Distinct reactivities of ortho-chalcone-substituted organophosphines with activated alkynes: skeletal editing or periphery modification

Abstract

Skeletal editing of organophosphines with cleavage of the P–C bond as the key step represents a daunting challenge due to its high dissociation energy. Herein, we report an efficient catalyst-free strategy to cleave P–Ar bonds and insert transformable propionates therein, thus achieving skeletal editing of ortho-chalcone-substituted organophosphines and the ability to generate a range of novel diphenylphosphine-oxide-substituted 2,3-dihydro-1H-indenes with three contiguous stereocenters in a highly diastereoselective fashion. Surprisingly, replacing the propionate with an acetylenedicarboxylate or propiolamide resulted in two further distinct reaction outcomes: Acetylenedicarboxylates served as efficient dienophiles that undergo formal [4 + 2] cycloaddition with ortho-chalcone-substituted organophosphines to afford λ⁵-phosphinines, while propiolamide affords an uncommon P/N-heterocycle, benzo[c][1,2]azaphosphol-3-one.