Facile Benzylic Alkylation of Arenes with Alcohols by Catalysis with Spirocyclic NHC Ir^III Pincer Complex

Abstract

A facile benzylic alkylation of indenes and other arenes was developed from readily available primary and secondary alcohols using our newly investigated CCC pincer Ir^III catalyst (SNIr-H). Excellent regioselectivity and yield (89 %) of the C3-alkylated indenes were obtained. Additionally, the challenging sp² C-alkylation was readily accomplished. This method could be utilized for the synthesis of the analogs of a histamine H1 receptor antagonist and the functional material template molecule, indeno[2,1-a]indene. A hemilabile Ir^III -dihydride intermediate was proposed based on control experiments and previous density functional theory (DFT) calculations for the borrowing hydrogen mechanism and is key to the success of this Ir^III catalyst in the reduction of unactivated multi-substituted olefin intermediates.