Facile Benzylic Alkylation of Arenes with Alcohols by Catalysis with a 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 (SNIrÀ H). Excellent regioselectivity and yield (89 %) of the C3-alkylated indenes were obtained. Additionally, the challenging sp 2 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 multisubstituted olefin intermediates.