Polycyclic phosphonic acid derivatives obtained by a [4+2] cycloaddition strategy using phosphonodienes

A practical route is described for the preparation of 1-phosphono-3(4-di)-substituted-1,3-butadienes based on the Horner–Wadsworth–Emmons (HWE) reaction. Their reactivity in the Diels–Alder (DA) reaction with three selected dienophiles is studied and compared to diethyl 1-phosphono-1,3-butadiene. A particular attention is given to the P-deprotection of cycloadducts from dibenzyl phosphonodienes. New phosphonated bicycles and tricycles have been obtained using this HWE/DA reaction sequence.