SYNTHESIS AND DIENOPHILIC BEHAVIOR OF ENANTIOMERICALLY PURE (Z)-3-P-TOLYLSULFINYLACRYLONITRILES

The syntheses of enantiomerically pure (Z)-3-p-tolylsulfinylacrylonitr ile (1b) and its 2-n-butyl (1a), 2-tert-butyl (1c), and 2-benzyl(ld) d erivatives, by stereoselective hydrocyanation with Et2AlCN of their co rresponding alkynylsulfoxides, are described. Asymmetric Diels-Alder r eactions of these dienophiles with cyclopentadiene are also reported, the most significant finding being their total pi-facial diastereosele ctivity, controlled by the sulfur configuration, which can be readily invented by using BF3 as a catalyst. The endo selectivity is very high for Ib under thermal and catalytic (ZnBr2) conditions and complete in the presence of BE3 whereas la and Id only exhibit a complete endo se lectivity in the presence of BF3.