Lewis Acid/Hexafluoroisopropanol: A Promoter System for Selective ortho-C-Alkylation of Anilines with Deactivated Styrene Derivatives and Unactivated Alkenes

摘要

Aniline derivatives are frequently encountered in molecules of industrial relevance such as dyes or antioxidants, which make the development of synthetic methods for the functionalization of these privileged structures highly sought-after. A general protocol for the hydroarylation of electronically diverse alkenes with anilines would be ideal to provide densely functionalized compounds. However, this transformation has been underexplored compared to more traditional hydroarylation of unactivated alkenes because of the significant challenges associated with the control of the selectivity and its substrate tolerance. Herein, we describe a selective, versatile, and user-friendly ortho-C-alkylation of anilines with alkenes that hinges on the beneficial combination of a Lewis acid (Ca(II)) and hexafluoroisopropanol as a solvent. This protocol allows for the extension of this transformation to highly deactivated styrenes and demonstrates a remarkable improved reactivity regarding aliphatic alkenes, styrene derivatives, and dienes. In addition, DFT computations were performed which, combined with experimental observations, suggest a nearly concerted mechanism that impart the ortho-selectivity.