DOI: 10.1002/chem.201406031
Communication
& C H Activation
A Convenient Synthesis of N-Aryl Benzamides by RhodiumCatalyzed ortho-Amidation and Decarboxylation of Benzoic Acids Xian-Ying Shi,*[a] Ke-Yan Liu,[a] Juan Fan,[a] Xue-Fen Dong,[a] Jun-Fa Wei,[a] and Chao-Jun Li*[b] alkenyl C H bond to isocyanates with subsequent cyclization, respectively.[10] Very recently, Ackermann and co-workers developed a versatile route to phthalimides by RuII-catalyzed C H activation of amides with isocyanates.[11] In all of these reports, the amide group was introduced ortho to the directing group, while the directing group remains in place “permanently”. Transition metal-catalyzed decarboxylative cross-coupling reactions have recently emerged as a new and important category of organic transformation that finds versatile applications in the construction of C C and C heteroatom bonds.[12] However, the new C C or C heteroatom bond is usually formed at the original position of the carboxylate group (Scheme 1 a) and
Abstract: The rhodium-catalyzed amidation of substituted benzoic acids with isocyanates by directed C H functionalization followed by decarboxylation to afford the corresponding N-aryl benzamides is demonstrated, in which the carboxylate serves as a unique, removable directing group. Notably, less common meta-substituted N-aryl benzamides are generated readily from more accessible paraor ortho-substituted groups by employing this strategy.
In recent decades, transition metal-catalyzed C H functionalization reactions have emerged as a powerful method in organic synthesis.[1] Chelation-assisted C H bond activation and subsequent addition to unsaturated molecules have offered many efficient syntheses in an atom-economic fashion.[2] The direct insertion of C H to unsaturated alkene and alkyne derivatives has been extensively investigated;[3] whereas analogous additions across polarized C N multiple bonds have seen considerably less progress. However, the installment of nitrogen-based functional groups into molecules through the direct addition of C H bonds to unsaturated C N multiple bonds represents a worthwhile pursuit with profound synthetic potentials.[4] In particular, the direct insertion of C H bonds into isocyanates is highly desirable since it can effectively provide synthetically valuable amide moieties,[5] which not only represent an important structural motif present in many natural products, polymers, pharmaceuticals, and biological systems,[6] but also are of great importance as intermediates for the preparation of various useful compounds.[7] In this context, Cheng and co-workers illustrated an efficient RuII-catalyzed amidation of 2-arylpyridines with isocyanates by C H bond activation.[8] A RhIII-catalyzed protocol for amidation of anilide and enamide C H bonds with isocyanates was developed by Ellman and co-workers.[9] The groups of Takai and Li reported ReII and RhIII-catalyzed addition of an
Scheme 1. Decarboxylative C C cross-coupling reactions.
there are only few reports using carboxylic acids as a traceless directing group (Scheme 1 b).[12b, 13, 14] In the course of our study on the cascade cyclization of o-toluic acid with phenyl isocyanate,[15] we unexpectedly observed that the acid-free 3-methylN-phenylbenzamide was generated under rhodium catalysis (Scheme 1 c). This finding indicates that the reaction involved a carboxyl-directed ortho-amidation of o-toluic acid via C H functionalization followed by decarboxylation. Namely, the carboxy group acted as a removable ortho-directing group. We reasoned that, by employing this strategy, N-aryl benzamides with more difficult substitutions could be obtained readily
[a] Dr. X.-Y. Shi, K.-Y. Liu, J. Fan, X.-F. Dong, Prof. Dr. J.-F. Wei Key Laboratory of Applied Surface and Colloid Chemistry (Ministry of Education), Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710062 (P. R. China) E-mail: [email protected] [b] Prof. Dr. C.-J. Li Department of Chemistry, McGill University Montreal, QC, H3 A 0B8 (Canada) E-mail: [email protected] Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201406031. Chem. Eur. J. 2014, 20, 1 – 5
These are not the final page numbers! ÞÞ
1
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
Communication from other substituted benzoic acids, which are conveniently more accessible. Herein, we present the convenient synthesis of N-aryl benzamides by rhodium-catalyzed ortho-amidation and decarboxylation of benzoic acids. To understand the nature of this reaction and to optimize the reaction conditions, different solvents were first examined, given the importance of solvent effects in catalytic reactions (Table 1, entries 1–9). Solvent screenings revealed that dioxane provided a slightly higher yield than THF, chlorobenzene, tolu-
K2HPO4 and Cu2O was used in the reaction system (Table 1, entry 20). Having established the optimized reaction conditions, the substrate scope was examined with respect to the substituted benzoic acids (Table 2). No desired product was isolated using 2-nitrobenzoic acid, bearing a strong electron-withdrawing
Table 2. Substrate scope for the C H functionalization–decarboxylation Reaction.[a]
Table 1. Selected results for optimizing reaction conditions.[a]
Entry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Additive (equiv)
Solvent
Yield [%][b]
K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(2.0) — Na2HPO4(2.0) KH2PO4(2.0) NaH2PO4(2.0) K3PO4(2.0) K2CO3(2.0) Na2CO3(2.0) Li2CO3(21.0) Ag2CO3(2.0) K2HPO4 (2.0)/Cu2O (0.15)
THF C6H5Cl toluene o-xylene dioxane DCE DMF CH3CN t-BuOH dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane
13 11 10 11 23 ND[c] ND ND ND 48 ND ND trace ND 12 25 40 29 14 65
[a] Reactions were carried out with o-toluic acid (0.1 mmol), phenylisocyanate (0.2 mmol), [{Cp*RhCl2}2] (5 mol %), additives, and solvent (0.5 mL) at 150 8C for 24 h, under argon in pressure tubes; [b] determined by 1H NMR spectroscopy of the crude reaction mixture using mesitylene as internal standard; [c] ND = not detected.
[a] Reactions were carried out with acids (0.2 mmol), isocyanates (0.4 mmol), [{Cp*RhCl2}2] (5 mol %), dioxane (0.5 mL), K2HPO4 (2.0 equiv), Cu2O (0.15 equiv), 150 8C, 24 h. Yield of isolated product was reported.
ene, or o-xylene, and no target product was detected when dichloroethane (DCE), DMF, acetonitrile, or tert-butanol were used as solvent. The moderate yield of 3 a could be enhanced to 48 % by increasing the amount of K2HPO4 to 2.0 equivalents. No desired product was formed in the absence of K2HPO4 (Table 1, entry 11), which suggested that the choice of salt is crucial for the success of the present catalytic reaction. Therefore, a series of salts was also examined for the reaction. Disappointingly, when other alkali phosphates such as Na2HPO4, KH2PO4, NaH2PO4, and K3PO4 were employed, either no desired product or only trace amounts thereof was formed (Table 1, entries 12–15). The use of carbonates also provided the desired product with decreased yield compared to K2HPO4 (Table 1, entries 16–19). Given that Cu2O is known to promote the decarboxylation,[13i, 16] different amounts of Cu2O were introduced to optimize the formation of this product. Finally, the yield of the product was further improved to 65 % when a mixture of &
&
Chem. Eur. J. 2014, 20, 1 – 5
www.chemeurj.org
group, which suggests that the parent carboxy group and the additional electron-withdrawing group render the aryl ring highly electron-deficient and retard the attacking of electrophilic rhodium. The location of substituents on the parent benzoic acid has a strong influence on the product yield. For example, o-methoxybenzoic acid afforded only 30 % yield of the product, which can be attributed to deactivation resulting from the coordination between an electron-rich heteroatom and rhodium. Compared with ortho-substituted benzoic acids, those bearing substituents at the para position were readily converted into the corresponding products in higher yields (Table 2; 3 a vs. 3 d, 3 b vs. 3 e, 3 c vs. 3 f). Meta-substituted benzoic acids also reacted smoothly to afford the corresponding products in high yields and generated two regioisomers (Table 2; 3 h and 3 h’), due to the two possible C H bond activation sites at C2 and C6. The amide formation occurred selectively para to the sub2
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Communication stituent, which illustrated that the reaction was mainly under steric control. This transformation tolerated dual substitution and 2,4-dimethylbenzoic acid gave the highest yield of the corresponding product (Table 2; 3 i–l). To further explore the substrate scope and limitations of this process, the reactions between 2,4-dimethylbenzoic acid and various isocyanates were tested (Table 2). 3-methyl, 4-methyl, and 3,5-dimethyl phenyl isocyanates underwent C H activation and a decarboxylation reaction effectively with 2,4-dimethylbenzoic acid, producing the corresponding products in 74 %, 80 %, and 77 % yields, respectively (3 m, 3 n, 3 p). In the presence of electron-withdrawing groups such as Cl and Br, the desired products were also obtained, although the yields were somewhat decreased (3 o, 3 q, 3 r). Particularly noteworthy was that halo groups (Cl, Br) on the aromatic ring of isocyanate remained intact in the product, which provides the possibility for further useful transformations through common cross-coupling strategies. Thus, as a proof-of-concept, using 3 q as the reactant, a further transformation of the product by employing the Suzuki reaction afforded the product 4 q in 38 % yield (Scheme 2).[17] Based on known rhodium-catalyzed directing-group-assisted C H bond activation reactions[18] and metal-mediated decarboxylation reactions,[19] a tentative mechanism to rationalize this reaction is depicted in Scheme 3. Dissociation of the dimer precatalyst [{Cp*RhCl2}2] provides the coordinatively unsaturated monomer. With the help of K2HPO4, coordination of the
rhodium species to the carboxylic oxygen atom and subsequent ortho C H activation affords a five-membered rhodacyclic intermediate B, releasing one equivalent of proton at the same time. Then, isocyanate is coordinated to B at Rh to form C, followed by the insertion of the isocyanate into the Rh C bond of C to generate the seven-membered rhodium alkoxide D. Protonation of D by HCl affords the intermediate E and regenerates the active RhIII species for the next cycle. Finally, decarboxylation of E followed by protonation provides the final product. In summary, we have succeeded in preparing a series of Naryl benzamides from readily available benzoic acids and isocyanates through regiospecific amidation of aromatic ortho-C H groups with concomitant decarboxylation. In these reactions, the carboxy function effectively serves as a removable directing group. Notably, less common meta-substituted N-aryl benzamides can arise readily from more accessible para- or orthosubstituted groups by employing this strategy.
Experimental Section An oven-dried reaction vessel was charged with [{Cp*RhCl2}2] (6.2 mg, 5 mol %, 0.01 mmol), acid 1 (0.2 mmol), isocyanate 2 (0.4 mmol), K2HPO4 (69.6 mg, 0.4 mmol), Cu2O (4.4 mg, 0.06 mmol). After the tube was evacuated and purged with argon three times, the 1,4-dioxane (0.5 mL) was added to the system by syringe. The mixture was stirred at 150 8C for 24 h. When the reaction was complete, the resulting mixture was cooled to room temperature and filtered through a short silica-gel pad. Then, the mixture was concentrated in vacuo to give a residue, which was purified by preparative TLC to afford the corresponding product.
Scheme 2. Suzuki coupling of 3 q with phenylboronic acid.
Acknowledgements The authors are grateful to the National Natural Science Foundation of China (Grant Nos. 20906059 and 21272145), Shaanxi Innovative Team of Key Science and Technology (Grant No. 2013 KCT-17), the Fundamental Research Funds for the Central Universities (Grant Nos. GK201102005 and GK261001095), and Canada Research Chair (to C.J.L.) for providing financial support for this research. Keywords: amidation · C H activation · decarboxylation · homogeneous catalysis · synthetic methods [1] a) J. Yamaguchi, A. D. Yamaguchi, K. Itami, Angew. Chem. Int. Ed. 2012, 51, 8960 – 9009; Angew. Chem. 2012, 124, 9092 – 9142; b) D. Alberico, M. E. Scott, M. Lautens, Chem. Rev. 2007, 107, 174 – 238; c) C. Coperet, Chem. Rev. 2010, 110, 656 – 680; d) I. Mkhalid, J. Barnard, T. Marder, J. Murphy, J. Hartwig, Chem. Rev. 2010, 110, 890 – 931; e) T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147 – 1169; f) X. Chen, K. M. Engle, D.-H. Wang, J.-Q. Yu, Angew. Chem. Int. Ed. 2009, 48, 5094 – 5115; Angew. Chem. 2009, 121, 5196 – 5217; g) I. V. Seregin, V. Gevorgyan, Chem. Soc. Rev. 2007, 36, 1173 – 1193; h) J. C. Lewis, R. G. Bergman, J. A. Ellman, Acc. Chem. Res. 2008, 41, 1013 – 1025; i) M. M. Daz-Requejo, P. J. Prez, Chem.
Scheme 3. Proposed catalytic cycle. Chem. Eur. J. 2014, 20, 1 – 5
www.chemeurj.org
These are not the final page numbers! ÞÞ
3
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
Communication
[2] [3]
[4]
[5]
[6]
[7] [8] [9] [10]
[11] [12]
&
&
Rev. 2008, 108, 3379 – 3394; j) E. M. Beccalli, G. Broggini, M. Martinelli, S. Sottocornola, Chem. Rev. 2007, 107, 5318 – 5365; k) D. A. Colby, R. G. Bergman, J. A. Ellman, Chem. Rev. 2010, 110, 624 – 655; l) K. Godula, D. Sames, Science 2006, 312, 67 – 72; m) F. Kakiuchi, S. Murai, Acc. Chem. Res. 2002, 35, 826 – 834; n) V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev. 2002, 102, 1731 – 1770; o) C. Jia, T. Kitamura, Y. Fujiwara, Acc. Chem. Res. 2001, 34, 633 – 639. P. Duan, Y. Yang, R. Ben, Y. Yan, L. Dai, M. Hong, Y.-D. Wu, D. Wang, X. Zhang, J. Zhao, Chem. Sci. 2014, 5, 1574 – 1578. a) L. Ackermann, A. V. Lygin, Org. Lett. 2012, 14, 764 – 767; b) L. Ackermann, J. Pospech, K. Graczyk, K. Rauch, Org. Lett. 2012, 14, 930 – 933; c) G. Liu, Y. Shen, Z. Zhou, X. Lu, Angew. Chem. Int. Ed. 2013, 52, 6033 – 6037; Angew. Chem. 2013, 125, 6149 – 6153; d) J. R. Huckins, E. A. Bercot, O. R. Thiel, T.-L. Hwang, M. M. Bio, J. Am. Chem. Soc. 2013, 135, 14492 – 14495; e) N. Guimond, C. Gouliaras, K. Fagnou, J. Am. Chem. Soc. 2010, 132, 6908 – 6909; f) T. K. Hyster, T. Rovis, J. Am. Chem. Soc. 2010, 132, 10565 – 10569; g) R. M. Martin, R. G. Bergman, J. A. Ellman, J. Org. Chem. 2012, 77, 2501 – 2507; h) D. Zhao, Z. Shi, F. Glorius, Angew. Chem. Int. Ed. 2013, 52, 12426 – 12429; Angew. Chem. 2013, 125, 12652 – 12656. a) A. S. Tsai, M. E. Tauchert, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc. 2011, 133, 1248 – 1250; b) Y. Li, B.-J. Li, W.-H. Wang, W.-P. Huang, X.-S. Zhang, K. Chen, Z.-J. Shi, Angew. Chem. Int. Ed. 2011, 50, 2115 – 2119; Angew. Chem. 2011, 123, 2163 – 2167; c) M. E. Tauchert, C. D. Incarvito, A. L. Rheingold, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc. 2012, 134, 1482 – 1485; d) K. D. Hesp, R. G. Bergman, J. A. Ellman, Org. Lett. 2012, 14, 2304 – 2307; e) Y. Li, X.-S. Zhang, H. Li, W.-H. Wang, K. Chen, B.-J. Li, Z.-J. Shi, Chem. Sci. 2012, 3, 1634 – 1639; f) B. Zhou, Y. Yang, S. Lin, Y. Li, Adv. Synth. Catal. 2013, 355, 360 – 364; g) C. Zhu, W. Xie, J. R. Falck, Chem. Eur. J. 2011, 17, 12591 – 12595; h) J. Y. Kim, S. H. Park, J. Ryu, S. H. Cho, S. H. Kim, S. Chang, J. Am. Chem. Soc. 2012, 134, 9110 – 9113; i) J. Shi, B. Zhou, Y. Yang, Y. Li, Org. Biomol. Chem. 2012, 10, 8953 – 8955; j) J. Ryu, K. Shin, S. H. Park, J. Y. Kim, S. Chang, Angew. Chem. Int. Ed. 2012, 51, 9904 – 9908; Angew. Chem. 2012, 124, 10042 – 10046; k) J. Aydin, K. Szab, Org. Lett. 2008, 10, 2881 – 2884; l) J. Aydin, C. S. Conrad, K. J. Szab, Org. Lett. 2008, 10, 5175 – 5178; m) B. Qian, S. Guo, J. Shao, Q. Zhu, L. Yang, C. Xia, H. Huang, J. Am. Chem. Soc. 2010, 132, 3650 – 3651. a) A. Graul, J. Castaner, Drugs Future 1997, 22, 956 – 968; b) A. A. Patchett, J. Med. Chem. 1993, 36, 2051 – 2058; c) M. de Gasparo, S. Whitebread, Regul. Pept. 1995, 59, 303 – 311; d) V. S. Ananthanarayanan, S. Tetreault, A. Saint-Jean, J. Med. Chem. 1993, 36, 1324 – 1332. a) J. S. Carey, D. Laffan, C. Thomson, M. T. Williams, Org. Biomol. Chem. 2006, 4, 2337 – 2347; b) T. Cupido, J. Tulla-Puche, J. Spengler, F. Albericio, Curr. Opin. Drug Discovery Dev. 2007, 10, 768 – 783; c) M. A. Mintzer, E. E. Simanek, Chem. Rev. 2009, 109, 259 – 302; d) V. R. Pattabiraman, J. W. Bode, Nature 2011, 480, 471 – 479; e) J. M. Humphrey, A. R. Chamberlin, Chem. Rev. 1997, 97, 2243 – 2266. F. Xiao, C. Tang, G. J. Deng, Org. Lett. 2012, 14, 984 – 987. K. Muralirajan, K. Parthasarathy, C.-H. Cheng, Org. Lett. 2012, 14, 4262 – 4265. K. D. Hesp, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc. 2011, 133, 11430 – 11433. a) Y. Kuninobu, Y. Tokunaga, A. Kawata, K. Takai, J. Am. Chem. Soc. 2006, 128, 202 – 209; b) Y. Kuninobu, Y. Tokunaga, K. Takai, Chem. Lett. 2007, 36, 872 – 873; c) W. Hou, B. Zhou, Y. Yang, H. Feng, Y. Li, Org. Lett. 2013, 15, 1814 – 1817; d) B. Zhou, W. Hou, Y. Yang, Y. Li, Chem. Eur. J. 2013, 19, 4701 – 4706. S. De Sarkar, L. Ackermann, Chem. Eur. J. 2014, 20, 13932 – 13936. a) R. Shang, L. Liu, Sci. China Chem. 2011, 54, 1670 – 1687; b) S. Xiang, S. Cai, J. Zeng, X.-W. Liu, Org. Lett. 2011, 13, 4608 – 4611; c) S. Ranjit, Z. Duan, P. Zhang, X. Liu, Org. Lett. 2010, 12, 4134 – 4136; d) J. Hu, N. Zhao, B. Yang, G. Wang, L.-N. Guo, Y.-M. Liang, S.-D. Yang, Chem. Eur. J. 2011,
Chem. Eur. J. 2014, 20, 1 – 5
www.chemeurj.org
[13]
[14]
[15] [16]
[17]
[18]
[19]
17, 5516 – 5521; e) L. J. Goossen, G. J. Deng, L. M. Levy, Science 2006, 313, 662 – 664; f) L. J. Goossen, B. Zimmermann, T. Knauber, Angew. Chem. Int. Ed. 2008, 47, 7103 – 7106; Angew. Chem. 2008, 120, 7211 – 7214; g) L. J. Goossen, N. Rodrguez, C. Linder, J. Am. Chem. Soc. 2008, 130, 15248 – 15249; h) L. J. Goossen, N. Rodrguez, P. P. Lange, C. Linder, Angew. Chem. Int. Ed. 2010, 49, 1111 – 1114; Angew. Chem. 2010, 122, 1129 – 1132; i) L. J. Goossen, N. Rodrguez, B. Melzer, C. Linder, G. J. Deng, L. M. Levy, J. Am. Chem. Soc. 2007, 129, 4824 – 4833; j) Z. Y. Duan, S. Ranjit, P. F. Zhang, X. G. Liu, Chem. Eur. J. 2009, 15, 3666 – 3669. a) J. S. Dickstein, C. A. Mulrooney, E. M. O’Brien, B. J. Morgan, M. C. Kozlowski, Org. Lett. 2007, 9, 2441 – 2444; b) D. Nandi, Y.-M. Jhou, J.-Y. Lee, B.-C. Kuo, C.-Y. Liu, P.-W. Huang, H. M. Lee, J. Org. Chem. 2012, 77, 9384 – 9390; c) H. Zhao, Y. Wei, J. Xu, J. Kan, W. Su, M. Hong, J. Org. Chem. 2011, 76, 882 – 893; d) C. Li, B. Breit, J. Am. Chem. Soc. 2014, 136, 862 – 865; e) A. Kumar, M. Kumar, L. P. Gupta, M. K. Gupta, RSC Adv. 2014, 4, 9412 – 9415; f) H. Yang, H. Yan, P. Sun, Y. Zhu, L. Lu, D. Liu, G. Rong, J. Mao, Green Chem. 2013, 15, 976 – 981; g) Y. Zhang, S. Patel, N. Mainolfi, Chem. Sci. 2012, 3, 3196 – 3199; h) W. I. Dzik, P. P. Lange, L. J. Gooßen, Chem. Sci. 2012, 3, 2671 – 2678; i) X. Li, D. Zou, F. Leng, C. Sun, J. Li, Y. Wu, Y. Wu, Chem. Commun. 2013, 49, 312 – 314; j) H. Yang, P. Sun, Y. Zhu, H. Yan, L. Lu, X. Qu, T. Li, J. Mao, Chem. Commun. 2012, 48, 7847 – 7849; k) N. Wu, F. Song, L. Yan, J. Li, J. You, Chem. Eur. J. 2014, 20, 3408 – 3414; l) Z. Fu, S. Huang, W. Su, M. Hong, Org. Lett. 2010, 12, 4992 – 4995; m) A. Carrr, J.-D. Brion, S. Messaoudi, M. Alami, Adv. Synth. Catal. 2013, 355, 2044 – 2054. a) A. Maehara, H. Tsurugi, T. Satoh, M. Miura, Org. Lett. 2008, 10, 1159 – 1162; b) S. Mochida, K. Hirano, T. Satoh, M. Miura, Org. Lett. 2010, 12, 5776 – 5779; c) J. Cornella, M. Righi, I. Larrosa, Angew. Chem. Int. Ed. 2011, 50, 9429 – 9432; Angew. Chem. 2011, 123, 9601 – 9604; d) S. Mochida, K. Hirano, T. Satoh, M. Miura, J. Org. Chem. 2011, 76, 3024 – 3033; e) S. Bhadra, W. I. Dzik, L. J. Gooßen, Angew. Chem. Int. Ed. 2013, 52, 2959 – 2962; Angew. Chem. 2013, 125, 3031 – 3035. X.-Y. Shi, A. Renzetti, S. Kundu, C.-J. Li, Adv. Synth. Catal. 2014, 356, 723 – 728. a) L. J. Goossen, F. Manjolinho, B. A. Khan, N. Rodriguez, J. Org. Chem. 2009, 74, 2620 – 2623; b) G. Cahiez, A. Moyeux, O. Gager, M. Poizat, Adv. Synth. Catal. 2013, 355, 790 – 796. M. Kamata, T. Yamashita, T. Imaeda, T. Tanaka, J. Terauchi, M. Miyamoto, T. Ora, M. Tawada, S. Endo, S. Takekawa, A. Asami, N. Suzuki, Y. Nagisa, Y. Nakano, K. Watanabe, H. Ogino, K. Kato, K. Kato, Y. Ishihara, Bioorg. Med. Chem. 2011, 19, 5539 – 5552. a) X. Jia, J. Han, J. Org. Chem. 2014, 79, 4180 – 4185; b) K. Parthasarathy, A. R. Azcargorta, Y. Cheng, C. Bolm, Org. Lett. 2014, 16, 2538 – 2541; c) B. Liu, T. Zhou, B. Li, S. Xu, H. Song, B. Wang, Angew. Chem. Int. Ed. 2014, 53, 4191 – 4195; Angew. Chem. 2014, 126, 4275 – 4279; d) M.-Z. Lu, P. Lu, Y.-H. Xu, T.-P. Loh, Org. Lett. 2014, 16, 2614 – 2617; e) H.-W. Lam, K.-Y. Man, W.-W. Chan, Z. Zhou, W.-Y. Yu, Org. Biomol. Chem. 2014, 12, 4112 – 4116; f) T. Yang, T. Zhang, S. Yang, S. Chen, X. Li, Org. Biomol. Chem. 2014, 12, 4290 – 4294; g) T. Ryu, J. Min, W. Choi, W. H. Jeon, P. H. Lee, Org. Lett. 2014, 16, 2810 – 2813; h) N. Wang, R. Li, L. Li, S. Xu, H. Song, B. Wang, J. Org. Chem. 2014, 79, 5379 – 5385; i) K. Muralirajan, C.-H. Cheng, Adv. Synth. Catal. 2014, 356, 1571 – 1576; j) D. Zhao, F. Lied, F. Glorius, Chem. Sci. 2014, 5, 2869 – 2873; k) X.-Y. Shi, C.-J. Li, Adv. Synth. Catal. 2012, 354, 2933 – 2938. a) L. J. Goossen, N. Rodriguez, C. Linder, P. P. Lange, A. Fromm, ChemCatChem 2010, 2, 430 – 442; b) J. Cornella, C. Sanchez, D. Banawa, I. Larrosa, Chem. Commun. 2009, 7176 – 7178.
Received: November 9, 2014 Published online on && &&, 0000
4
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Communication
COMMUNICATION &C
H Activation
X.-Y. Shi,* K.-Y. Liu, J. Fan, X.-F. Dong, J.-F. Wei, C.-J. Li* Kill the director: The rhodium-catalyzed amidation of substituted benzoic acids with isocyanates via directed C H functionalization followed by decarboxylation to afford the corresponding N-aryl benzamides is demonstrated. The car-
Chem. Eur. J. 2014, 20, 1 – 5
boxylate serves as a unique, removable directing group. Notably, less common meta-substituted N-aryl benzamides are formed readily from more accessible para- or ortho-substituted groups by employing this strategy.
A Convenient Synthesis of N-Aryl Benzamides by Rhodium-Catalyzed ortho-Amidation and Decarboxylation of Benzoic Acids
5
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
These are not the final page numbers! ÞÞ
&& – &&
&
&
Communication
& C H Activation
A Convenient Synthesis of N-Aryl Benzamides by RhodiumCatalyzed ortho-Amidation and Decarboxylation of Benzoic Acids Xian-Ying Shi,*[a] Ke-Yan Liu,[a] Juan Fan,[a] Xue-Fen Dong,[a] Jun-Fa Wei,[a] and Chao-Jun Li*[b] alkenyl C H bond to isocyanates with subsequent cyclization, respectively.[10] Very recently, Ackermann and co-workers developed a versatile route to phthalimides by RuII-catalyzed C H activation of amides with isocyanates.[11] In all of these reports, the amide group was introduced ortho to the directing group, while the directing group remains in place “permanently”. Transition metal-catalyzed decarboxylative cross-coupling reactions have recently emerged as a new and important category of organic transformation that finds versatile applications in the construction of C C and C heteroatom bonds.[12] However, the new C C or C heteroatom bond is usually formed at the original position of the carboxylate group (Scheme 1 a) and
Abstract: The rhodium-catalyzed amidation of substituted benzoic acids with isocyanates by directed C H functionalization followed by decarboxylation to afford the corresponding N-aryl benzamides is demonstrated, in which the carboxylate serves as a unique, removable directing group. Notably, less common meta-substituted N-aryl benzamides are generated readily from more accessible paraor ortho-substituted groups by employing this strategy.
In recent decades, transition metal-catalyzed C H functionalization reactions have emerged as a powerful method in organic synthesis.[1] Chelation-assisted C H bond activation and subsequent addition to unsaturated molecules have offered many efficient syntheses in an atom-economic fashion.[2] The direct insertion of C H to unsaturated alkene and alkyne derivatives has been extensively investigated;[3] whereas analogous additions across polarized C N multiple bonds have seen considerably less progress. However, the installment of nitrogen-based functional groups into molecules through the direct addition of C H bonds to unsaturated C N multiple bonds represents a worthwhile pursuit with profound synthetic potentials.[4] In particular, the direct insertion of C H bonds into isocyanates is highly desirable since it can effectively provide synthetically valuable amide moieties,[5] which not only represent an important structural motif present in many natural products, polymers, pharmaceuticals, and biological systems,[6] but also are of great importance as intermediates for the preparation of various useful compounds.[7] In this context, Cheng and co-workers illustrated an efficient RuII-catalyzed amidation of 2-arylpyridines with isocyanates by C H bond activation.[8] A RhIII-catalyzed protocol for amidation of anilide and enamide C H bonds with isocyanates was developed by Ellman and co-workers.[9] The groups of Takai and Li reported ReII and RhIII-catalyzed addition of an
Scheme 1. Decarboxylative C C cross-coupling reactions.
there are only few reports using carboxylic acids as a traceless directing group (Scheme 1 b).[12b, 13, 14] In the course of our study on the cascade cyclization of o-toluic acid with phenyl isocyanate,[15] we unexpectedly observed that the acid-free 3-methylN-phenylbenzamide was generated under rhodium catalysis (Scheme 1 c). This finding indicates that the reaction involved a carboxyl-directed ortho-amidation of o-toluic acid via C H functionalization followed by decarboxylation. Namely, the carboxy group acted as a removable ortho-directing group. We reasoned that, by employing this strategy, N-aryl benzamides with more difficult substitutions could be obtained readily
[a] Dr. X.-Y. Shi, K.-Y. Liu, J. Fan, X.-F. Dong, Prof. Dr. J.-F. Wei Key Laboratory of Applied Surface and Colloid Chemistry (Ministry of Education), Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710062 (P. R. China) E-mail: [email protected] [b] Prof. Dr. C.-J. Li Department of Chemistry, McGill University Montreal, QC, H3 A 0B8 (Canada) E-mail: [email protected] Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201406031. Chem. Eur. J. 2014, 20, 1 – 5
These are not the final page numbers! ÞÞ
1
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
Communication from other substituted benzoic acids, which are conveniently more accessible. Herein, we present the convenient synthesis of N-aryl benzamides by rhodium-catalyzed ortho-amidation and decarboxylation of benzoic acids. To understand the nature of this reaction and to optimize the reaction conditions, different solvents were first examined, given the importance of solvent effects in catalytic reactions (Table 1, entries 1–9). Solvent screenings revealed that dioxane provided a slightly higher yield than THF, chlorobenzene, tolu-
K2HPO4 and Cu2O was used in the reaction system (Table 1, entry 20). Having established the optimized reaction conditions, the substrate scope was examined with respect to the substituted benzoic acids (Table 2). No desired product was isolated using 2-nitrobenzoic acid, bearing a strong electron-withdrawing
Table 2. Substrate scope for the C H functionalization–decarboxylation Reaction.[a]
Table 1. Selected results for optimizing reaction conditions.[a]
Entry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Additive (equiv)
Solvent
Yield [%][b]
K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(1.0) K2HPO4(2.0) — Na2HPO4(2.0) KH2PO4(2.0) NaH2PO4(2.0) K3PO4(2.0) K2CO3(2.0) Na2CO3(2.0) Li2CO3(21.0) Ag2CO3(2.0) K2HPO4 (2.0)/Cu2O (0.15)
THF C6H5Cl toluene o-xylene dioxane DCE DMF CH3CN t-BuOH dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane dioxane
13 11 10 11 23 ND[c] ND ND ND 48 ND ND trace ND 12 25 40 29 14 65
[a] Reactions were carried out with o-toluic acid (0.1 mmol), phenylisocyanate (0.2 mmol), [{Cp*RhCl2}2] (5 mol %), additives, and solvent (0.5 mL) at 150 8C for 24 h, under argon in pressure tubes; [b] determined by 1H NMR spectroscopy of the crude reaction mixture using mesitylene as internal standard; [c] ND = not detected.
[a] Reactions were carried out with acids (0.2 mmol), isocyanates (0.4 mmol), [{Cp*RhCl2}2] (5 mol %), dioxane (0.5 mL), K2HPO4 (2.0 equiv), Cu2O (0.15 equiv), 150 8C, 24 h. Yield of isolated product was reported.
ene, or o-xylene, and no target product was detected when dichloroethane (DCE), DMF, acetonitrile, or tert-butanol were used as solvent. The moderate yield of 3 a could be enhanced to 48 % by increasing the amount of K2HPO4 to 2.0 equivalents. No desired product was formed in the absence of K2HPO4 (Table 1, entry 11), which suggested that the choice of salt is crucial for the success of the present catalytic reaction. Therefore, a series of salts was also examined for the reaction. Disappointingly, when other alkali phosphates such as Na2HPO4, KH2PO4, NaH2PO4, and K3PO4 were employed, either no desired product or only trace amounts thereof was formed (Table 1, entries 12–15). The use of carbonates also provided the desired product with decreased yield compared to K2HPO4 (Table 1, entries 16–19). Given that Cu2O is known to promote the decarboxylation,[13i, 16] different amounts of Cu2O were introduced to optimize the formation of this product. Finally, the yield of the product was further improved to 65 % when a mixture of &
&
Chem. Eur. J. 2014, 20, 1 – 5
www.chemeurj.org
group, which suggests that the parent carboxy group and the additional electron-withdrawing group render the aryl ring highly electron-deficient and retard the attacking of electrophilic rhodium. The location of substituents on the parent benzoic acid has a strong influence on the product yield. For example, o-methoxybenzoic acid afforded only 30 % yield of the product, which can be attributed to deactivation resulting from the coordination between an electron-rich heteroatom and rhodium. Compared with ortho-substituted benzoic acids, those bearing substituents at the para position were readily converted into the corresponding products in higher yields (Table 2; 3 a vs. 3 d, 3 b vs. 3 e, 3 c vs. 3 f). Meta-substituted benzoic acids also reacted smoothly to afford the corresponding products in high yields and generated two regioisomers (Table 2; 3 h and 3 h’), due to the two possible C H bond activation sites at C2 and C6. The amide formation occurred selectively para to the sub2
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Communication stituent, which illustrated that the reaction was mainly under steric control. This transformation tolerated dual substitution and 2,4-dimethylbenzoic acid gave the highest yield of the corresponding product (Table 2; 3 i–l). To further explore the substrate scope and limitations of this process, the reactions between 2,4-dimethylbenzoic acid and various isocyanates were tested (Table 2). 3-methyl, 4-methyl, and 3,5-dimethyl phenyl isocyanates underwent C H activation and a decarboxylation reaction effectively with 2,4-dimethylbenzoic acid, producing the corresponding products in 74 %, 80 %, and 77 % yields, respectively (3 m, 3 n, 3 p). In the presence of electron-withdrawing groups such as Cl and Br, the desired products were also obtained, although the yields were somewhat decreased (3 o, 3 q, 3 r). Particularly noteworthy was that halo groups (Cl, Br) on the aromatic ring of isocyanate remained intact in the product, which provides the possibility for further useful transformations through common cross-coupling strategies. Thus, as a proof-of-concept, using 3 q as the reactant, a further transformation of the product by employing the Suzuki reaction afforded the product 4 q in 38 % yield (Scheme 2).[17] Based on known rhodium-catalyzed directing-group-assisted C H bond activation reactions[18] and metal-mediated decarboxylation reactions,[19] a tentative mechanism to rationalize this reaction is depicted in Scheme 3. Dissociation of the dimer precatalyst [{Cp*RhCl2}2] provides the coordinatively unsaturated monomer. With the help of K2HPO4, coordination of the
rhodium species to the carboxylic oxygen atom and subsequent ortho C H activation affords a five-membered rhodacyclic intermediate B, releasing one equivalent of proton at the same time. Then, isocyanate is coordinated to B at Rh to form C, followed by the insertion of the isocyanate into the Rh C bond of C to generate the seven-membered rhodium alkoxide D. Protonation of D by HCl affords the intermediate E and regenerates the active RhIII species for the next cycle. Finally, decarboxylation of E followed by protonation provides the final product. In summary, we have succeeded in preparing a series of Naryl benzamides from readily available benzoic acids and isocyanates through regiospecific amidation of aromatic ortho-C H groups with concomitant decarboxylation. In these reactions, the carboxy function effectively serves as a removable directing group. Notably, less common meta-substituted N-aryl benzamides can arise readily from more accessible para- or orthosubstituted groups by employing this strategy.
Experimental Section An oven-dried reaction vessel was charged with [{Cp*RhCl2}2] (6.2 mg, 5 mol %, 0.01 mmol), acid 1 (0.2 mmol), isocyanate 2 (0.4 mmol), K2HPO4 (69.6 mg, 0.4 mmol), Cu2O (4.4 mg, 0.06 mmol). After the tube was evacuated and purged with argon three times, the 1,4-dioxane (0.5 mL) was added to the system by syringe. The mixture was stirred at 150 8C for 24 h. When the reaction was complete, the resulting mixture was cooled to room temperature and filtered through a short silica-gel pad. Then, the mixture was concentrated in vacuo to give a residue, which was purified by preparative TLC to afford the corresponding product.
Scheme 2. Suzuki coupling of 3 q with phenylboronic acid.
Acknowledgements The authors are grateful to the National Natural Science Foundation of China (Grant Nos. 20906059 and 21272145), Shaanxi Innovative Team of Key Science and Technology (Grant No. 2013 KCT-17), the Fundamental Research Funds for the Central Universities (Grant Nos. GK201102005 and GK261001095), and Canada Research Chair (to C.J.L.) for providing financial support for this research. Keywords: amidation · C H activation · decarboxylation · homogeneous catalysis · synthetic methods [1] a) J. Yamaguchi, A. D. Yamaguchi, K. Itami, Angew. Chem. Int. Ed. 2012, 51, 8960 – 9009; Angew. Chem. 2012, 124, 9092 – 9142; b) D. Alberico, M. E. Scott, M. Lautens, Chem. Rev. 2007, 107, 174 – 238; c) C. Coperet, Chem. Rev. 2010, 110, 656 – 680; d) I. Mkhalid, J. Barnard, T. Marder, J. Murphy, J. Hartwig, Chem. Rev. 2010, 110, 890 – 931; e) T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147 – 1169; f) X. Chen, K. M. Engle, D.-H. Wang, J.-Q. Yu, Angew. Chem. Int. Ed. 2009, 48, 5094 – 5115; Angew. Chem. 2009, 121, 5196 – 5217; g) I. V. Seregin, V. Gevorgyan, Chem. Soc. Rev. 2007, 36, 1173 – 1193; h) J. C. Lewis, R. G. Bergman, J. A. Ellman, Acc. Chem. Res. 2008, 41, 1013 – 1025; i) M. M. Daz-Requejo, P. J. Prez, Chem.
Scheme 3. Proposed catalytic cycle. Chem. Eur. J. 2014, 20, 1 – 5
www.chemeurj.org
These are not the final page numbers! ÞÞ
3
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
Communication
[2] [3]
[4]
[5]
[6]
[7] [8] [9] [10]
[11] [12]
&
&
Rev. 2008, 108, 3379 – 3394; j) E. M. Beccalli, G. Broggini, M. Martinelli, S. Sottocornola, Chem. Rev. 2007, 107, 5318 – 5365; k) D. A. Colby, R. G. Bergman, J. A. Ellman, Chem. Rev. 2010, 110, 624 – 655; l) K. Godula, D. Sames, Science 2006, 312, 67 – 72; m) F. Kakiuchi, S. Murai, Acc. Chem. Res. 2002, 35, 826 – 834; n) V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev. 2002, 102, 1731 – 1770; o) C. Jia, T. Kitamura, Y. Fujiwara, Acc. Chem. Res. 2001, 34, 633 – 639. P. Duan, Y. Yang, R. Ben, Y. Yan, L. Dai, M. Hong, Y.-D. Wu, D. Wang, X. Zhang, J. Zhao, Chem. Sci. 2014, 5, 1574 – 1578. a) L. Ackermann, A. V. Lygin, Org. Lett. 2012, 14, 764 – 767; b) L. Ackermann, J. Pospech, K. Graczyk, K. Rauch, Org. Lett. 2012, 14, 930 – 933; c) G. Liu, Y. Shen, Z. Zhou, X. Lu, Angew. Chem. Int. Ed. 2013, 52, 6033 – 6037; Angew. Chem. 2013, 125, 6149 – 6153; d) J. R. Huckins, E. A. Bercot, O. R. Thiel, T.-L. Hwang, M. M. Bio, J. Am. Chem. Soc. 2013, 135, 14492 – 14495; e) N. Guimond, C. Gouliaras, K. Fagnou, J. Am. Chem. Soc. 2010, 132, 6908 – 6909; f) T. K. Hyster, T. Rovis, J. Am. Chem. Soc. 2010, 132, 10565 – 10569; g) R. M. Martin, R. G. Bergman, J. A. Ellman, J. Org. Chem. 2012, 77, 2501 – 2507; h) D. Zhao, Z. Shi, F. Glorius, Angew. Chem. Int. Ed. 2013, 52, 12426 – 12429; Angew. Chem. 2013, 125, 12652 – 12656. a) A. S. Tsai, M. E. Tauchert, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc. 2011, 133, 1248 – 1250; b) Y. Li, B.-J. Li, W.-H. Wang, W.-P. Huang, X.-S. Zhang, K. Chen, Z.-J. Shi, Angew. Chem. Int. Ed. 2011, 50, 2115 – 2119; Angew. Chem. 2011, 123, 2163 – 2167; c) M. E. Tauchert, C. D. Incarvito, A. L. Rheingold, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc. 2012, 134, 1482 – 1485; d) K. D. Hesp, R. G. Bergman, J. A. Ellman, Org. Lett. 2012, 14, 2304 – 2307; e) Y. Li, X.-S. Zhang, H. Li, W.-H. Wang, K. Chen, B.-J. Li, Z.-J. Shi, Chem. Sci. 2012, 3, 1634 – 1639; f) B. Zhou, Y. Yang, S. Lin, Y. Li, Adv. Synth. Catal. 2013, 355, 360 – 364; g) C. Zhu, W. Xie, J. R. Falck, Chem. Eur. J. 2011, 17, 12591 – 12595; h) J. Y. Kim, S. H. Park, J. Ryu, S. H. Cho, S. H. Kim, S. Chang, J. Am. Chem. Soc. 2012, 134, 9110 – 9113; i) J. Shi, B. Zhou, Y. Yang, Y. Li, Org. Biomol. Chem. 2012, 10, 8953 – 8955; j) J. Ryu, K. Shin, S. H. Park, J. Y. Kim, S. Chang, Angew. Chem. Int. Ed. 2012, 51, 9904 – 9908; Angew. Chem. 2012, 124, 10042 – 10046; k) J. Aydin, K. Szab, Org. Lett. 2008, 10, 2881 – 2884; l) J. Aydin, C. S. Conrad, K. J. Szab, Org. Lett. 2008, 10, 5175 – 5178; m) B. Qian, S. Guo, J. Shao, Q. Zhu, L. Yang, C. Xia, H. Huang, J. Am. Chem. Soc. 2010, 132, 3650 – 3651. a) A. Graul, J. Castaner, Drugs Future 1997, 22, 956 – 968; b) A. A. Patchett, J. Med. Chem. 1993, 36, 2051 – 2058; c) M. de Gasparo, S. Whitebread, Regul. Pept. 1995, 59, 303 – 311; d) V. S. Ananthanarayanan, S. Tetreault, A. Saint-Jean, J. Med. Chem. 1993, 36, 1324 – 1332. a) J. S. Carey, D. Laffan, C. Thomson, M. T. Williams, Org. Biomol. Chem. 2006, 4, 2337 – 2347; b) T. Cupido, J. Tulla-Puche, J. Spengler, F. Albericio, Curr. Opin. Drug Discovery Dev. 2007, 10, 768 – 783; c) M. A. Mintzer, E. E. Simanek, Chem. Rev. 2009, 109, 259 – 302; d) V. R. Pattabiraman, J. W. Bode, Nature 2011, 480, 471 – 479; e) J. M. Humphrey, A. R. Chamberlin, Chem. Rev. 1997, 97, 2243 – 2266. F. Xiao, C. Tang, G. J. Deng, Org. Lett. 2012, 14, 984 – 987. K. Muralirajan, K. Parthasarathy, C.-H. Cheng, Org. Lett. 2012, 14, 4262 – 4265. K. D. Hesp, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc. 2011, 133, 11430 – 11433. a) Y. Kuninobu, Y. Tokunaga, A. Kawata, K. Takai, J. Am. Chem. Soc. 2006, 128, 202 – 209; b) Y. Kuninobu, Y. Tokunaga, K. Takai, Chem. Lett. 2007, 36, 872 – 873; c) W. Hou, B. Zhou, Y. Yang, H. Feng, Y. Li, Org. Lett. 2013, 15, 1814 – 1817; d) B. Zhou, W. Hou, Y. Yang, Y. Li, Chem. Eur. J. 2013, 19, 4701 – 4706. S. De Sarkar, L. Ackermann, Chem. Eur. J. 2014, 20, 13932 – 13936. a) R. Shang, L. Liu, Sci. China Chem. 2011, 54, 1670 – 1687; b) S. Xiang, S. Cai, J. Zeng, X.-W. Liu, Org. Lett. 2011, 13, 4608 – 4611; c) S. Ranjit, Z. Duan, P. Zhang, X. Liu, Org. Lett. 2010, 12, 4134 – 4136; d) J. Hu, N. Zhao, B. Yang, G. Wang, L.-N. Guo, Y.-M. Liang, S.-D. Yang, Chem. Eur. J. 2011,
Chem. Eur. J. 2014, 20, 1 – 5
www.chemeurj.org
[13]
[14]
[15] [16]
[17]
[18]
[19]
17, 5516 – 5521; e) L. J. Goossen, G. J. Deng, L. M. Levy, Science 2006, 313, 662 – 664; f) L. J. Goossen, B. Zimmermann, T. Knauber, Angew. Chem. Int. Ed. 2008, 47, 7103 – 7106; Angew. Chem. 2008, 120, 7211 – 7214; g) L. J. Goossen, N. Rodrguez, C. Linder, J. Am. Chem. Soc. 2008, 130, 15248 – 15249; h) L. J. Goossen, N. Rodrguez, P. P. Lange, C. Linder, Angew. Chem. Int. Ed. 2010, 49, 1111 – 1114; Angew. Chem. 2010, 122, 1129 – 1132; i) L. J. Goossen, N. Rodrguez, B. Melzer, C. Linder, G. J. Deng, L. M. Levy, J. Am. Chem. Soc. 2007, 129, 4824 – 4833; j) Z. Y. Duan, S. Ranjit, P. F. Zhang, X. G. Liu, Chem. Eur. J. 2009, 15, 3666 – 3669. a) J. S. Dickstein, C. A. Mulrooney, E. M. O’Brien, B. J. Morgan, M. C. Kozlowski, Org. Lett. 2007, 9, 2441 – 2444; b) D. Nandi, Y.-M. Jhou, J.-Y. Lee, B.-C. Kuo, C.-Y. Liu, P.-W. Huang, H. M. Lee, J. Org. Chem. 2012, 77, 9384 – 9390; c) H. Zhao, Y. Wei, J. Xu, J. Kan, W. Su, M. Hong, J. Org. Chem. 2011, 76, 882 – 893; d) C. Li, B. Breit, J. Am. Chem. Soc. 2014, 136, 862 – 865; e) A. Kumar, M. Kumar, L. P. Gupta, M. K. Gupta, RSC Adv. 2014, 4, 9412 – 9415; f) H. Yang, H. Yan, P. Sun, Y. Zhu, L. Lu, D. Liu, G. Rong, J. Mao, Green Chem. 2013, 15, 976 – 981; g) Y. Zhang, S. Patel, N. Mainolfi, Chem. Sci. 2012, 3, 3196 – 3199; h) W. I. Dzik, P. P. Lange, L. J. Gooßen, Chem. Sci. 2012, 3, 2671 – 2678; i) X. Li, D. Zou, F. Leng, C. Sun, J. Li, Y. Wu, Y. Wu, Chem. Commun. 2013, 49, 312 – 314; j) H. Yang, P. Sun, Y. Zhu, H. Yan, L. Lu, X. Qu, T. Li, J. Mao, Chem. Commun. 2012, 48, 7847 – 7849; k) N. Wu, F. Song, L. Yan, J. Li, J. You, Chem. Eur. J. 2014, 20, 3408 – 3414; l) Z. Fu, S. Huang, W. Su, M. Hong, Org. Lett. 2010, 12, 4992 – 4995; m) A. Carrr, J.-D. Brion, S. Messaoudi, M. Alami, Adv. Synth. Catal. 2013, 355, 2044 – 2054. a) A. Maehara, H. Tsurugi, T. Satoh, M. Miura, Org. Lett. 2008, 10, 1159 – 1162; b) S. Mochida, K. Hirano, T. Satoh, M. Miura, Org. Lett. 2010, 12, 5776 – 5779; c) J. Cornella, M. Righi, I. Larrosa, Angew. Chem. Int. Ed. 2011, 50, 9429 – 9432; Angew. Chem. 2011, 123, 9601 – 9604; d) S. Mochida, K. Hirano, T. Satoh, M. Miura, J. Org. Chem. 2011, 76, 3024 – 3033; e) S. Bhadra, W. I. Dzik, L. J. Gooßen, Angew. Chem. Int. Ed. 2013, 52, 2959 – 2962; Angew. Chem. 2013, 125, 3031 – 3035. X.-Y. Shi, A. Renzetti, S. Kundu, C.-J. Li, Adv. Synth. Catal. 2014, 356, 723 – 728. a) L. J. Goossen, F. Manjolinho, B. A. Khan, N. Rodriguez, J. Org. Chem. 2009, 74, 2620 – 2623; b) G. Cahiez, A. Moyeux, O. Gager, M. Poizat, Adv. Synth. Catal. 2013, 355, 790 – 796. M. Kamata, T. Yamashita, T. Imaeda, T. Tanaka, J. Terauchi, M. Miyamoto, T. Ora, M. Tawada, S. Endo, S. Takekawa, A. Asami, N. Suzuki, Y. Nagisa, Y. Nakano, K. Watanabe, H. Ogino, K. Kato, K. Kato, Y. Ishihara, Bioorg. Med. Chem. 2011, 19, 5539 – 5552. a) X. Jia, J. Han, J. Org. Chem. 2014, 79, 4180 – 4185; b) K. Parthasarathy, A. R. Azcargorta, Y. Cheng, C. Bolm, Org. Lett. 2014, 16, 2538 – 2541; c) B. Liu, T. Zhou, B. Li, S. Xu, H. Song, B. Wang, Angew. Chem. Int. Ed. 2014, 53, 4191 – 4195; Angew. Chem. 2014, 126, 4275 – 4279; d) M.-Z. Lu, P. Lu, Y.-H. Xu, T.-P. Loh, Org. Lett. 2014, 16, 2614 – 2617; e) H.-W. Lam, K.-Y. Man, W.-W. Chan, Z. Zhou, W.-Y. Yu, Org. Biomol. Chem. 2014, 12, 4112 – 4116; f) T. Yang, T. Zhang, S. Yang, S. Chen, X. Li, Org. Biomol. Chem. 2014, 12, 4290 – 4294; g) T. Ryu, J. Min, W. Choi, W. H. Jeon, P. H. Lee, Org. Lett. 2014, 16, 2810 – 2813; h) N. Wang, R. Li, L. Li, S. Xu, H. Song, B. Wang, J. Org. Chem. 2014, 79, 5379 – 5385; i) K. Muralirajan, C.-H. Cheng, Adv. Synth. Catal. 2014, 356, 1571 – 1576; j) D. Zhao, F. Lied, F. Glorius, Chem. Sci. 2014, 5, 2869 – 2873; k) X.-Y. Shi, C.-J. Li, Adv. Synth. Catal. 2012, 354, 2933 – 2938. a) L. J. Goossen, N. Rodriguez, C. Linder, P. P. Lange, A. Fromm, ChemCatChem 2010, 2, 430 – 442; b) J. Cornella, C. Sanchez, D. Banawa, I. Larrosa, Chem. Commun. 2009, 7176 – 7178.
Received: November 9, 2014 Published online on && &&, 0000
4
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Communication
COMMUNICATION &C
H Activation
X.-Y. Shi,* K.-Y. Liu, J. Fan, X.-F. Dong, J.-F. Wei, C.-J. Li* Kill the director: The rhodium-catalyzed amidation of substituted benzoic acids with isocyanates via directed C H functionalization followed by decarboxylation to afford the corresponding N-aryl benzamides is demonstrated. The car-
Chem. Eur. J. 2014, 20, 1 – 5
boxylate serves as a unique, removable directing group. Notably, less common meta-substituted N-aryl benzamides are formed readily from more accessible para- or ortho-substituted groups by employing this strategy.
A Convenient Synthesis of N-Aryl Benzamides by Rhodium-Catalyzed ortho-Amidation and Decarboxylation of Benzoic Acids
5
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
These are not the final page numbers! ÞÞ
&& – &&
&
&
