Synthesis of C2-Alkyl Quinazolinones through Bis(pinacolato)diborane Mediated Transfer Hydrogenation Reaction of Alkynes to Alkanes

Herein, we report a facile approach to prepare a variety of C2-alkyl-substituted quinazolinones in good to excellent yields and high reduction selectivity through bis(pinacolato)diborane (B₂Pin₂)-mediated transfer hydrogenation of an alkyne to an alkane under mild reaction conditions. Control experiments revealed that MeOH as the green hydrogen source and B₂Pin₂ was converted to nucleophilic species in the presence of MeOH and base. More importantly, the reaction was easily performed in gram scales and quinazolinone-derived estrone could be obtained in good yield over three steps. The present method features broad substrate scope, good functional group tolerance, green hydrogen source, and borate-mediated transfer hydrogenation.