Phosphonodithioformates as heterodienophiles: synthesis of (3,6-dihydro-2H-thiopyran-2-yl)phosphonates

Phosphonodithioformates are shown to be good heterodienophiles in [4+2] cycloadditions with open chain and cyclic dienes. Lewis acids efficiently catalyze this hetero Diels–Alder reaction and a selective radical desulfanylation of the cycloadducts using Bu3SnH leads to new (3,6-dihydro-2H-thiopyran-2-yl) phosphonates.