SYNTHESIS AND DIENOPHILIC REACTIVITY OF 1,2-DIFLUOROVINYLPHENYLSULFONE

1,2-Difluorovinylphenylsulfone 5 was conveniently prepared in three st eps from chlorotrifluoroethylene. Both E and Z isomers of 5 gave excel lent yields of [4+2] cycloadducts with cyclopentadiene. The E isomer r eacted with high kinetic exo selectivity. 1,2-Difluorovinylphenylsulfo ne 5 did not give cycloadducts with highly polar and reactive dienes. Only complex mixtures were obtained. This was assigned to competitive pathways resulting from addition-elimination sequences. Products resul ting from such an addition-elimination sequence were obtained from rep resentative nucleophilic reagents. (C) 1997 Elsevier Science Ltd.