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 C₂[dbnd]C₃ 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.