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.
(<i>Z</i>)-3-<i>p</i>-Tolylsulfinylacrylonitriles as Chiral Dipolarophiles: Reactions with Diazoalkanes
作者:José L. García Ruano、Sergio A. Alonso de Diego、Daniel Blanco、Ana M. Martín Castro、M. Rosario Martín、Jesús H. Rodríguez Ramos
DOI:10.1021/ol016481o
日期:2001.10.1
[reaction: see text] The dipolarophilic reactivity of enantiopure (Z)-3-p-tolylsulfinylacrylonitriles (1) has been evaluated with diazoalkanes. 3-Cyanopyrazoles are obtained when R = H, but with R = alkyl (Bn, n-Bu, and t-Bu) only one cycloadduct (4 or 5) is formed in high yield under mild conditions, therefore evidencing a complete control of the regioselectivity and the endo/exo and pi-facial selectivities