Abstract Replacement of C-4 with a hetero substituent (NR, O, S) in the 1-vinyl-3, 4- dihydronaphthalene system has provided a new type of diene for participation in the McCormack cycloaddition reaction with P (III) halides. The tricyclic phospholene oxides so obtained are the first to bear an additional heteroatom in the ring system. 1, 2-Dihydro-7- methoxy-1-(p-toluenesulfonyl)-4-vinylquinoline is a stable solid that reacts with ...