α- vs Ortho-Lithiation of N-Alkylarylaziridines: Probing the Role of the Nitrogen Inversion Process

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• 作者：Francesco Affortunato ; Saverio Florio ; Renzo Luisi ; Biagia Musio
• 刊名：Journal of Organic Chemistry
• 出版年：2008
• 出版时间：December 5, 2008
• 年：2008
• 卷：73
• 期：23
• 页码：9214-9220
• 全文大小：310K
• 年卷期：v.73,no.23(December 5, 2008)
• ISSN：1520-6904

文摘

The lithiation reaction of monophenyl- and diphenylaziridines has been investigated in detail in an effort to understand why the former undergo exclusively or mainly ortho-lithiation while the latter are lithiated exclusively at the α-position. Evidence is reported that ruled out the possibility that the α-lithiation, observed for the diphenylaziridines, is the result of an ortho- to α-translocation phenomenon, thus substantiating a direct α-deprotonation process. The role of the aziridine nitrogen lone-pair has been considered: dynamics at the aziridine nitrogen as well as complex-induced proximity effects seem to be responsible for the observed regioselectivity in both monophenyl and diphenylaziridines. It turns out that, by tuning the reaction conditions for the lithiation of trans-1-alkyl-2-methyl-3-phenylaziridines, it is possible to generate with high regioselectivity α- and/or ortho-lithiated aziridines, which can be stereoselectively functionalized by electrophilic trapping. A regioselective ortho-functionalization of diphenylaziridines is made possible by halogen− or tin−lithium exchange and by deprotonation of bis-deuterated aziridines.