Comparative Reactivity of Different Types of Stable Cyclic and Acyclic Mono- and Diamino Carbenes with Simple Organic Substrates

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• 作者：David Martin ; Yves Canac ; Vincent Lavallo ; Guy Bertrand
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：April 2, 2014
• 年：2014
• 卷：136
• 期：13
• 页码：5023-5030
• 全文大小：437K
• 年卷期：v.136,no.13(April 2, 2014)
• ISSN：1520-5126

文摘

A series of stable carbenes, featuring a broad range of electronic properties, were reacted with simple organic substrates. The N,N-dimesityl imidazolylidene (NHC) does not react with isocyanides, whereas anti-Bredt di(amino)carbene (pyr-NHC), cyclic (alkyl)(amino)carbene (CAAC), acyclic di(amino)carbene (ADAC), and acyclic (alkyl)(amino)carbene (AAAC) give rise to the corresponding ketenimines. NHCs are known to promote the benzoin condensation, and we found that the CAAC, pyr-NHC, and ADAC react with benzaldehyde to give the ketone tautomer of the Breslow intermediate, whereas the AAAC first gives the corresponding epoxide and ultimately the Breslow intermediate, which can be isolated. Addition of excess benzaldehyde to the latter does not lead to benzoin but to a stable 1,3-dioxolane. Depending on the electronic properties of carbenes, different products are also obtained with methyl acrylate as a substrate. The critical role of the carbene electrophilicity on the outcome of reactions is discussed.