Divergent synthesis of chromones and chromanones from diketones using an AgOTf/[Si]H system by switching hydrosilanes

A method of using AgOTf/[Si]H for the efficient and divergent synthesis of chromones and chromanones from a common substrate via reductive coupling cyclization by switching hydrosilanes has been developed. Results of mechanistic studies revealed that under Ph2MeSiH conditions, the reaction initially undergone cyclization to form chromones 2a, which can subsequently be reduced to yield chromanones 3a. When the hydrosilane was switched to Et3SiH, the reaction route stopped at chromone 2a and C2C3 could not be further reduced. This novel, mild protocol features broad functional group compatibility, high product diversity, and utility in constructing biorelevant chromone or chromanone derivatives.