9938; (c) S. Bhadra, W. I. Dzik and L. J. Gooßen, Angew. Chem. Int. Ed., 2013, 52, 2959.
3
(a) A. G. Myers, D. Tanaka and M. R. Mannion, J. Am. Chem. Soc., 2002, 124, 11250; (b) D. Tanaka and A. G. Myers, Org. Lett., 2004, 6, 433; (c) D. Tanaka, S. P. Romeril and A. G. Myers, J. Am. Chem. Soc., 2005, 127, 10323.
4
(a) E. C. Burger and J. A. Tunge, J. Am. Chem. Soc., 2006, 128, 10002; (b) R. Jana, J. J. Partridge and J. A. Tunge, Angew. Chem., Int. Ed., 2011, 50, 5157; (c) S. B. Lang, K. M. O’Nele and J. A. Tunge, J. Am. Chem. Soc., 2014, 136, 13606.
5
Some recent examples reported by others, see: (a) P. Hu, M. Zhang, X. Jie and W. Su, Angew. Chem. Int. Ed., 2012, 51, 227; (b) A. Shard, N. Sharma, R. Bharti, S. Dadhwal, R. Kumar and A. K. Sinha, Angew. Chem. Int. Ed., 2012, 51, 12250; (c) D. L. Priebbenow, P. Becker and C. Bolm, Org. Lett., 2013, 15, 6155; (d) Y. Singjunla, J. Baudoux and J. Rouden, Org. Lett., 2013, 15, 5770; (e) L. Chu, C. Ohta, Z. Zuo and D. W. C. MacMillan, J. Am. Chem. Soc., 2014, 136, 10886; (f) P. Klahn, H. Erhardt, A. Kotthaus and S. F. Kirsch, Angew. Chem. Int. Ed., 2014, 53, 7913; (g) H.-X. Zhang, J. Nie, H. Cai and J.-A. Ma, Org. Lett., 2014, 16, 2542; (h) C. Li and B. Breit, J. Am. Chem. Soc., 2014, 136, 862.
6
(a) I. Shimizu, T. Yamada and J. Tsuji, Tetrahedron Lett., 1980, 21, 3199; (b) T. Tsuda, Y. Chujo, S. Nishi, K. Tawara and T. Saegusa, J. Am. Chem. Soc., 1980, 102, 6381; (c) J. Fournier, O. Lozano, C. Menozzi, S. Arseniyadis and J. Cossy, Angew. Chem. Int. Ed., 2013, 52, 1257; (d) C. J. Gartshore and D. W. Lupton, Angew. Chem. Int. Ed., 2013, 52, 4113; (e) A. Khan, R. Zheng, Y. Kan, J. Ye, J. Xing and Y. Zhang, Angew. Chem. Int. Ed., 2014, 53, 6439; (f) A. Hossian, S. Singha and R. Jana, Org. Lett., 2014, 16, 3934.
7
(a) J. Wang, B. Liu, H. Zhao and J. Wang, Organometallics, 2012, 31, 8598; (b) M. K. Ghorai, R. Talukdar and D. P. Tiwari, Org. Lett., 2014, 16, 2204.
8
Acknowledgements
For reviews on this topic, see: (a) N. Rodríguez and L. J. Goossen,
For reviews on this topic, see: (a) F. A. Carey, Organic Chemistry, 4rd ed., McGraw-Hill Higher Education, New York, 2000, pp. 1051. (b) K. Maruoka and T. Ooi, Chem. Rev., 2003, 103, 3013; (c) L.
A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and NSFC (21272165).
Aurelio, R. T. C. Brownlee and A. B. Hughes, Chem. Rev., 2004, 104, 5823; (d) Y.-C. Luo, H.-H. Zhang, Y. Wang and P.-F. Xu, Acc. Chem. Res., 2010, 43, 1317; For recent examples on amino acids synthesis, see: (e) Z. Hou, J. Wang, P. He, J. Wang, B. Qin, X. Liu, L. Lin and
Notes and references
This journal is © The Royal Society of Chemistry 2012
X. Feng, Angew. Chem. Int. Ed., 2010, 49, 4763; (f) R. Husmann, E.
J. Name ., 2012, 00, 1 -3 | 5
Organic & Biomolecular Chemistry Accepted Manuscript
Page 5 of 7
View Article Online
Organic & Biomolecular Chemistry
Page 6 of 7
DOI: 10.1039/C5OB00109A
ARTICLE
Journal Name
Sugiono, S. Mersmann, G. Raabe, M. Rueping and C. Bolm, Org. Lett., 2011, 13, 1044. For representative examples, see: (a) Y. Zhang X., Gao, K.
Organic & Biomolecular Chemistry Accepted Manuscript
9
Hardcastle and B. Wang, Chem. Eur. J., 2006, 12, 1377; (b) V. Kumar, M. P. Kaushik and A. Mazumdar, Eur. J. Org. Chem., 2008, 1910; (c) X. Piao, X. Zhang, Y. Mori, M. Koishi, A. Nakaya, S. Inoue, I. Aoki, A. Otomo and S. Yokoyama, J. Polym. Sci. Part A: Polym. Chem. 2011, 49, 47.
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
10
(a) L. Chen, E. Shi, Z. Liu, S. Chen, W. Wei, H. Li, K. Xu and X. Wan, Chem. Eur. J., 2011, 17, 4085; (b) Z. Liu, J. Zhang, S. Chen, E. Shi, Y. Xu and X. Wan, Angew. Chem. Int. Ed., 2012, 51, 3231; (c) E. Shi, Y. Shao, S. Chen, H. Hu, Z. Liu, J. Zhang and X. Wan, Org. Lett., 2012, 14, 3384; (d) J. Zhang, J. Jiang, Y. Li and X. Wan, J. Org. Chem., 2013, 78, 11366; (e) C. Zhang, C. Liu, Y. Shao, X. Bao and X. Wan, Chem. Eur. J., 2013, 19, 17917; (f) J. Zhang, Y. Shao, H. Wang, Q. Luo, J. Chen, D. Xu and X. Wan, Org. Lett., 2014, 16, 3312; (g) M. Uyanik, H. Okamoto, T. Yasui and K. Ishihara, Science, 2010, 328, 1376; (h) M. Uyanik, D. Suzuki, T. Yasui and K. Ishihara, Angew. Chem. Int. Ed., 2011, 50, 5331; (i) T. He, H. Li, P. Li and L. Wang, Chem. Commun., 2011, 47, 8946; (j) T. Froehr, C. P. Sindlinger, U. Kloeckner, P. Finkbeiner and B. J. Nachtsheim, Org. Lett., 2011, 13, 3754; (k) Y. Yan, Y. Zhang, C. Feng, Z. Zha and Z. Wang, Angew. Chem. Int. Ed., 2012, 51, 8077; (l) B. Tan, N. Toda and C. F. Barbas III, Angew. Chem. Int. Ed., 2012, 51, 12538; (m) X. Li, X. Xu and C. Zhou, Chem. Commun., 2012, 48, 12240. (n) Uyanik, M.; Hayashi, H.; Ishihara, K. Science, 2014, 345, 291. (o) Wu, X.-F.; Gong, J.-L.; Qi, X. Org. Biomol. Chem., 2014, 12, 5807.
11 J. Zhang, J. Jiang, Y. Li, Y. Zhao and X. Wan, Org. Lett., 2013, 15, 3222. 12 (a) S. Murahashi, T. Naota and K. Yonemura, J. Am. Chem. Soc., 1988, 110, 8256; (b) Y. Li, F. Jia and Z. Li, Chem. Eur. J., 2013, 19, 82; (c) Y. Kuninobu, M. Nishi and K. Takai, Chem. Commun., 2010, 46, 8860.
Table of Content
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012
Organic & Biomolecular Chemistry
Journal Name
View Article Online
DOI: 10.1039/C5OB00109A
RSCPublishing
Organic & Biomolecular Chemistry Accepted Manuscript
Page 7 of 7
Published on 11 February 2015. Downloaded by Mahidol University on 11/02/2015 13:02:49.
ARTICLE
This journal is © The Royal Society of Chemistry 2013
J. Name ., 2013, 00, 1 -3 | 7
