Transition-Metal Catalyzed Oxidative Spirolcyclization of N-Aryl Alkynamides with Methylarenes under Microwave Irradiation

A practical synthetic route to construct a variety of 3-benzyl spiro[4,5]trienones was developed via transition-metal Cu/Ag-catalyzed oxidative ipso-annulation of activated alkynes with unactivated toluenes using TBPB as an oxidant under microwave irradiation. This method allows the formation of two carbon-carbon bonds and one carbon-oxygen bond in a single reaction through a sequence of C-H oxidative coupling, ispo-carbocyclization and dearomatization. The advantage of this protocol is operational simplicity, broad substrate scope, and moderate to good yields.