A short and efficient route to peri-fused heterocycles has been developed. The transition metal in cooperation with the imino directing group cleaves the C-P bond of the phosphirane, followed by 1,1-insertion of CO and reductive elimination to give a reactive azaphosphacyclohexone derivative. The further dearomatic Diels-Alder reaction of the in situ-generated azaphosphacyclohexone with alkenes provides an array of annulated heterodecalins with high molecular complexity and atomic utilization.