UNSYMMETRICAL DIENOPHILES AND THEIR REACTIONS WITH ORTHO-QUINODIMETHANES

Three unsymmetrical chiral dienophiles have been synthesized and their reactivities with alpha-hydroxy-ortho-quinodimethanes have been asses sed. Thus, the methyl (S)-lactyl esters of trans-4-bromocrotonate and trans-4-acetoxycrotonate (1 and 2) and mono (methyl (S)-lactyl) fumara te 3 were synthesized. Each was reacted with alpha-hydroxy-o-quinodime thane and alpha-hydroxy-alpha-phenyl-o-quinodimethane. While reaction with alpha-hydroxy-o-quinodimethane gave synthetically useful yields o f cycloadducts with high regioselectivity and diastereoselectivity, th e corresponding reactions with alpha-hydroxy-alpha-phenyl-o-quinodimet hane were less successful. The reaction of 3 with alpha-hydroxy-alpha- phenyl-o-quinodimethane also gave a mixture of cycloadducts.