Synthesis and Dienophilic Behavior of Enantiomerically Pure (<i>Z</i>)-3-<i>p</i>-Tolylsulfinylacrylonitriles
作者:Jose L. García Ruano、Antonio Esteban Gamboa、Ana M. Martín Castro、Jesús H. Rodríguez、M. Isabel López-Solera
DOI:10.1021/jo9721002
日期:1998.5.1
The syntheses of enantiomerically pure (Z)-3-p-tolylsulfinylacrylonitrile (1b) and its 2-n-butyl (1a), 2-tert-butyl (1c), and 2-benzyl(ld) derivatives, by stereoselective hydrocyanation with Et2AlCN of their corresponding alkynylsulfoxides, are described. Asymmetric Diels-Alder reactions of these dienophiles with cyclopentadiene are also reported, the most significant finding being their total pi-facial diastereoselectivity, 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 selectivity in the presence of BF3.