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A vinylic Rosenmund-von Braun reaction: practical synthesis of acrylonitriles Alexandre Pradal and Gwilherm Evano*a
ChemComm Accepted Manuscript
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An efficient system based on acetone cyanohydrin and catalytic amounts of copper(I) iodide and 1,10-phenanthroline is reported for the cyanation of alkenyl iodides. A wide range of polysubstituted acrylonitriles could be obtained in fair to good yields and with complete retention of the geometry of the double bond. This extension of the Rosenmund-von Braun reaction also enabled a straightforward formal synthesis of the naturally occurring acrylonitrile alliarinoside. In addition to being versatile intermediates and building blocks for chemical synthesis, conjugated nitriles – frequently named acrylonitriles – are commonly found in natural products including hemi-phorboxazole A 1,1 simmondsin 2,2 calyculin A 23 (an inhibitor of protein phosphatases 1 and 2a), and the whole family of cyanoethylene glucosides natural products such as 4-6 (Figure 1).4 They are also at the core structure of various biologically active molecules, the most representative examples being the well-known tyrphostins family of tyrosine phosphorylation inhibitors 7.5 Selected examples of biologically relevant alkenyl nitriles6 also include trilostane 8,7 commercialized under the brand name Modrenal® and used for the treatment of Cushing’s disease and breast cancer, the nonnucleoside reverse transcriptase inhibitor rilpivirin 9,8 one of the most potent anti-HIV agents, or entacapone 10,9 whose use in combination with levodopa and carbidopa has been shown to improve the treatment of the symptoms of the Parkinson’s disease. Standard methods for the synthesis of alkenyl nitriles, mostly based on classical Wittig,10 Horner-Wadsworth-Emmons,11 and Peterson olefinations,12 suffer from severe limitations such as poor substrate scope, limited efficiency for the synthesis of polysubstituted acrylonitriles and/or poor E/Z selectivity. Although generally quite efficient, similar shortcomings are however found with other routes to conjugated nitriles based on dehydration of acrylamides or conjugated oximes,13 Heck reaction,14 cross-metathesis,15 carbocyanation of alkynes16 or direct allylic cyanation.17,18 An interesting alternative is based on the metal-catalyzed cyanation of alkenyl halides which, provided that the configuration of the double bond is fully retained during the cross-coupling and that no isomerization of the sensitive conjugated nitrile occurs, offers one of the most efficient routes to acrylonitriles. While several catalytic systems based on nickel,19 cobalt20 and palladium21 have been reported for this transformation over the years, most of them still
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Figure 1 Acrylonitrile-containing natural and/or biologically active molecules.
Chem. Commun., 2014, 00, 1-3 | 1
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display poor substrate scope (i.e. limitation to the synthesis of cinnamonitriles, poor yields starting from alkenyl iodides…), require harsh conditions and/or highly toxic reagents or rely on the use of expensive metal complexes and ligands. Based on these limitations, the use of a copper-based catalytic system that would enable expanding the Rosenmund-von Braun cyanation of aryl halides22,23 to the use of alkenyl halides seems an attractive option that has been for some reason rather underestimated.24 Motivated by the potential of such a reaction and based on our experience in copper catalysis,25,26 we decided to study the feasibility of a vinylic Rosenmund-von Braun reaction. We report in this manuscript an efficient system enabling the copper-catalyzed cyanation of a wide range of alkenyl halides with good efficiency and with complete retention of the double bond geometry. To evaluate the feasibility of this vinylic Rosenmund-von Braun reaction, the cyanation of (E)-p-methoxy--iodostyrene 11a was chosen as a test transformation. Different standard sources of cyanide were briefly evaluated for this reaction using a catalytic system inspired from the one reported by Taillefer in the aromatic series.23b As shown in Scheme 1, potassium hexacyanoferrate(II), K4[Fe(CN)6], an attractive non-toxic cyanation reagent, and sodium cyanide did not allow for a full conversion of 11a and only gave the cyanation product 12a in poor yields. Switching to potassium cyanide was found to be a lot more efficient since full conversion could be obtained with this reagent as well as a reasonable yield (80%) of the desired acrylonitrile 12a. A combination of acetone cyanohydrin 27 and tributylamine was found to be equally efficient and, due to its lower toxicity compared to potassium cyanide, was therefore selected as the cyanation reagent.
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ChemComm further derivatization. Moreover, a complete retention of the double bond geometry was observed in all cases since both E and Z starting iodoalkenes 11a-f and 11g-j could be transformed to the corresponding conjugated nitriles without isomerization, and even the corresponding Z-cinnamonitriles 12g-j could be obtained in good yields and high diastereoisomeric ratio. As a note, reacting the brominated analogue of 11a under the exact same reaction conditions failed to provide the corresponding conjugated nitrile 12a and attempts at using additional potassium iodide to perform an in situ vinylic Finkelstein reaction prior to the cyanation failed.
Scheme 1 Selection of the cyanation reagent (Yields and conversions determined by 1H NMR using diphenylmethane as internal standard)
Having demonstrated the possibility of expanding the Rosenmund-von Braun reaction in the vinylic series based on the use of a simple and readily available catalytic system, we moved to the assessment of the substrate scope of this transformation. As shown in Figure 2, this copper-catalyzed cyanation enabled the synthesis of a collection of diversely substituted alkenyl nitriles 12 from the corresponding readily available iodoalkenes 11. As evidenced by these results, a wide range of -iodo-styrene derivatives 11a-j could be readily transformed to the corresponding cinnamonitriles 12a-j that could be isolated in fair to good yields, regardless their steric and electronic properties. Electron-withdrawing and -donating groups were indeed shown to have little influence on the outcome of the reaction and, interestingly, a total chemoselectivity was observed starting from (E)-p-bromo--iodostyrene 11d which gave the corresponding acrylonitrile 12d without competitive cyanation of the aromatic bromide, therefore providing an excellent starting point for
2 | Chem. Commun., 2014, 00, 1-3
Figure 2 Copper-catalyzed cyanation of alkenyl iodides: scope and limitations (* reaction performed on a 5 mmol scale).
Importantly, the reaction is not limited to the small scale used for the scope and limitation studies and could be easily performed on a 5 mmol scale with similar efficiency, the low price of both the copper catalyst and the ligand being in addition an important beneficial point for the scale up of this reaction. Furthermore, the reaction could be efficiently extended to the synthesis of -alkyl-substituted acrylonitriles as shown with the preparation of 12k-p. To our delight, both E and Z -substituted iodoalkenes 11k,l and 11m,n were readily transformed to the corresponding cyanated products 12k,l and 12m,n in good yields and with complete retention of the geometry of the double bond. Even more interestingly, ,-disubstituted acylonitriles could also be easily
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ChemComm obtained, as demonstrated with the synthesis of 12o and 12p that could be obtained in 79 and 74% yield, respectively. We finally found that substitution close to the reacting center was equally well tolerated, as shown with the copper-catalyzed cyanation of 11r under standard conditions giving -substituted acrylonitrile 12r in 66% yield. The reaction was however shown to proceed less efficiently in the absence of a substituent in the -position, the corresponding acrylonitriles such as 12q being much less stable and more susceptible to undergo various side-reactions such as conjugated addition, which probably accounts for the lower efficiency of the copper-catalyzed cyanation involving such substrates. Finally, it ought to be mentioned that a number of substituents are well tolerated in the reaction, such as silyl ethers, ethers, acetals or benzylic positions. The possibility of performing a double cyanation was then briefly evaluated starting from substrate 13 possessing two vinyl iodides (Scheme 2). Under the standard conditions, the two vinyl iodides in 13 could be readily cyanated, providing bis-acrylonitrile 14, which could be isolated in reasonable yield (50%) provided that the reaction was run for 42 hours.
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Scheme 2 Copper-catalyzed double cyanation of a bis-vinyl iodide
We finally wanted to further test our procedure and evaluate its efficiency for the synthesis of more complex and sensitive acrylonitriles. With this goal in mind, we chose alliarinoside 4, a naturally occurring acrylonitrile,4d as a target and decided to check whether the copper-catalyzed cyanation of the corresponding iodoalkene could provide a valuable and synthetically useful route to this natural product. Z-Vinyl iodide 17 was therefore prepared by a Königs-Knorr glucosylation of readily available (Z)-3-iodoprop-2-en1-ol 16 with commercially available peracetyl -D-glucopyranosyl bromide 15 as shown in Scheme 3. Upon reaction with acetone cyanohydrin and tributylamine in the presence of 10 mol% copper(I) iodide and 20 mol% of 1,10-phenanthroline in DMF for 16h, we were pleased to isolate peracetyl-alliarinoside 18, a precursor of alliarinoside 4,4d in 59% yield on a 0.8 g scale and as a single Zisomer, therefore demonstrating the efficiency of the copper-catalyzed vinylic Rosenmund-von Braun reaction. Indeed, compared to the previously reported route to alliarinoside 4 in which the conjugated nitrile was installed from the corresponding aldehyde – itself obtained by ozonolysis of peracetyl-O-allyl--D-glucose – by the means of a Horner-Wadsworth-Emmons olefination yielding the desired Zacrylonitrile and its E-isomer in a 65:35 ratio,4d the use of a coppercatalyzed cyanation allows for a selective synthesis of alliarinoside 4 in addition to reducing the number of steps required for its preparation.
Scheme 3 Application of the copper-catalyzed cyanation to the formal synthesis of alliarinoside
Notes and references a
Laboratoire de Chimie Organique, Service de Chimie et PhysicoChimie Organiques, Université Libre de Bruxelles, Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium. Fax: +32 2 650 27 98; Tel: +32 2 650 30 57; E-mail: [email protected]. † The authors thank the Université Libre de Bruxelles and the FNRS (Incentive Grant for Scientific Research n° F.4530.13) for support. Electronic Supplementary Information (ESI) available: Experimental procedures, characterization, copies of 1H and 13C NMR spectra for all new compounds. See DOI: 10.1039/c000000x/ 1 2 3 4
Conclusions In conclusion, we have developed an efficient copper-catalyzed cyanation of alkenyl iodides which provides a straightforward, practical and robust entry to conjugated nitriles. This extension of the Rosenmund-von Braun reaction in the vinylic series, which relies on the use of acetone cyanohydrin as the cyanation reagent and on a
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M. Beller, Synlett, 2007, 555. (f) T. Schareina, A. Zapf, A. Cotté, N. Müller and M. Beller, Synthesis, 2008, 3351. For isolated examples of cyanation of alkenyl halides relying on the use of stoichiometric copper(I) cyanide in highly polar solvents at high temperatures (classical Rosenmund-von Braun conditions), see (a) Y. Kitano, T. Matsumoto, T. Wakasa, S. Okamoto, T. Shimazaki, Y. Kobayashi, F. Sato, K. Miyaji and K. Arai, Tetrahedron Lett., 1987, 28, 1565. (b) J. Fitzgerald, W. Taylor and H. Owen, Synthesis, 1991, 686. (c) R. Ostwald, P.-Y. Chavant, H. Stadtmüller and P. Knochel, J. Org. Chem., 1994, 59, 4143. (d) T. Tojo,; Q. Wang,; T. Okuno,; T. Yokomizo and Y. Kobayashi, Synlett, 2013, 24, 1545. (e) S. Eddarir, M. Kajjout and C. Rolando, Tetrahedron Lett., 2012, 68, 603. For the copper(I)-mediated cyanation of styrenyl bromides with potassium hexacyanoferrate(II), see: (f) D. Saha, L. Adak, M. Mukherjee and B. C. Ranu, Org. Biomol. Chem., 2012, 10, 952. For an isolated example of a copper(II)-mediated cyanation of styryl bromide with acetonitrile, see: (g) R.-J. Song, J.-C. Wu, Y. Liu, G.-B. Deng, C.-Y. Wu, W.-T. Wie and J.-H. Li, Synlett, 2012, 23, 2491. For general reviews and monographs on copper catalysis, see: (a) G. Evano, N. Blanchard and M. Toumi, Chem. Rev., 2008, 108, 3054. (b) F. Monnier and M. Taillefer, Angew. Chem., Int. Ed., 2009, 48, 6954. (c) G. Evano, C. Theunissen and A. Pradal, Nat. Prod. Rep., 2013, 30, 1467. (d) Copper-Mediated Cross-Coupling Reactions, G. Evano and N.Blanchard, Eds.; Wiley: Hoboken, 2013. Selected contributions from our research group employing copper catalysis: (a) M. Toumi,; F. Couty,; G. Evano, Angew. Chem., Int. Ed., 2007, 46, 572. (b) M. Toumi, F. Couty, J. Marrot and G. Evano, Org. Lett., 2008, 10, 5027. (c) A. Coste, G. Karthikeyan, F. Couty and G. Evano, Angew. Chem., Int. Ed., 2009, 48, 4381. (d) G. Evano, M. Toumi and A. Coste, Chem. Commun., 2009, 4166. (e) A. Coste, F. Couty and G. Evano, Org. Lett., 2009, 11, 4454. (f) K. Jouvin, F. Couty, G. Evano, Org. Lett., 2010, 12, 3272. (g) G. Evano, K. Tadiparthi and F. Couty, Chem. Comm., 2011, 47, 179. (h) K. Jouvin, A. Bayle, F. Legrand and G. Evano, Org. Lett., 2012, 14, 1652. (i) A. Laouiti, M. M. Rammah, M. B. Rammah, J. Marrot, F. Couty and G. Evano, Org. Lett., 2012, 14, 6. (j) C. Tresse, C. Guissart, S. Schweizer, Y. Bouhoute, A.-C. Chany, M.-L. Goddard, N. Blanchard and G. Evano, Adv. Synth. Catal., 2014, 356, 2051. For the use of acetone cyanohydrin in selected metal-catalyzed cyanations, see: (a) M. Sundermeier, A. Zapf and M. Beller, Angew. Chem., Int. Ed., 2003, 42, 1661. (b) T. Schareina, A. Zapf, A. Cotte, M. Gotta and M. Beller, Adv. Synth. Catal., 2011, 353, 777. Also see refs 21d, 22 and 23b
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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.
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A vinylic Rosenmund-von Braun reaction: practical synthesis of acrylonitriles Alexandre Pradal and Gwilherm Evano*a
ChemComm Accepted Manuscript
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COMMUNICATION
An efficient system based on acetone cyanohydrin and catalytic amounts of copper(I) iodide and 1,10-phenanthroline is reported for the cyanation of alkenyl iodides. A wide range of polysubstituted acrylonitriles could be obtained in fair to good yields and with complete retention of the geometry of the double bond. This extension of the Rosenmund-von Braun reaction also enabled a straightforward formal synthesis of the naturally occurring acrylonitrile alliarinoside. In addition to being versatile intermediates and building blocks for chemical synthesis, conjugated nitriles – frequently named acrylonitriles – are commonly found in natural products including hemi-phorboxazole A 1,1 simmondsin 2,2 calyculin A 23 (an inhibitor of protein phosphatases 1 and 2a), and the whole family of cyanoethylene glucosides natural products such as 4-6 (Figure 1).4 They are also at the core structure of various biologically active molecules, the most representative examples being the well-known tyrphostins family of tyrosine phosphorylation inhibitors 7.5 Selected examples of biologically relevant alkenyl nitriles6 also include trilostane 8,7 commercialized under the brand name Modrenal® and used for the treatment of Cushing’s disease and breast cancer, the nonnucleoside reverse transcriptase inhibitor rilpivirin 9,8 one of the most potent anti-HIV agents, or entacapone 10,9 whose use in combination with levodopa and carbidopa has been shown to improve the treatment of the symptoms of the Parkinson’s disease. Standard methods for the synthesis of alkenyl nitriles, mostly based on classical Wittig,10 Horner-Wadsworth-Emmons,11 and Peterson olefinations,12 suffer from severe limitations such as poor substrate scope, limited efficiency for the synthesis of polysubstituted acrylonitriles and/or poor E/Z selectivity. Although generally quite efficient, similar shortcomings are however found with other routes to conjugated nitriles based on dehydration of acrylamides or conjugated oximes,13 Heck reaction,14 cross-metathesis,15 carbocyanation of alkynes16 or direct allylic cyanation.17,18 An interesting alternative is based on the metal-catalyzed cyanation of alkenyl halides which, provided that the configuration of the double bond is fully retained during the cross-coupling and that no isomerization of the sensitive conjugated nitrile occurs, offers one of the most efficient routes to acrylonitriles. While several catalytic systems based on nickel,19 cobalt20 and palladium21 have been reported for this transformation over the years, most of them still
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Figure 1 Acrylonitrile-containing natural and/or biologically active molecules.
Chem. Commun., 2014, 00, 1-3 | 1
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display poor substrate scope (i.e. limitation to the synthesis of cinnamonitriles, poor yields starting from alkenyl iodides…), require harsh conditions and/or highly toxic reagents or rely on the use of expensive metal complexes and ligands. Based on these limitations, the use of a copper-based catalytic system that would enable expanding the Rosenmund-von Braun cyanation of aryl halides22,23 to the use of alkenyl halides seems an attractive option that has been for some reason rather underestimated.24 Motivated by the potential of such a reaction and based on our experience in copper catalysis,25,26 we decided to study the feasibility of a vinylic Rosenmund-von Braun reaction. We report in this manuscript an efficient system enabling the copper-catalyzed cyanation of a wide range of alkenyl halides with good efficiency and with complete retention of the double bond geometry. To evaluate the feasibility of this vinylic Rosenmund-von Braun reaction, the cyanation of (E)-p-methoxy--iodostyrene 11a was chosen as a test transformation. Different standard sources of cyanide were briefly evaluated for this reaction using a catalytic system inspired from the one reported by Taillefer in the aromatic series.23b As shown in Scheme 1, potassium hexacyanoferrate(II), K4[Fe(CN)6], an attractive non-toxic cyanation reagent, and sodium cyanide did not allow for a full conversion of 11a and only gave the cyanation product 12a in poor yields. Switching to potassium cyanide was found to be a lot more efficient since full conversion could be obtained with this reagent as well as a reasonable yield (80%) of the desired acrylonitrile 12a. A combination of acetone cyanohydrin 27 and tributylamine was found to be equally efficient and, due to its lower toxicity compared to potassium cyanide, was therefore selected as the cyanation reagent.
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ChemComm further derivatization. Moreover, a complete retention of the double bond geometry was observed in all cases since both E and Z starting iodoalkenes 11a-f and 11g-j could be transformed to the corresponding conjugated nitriles without isomerization, and even the corresponding Z-cinnamonitriles 12g-j could be obtained in good yields and high diastereoisomeric ratio. As a note, reacting the brominated analogue of 11a under the exact same reaction conditions failed to provide the corresponding conjugated nitrile 12a and attempts at using additional potassium iodide to perform an in situ vinylic Finkelstein reaction prior to the cyanation failed.
Scheme 1 Selection of the cyanation reagent (Yields and conversions determined by 1H NMR using diphenylmethane as internal standard)
Having demonstrated the possibility of expanding the Rosenmund-von Braun reaction in the vinylic series based on the use of a simple and readily available catalytic system, we moved to the assessment of the substrate scope of this transformation. As shown in Figure 2, this copper-catalyzed cyanation enabled the synthesis of a collection of diversely substituted alkenyl nitriles 12 from the corresponding readily available iodoalkenes 11. As evidenced by these results, a wide range of -iodo-styrene derivatives 11a-j could be readily transformed to the corresponding cinnamonitriles 12a-j that could be isolated in fair to good yields, regardless their steric and electronic properties. Electron-withdrawing and -donating groups were indeed shown to have little influence on the outcome of the reaction and, interestingly, a total chemoselectivity was observed starting from (E)-p-bromo--iodostyrene 11d which gave the corresponding acrylonitrile 12d without competitive cyanation of the aromatic bromide, therefore providing an excellent starting point for
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Figure 2 Copper-catalyzed cyanation of alkenyl iodides: scope and limitations (* reaction performed on a 5 mmol scale).
Importantly, the reaction is not limited to the small scale used for the scope and limitation studies and could be easily performed on a 5 mmol scale with similar efficiency, the low price of both the copper catalyst and the ligand being in addition an important beneficial point for the scale up of this reaction. Furthermore, the reaction could be efficiently extended to the synthesis of -alkyl-substituted acrylonitriles as shown with the preparation of 12k-p. To our delight, both E and Z -substituted iodoalkenes 11k,l and 11m,n were readily transformed to the corresponding cyanated products 12k,l and 12m,n in good yields and with complete retention of the geometry of the double bond. Even more interestingly, ,-disubstituted acylonitriles could also be easily
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ChemComm obtained, as demonstrated with the synthesis of 12o and 12p that could be obtained in 79 and 74% yield, respectively. We finally found that substitution close to the reacting center was equally well tolerated, as shown with the copper-catalyzed cyanation of 11r under standard conditions giving -substituted acrylonitrile 12r in 66% yield. The reaction was however shown to proceed less efficiently in the absence of a substituent in the -position, the corresponding acrylonitriles such as 12q being much less stable and more susceptible to undergo various side-reactions such as conjugated addition, which probably accounts for the lower efficiency of the copper-catalyzed cyanation involving such substrates. Finally, it ought to be mentioned that a number of substituents are well tolerated in the reaction, such as silyl ethers, ethers, acetals or benzylic positions. The possibility of performing a double cyanation was then briefly evaluated starting from substrate 13 possessing two vinyl iodides (Scheme 2). Under the standard conditions, the two vinyl iodides in 13 could be readily cyanated, providing bis-acrylonitrile 14, which could be isolated in reasonable yield (50%) provided that the reaction was run for 42 hours.
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COMMUNICATION combination of copper(I) iodide and 1,10-phenanthroline as the ligand, was shown to be rather general, totally stereospecific and its synthetic utility was exemplified in a three-step formal synthesis of alliarinoside, a naturally occurring acrylonitrile. Besides its broad scope, the main advantage of this procedure lies in the availability and low cost of both the copper source and ligand required for this transformation that provides a direct and selective access to a collection of conjugated nitriles from readily available iodoalkenes.
Scheme 2 Copper-catalyzed double cyanation of a bis-vinyl iodide
We finally wanted to further test our procedure and evaluate its efficiency for the synthesis of more complex and sensitive acrylonitriles. With this goal in mind, we chose alliarinoside 4, a naturally occurring acrylonitrile,4d as a target and decided to check whether the copper-catalyzed cyanation of the corresponding iodoalkene could provide a valuable and synthetically useful route to this natural product. Z-Vinyl iodide 17 was therefore prepared by a Königs-Knorr glucosylation of readily available (Z)-3-iodoprop-2-en1-ol 16 with commercially available peracetyl -D-glucopyranosyl bromide 15 as shown in Scheme 3. Upon reaction with acetone cyanohydrin and tributylamine in the presence of 10 mol% copper(I) iodide and 20 mol% of 1,10-phenanthroline in DMF for 16h, we were pleased to isolate peracetyl-alliarinoside 18, a precursor of alliarinoside 4,4d in 59% yield on a 0.8 g scale and as a single Zisomer, therefore demonstrating the efficiency of the copper-catalyzed vinylic Rosenmund-von Braun reaction. Indeed, compared to the previously reported route to alliarinoside 4 in which the conjugated nitrile was installed from the corresponding aldehyde – itself obtained by ozonolysis of peracetyl-O-allyl--D-glucose – by the means of a Horner-Wadsworth-Emmons olefination yielding the desired Zacrylonitrile and its E-isomer in a 65:35 ratio,4d the use of a coppercatalyzed cyanation allows for a selective synthesis of alliarinoside 4 in addition to reducing the number of steps required for its preparation.
Scheme 3 Application of the copper-catalyzed cyanation to the formal synthesis of alliarinoside
Notes and references a
Laboratoire de Chimie Organique, Service de Chimie et PhysicoChimie Organiques, Université Libre de Bruxelles, Avenue F. D. Roosevelt 50, CP160/06, 1050 Brussels, Belgium. Fax: +32 2 650 27 98; Tel: +32 2 650 30 57; E-mail: [email protected]. † The authors thank the Université Libre de Bruxelles and the FNRS (Incentive Grant for Scientific Research n° F.4530.13) for support. Electronic Supplementary Information (ESI) available: Experimental procedures, characterization, copies of 1H and 13C NMR spectra for all new compounds. See DOI: 10.1039/c000000x/ 1 2 3 4
Conclusions In conclusion, we have developed an efficient copper-catalyzed cyanation of alkenyl iodides which provides a straightforward, practical and robust entry to conjugated nitriles. This extension of the Rosenmund-von Braun reaction in the vinylic series, which relies on the use of acetone cyanohydrin as the cyanation reagent and on a
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