Iridium-Catalyzed Intramolecular ß-C-H Alkenylation of Ketones with Alkynes via a Hydride-Transfer Approach.

ABSTRACT

Direct functionalization of carbonyl ß C-H bonds without using directing groups has not been a trivial task, and it is even more challenging to realize the corresponding atom-economical transformations with common alkenes or alkynes as the coupling partner. Here, we describe the development of an iridium-catalyzed intramolecular direct ß-alkenylation of ketones with regular alkynes. The reaction is redox neutral, avoids strong acids or bases, and tolerates various functional groups. The combined experimental and computational mechanistic studies reveal a hydride-transfer pathway, involving ketone α,ß-desaturation, iridium-hydride-mediated alkyne insertion, conjugate addition, and α-protonation.