Regio- and Stereoselective 1,3-Oxathiolane Formation in the Reaction of Thiolactones with Optically Active Oxiranes
作者:Changchun Fu、Anthony Linden、Heinz Heimgartner
DOI:10.1002/hlca.200490205
日期:2004.9
either in the presence of SiO2 or under more-drastic conditions with BF3⋅Et2O or SnCl4 (Scheme 8). The results show that spirocyclic 1,3-oxathiolanes can be prepared from thiolactones with oxiranes. The nucleophilic attack of the thiocarbonyl S-atom at the SiO2-activated oxirane ring proceeds with high regio- and stereoselectivity via an SN2-type mechanism.
3 H-异苯并呋喃-1-硫酮(1)与(S)-2-甲基环氧乙烷(2)和(R)-2-苯基环氧乙烷(6)在SiO 2存在下于无水CH 2 Cl 2中反应2双非对映异构螺环-1,3-氧硫杂环戊烷,的即,3和4与Me基团在C(5'),以及7和8与Ph基团在C(4'),分别为(方案2和3)。在这两种情况下,3 H-异苯并呋喃-1-酮(5)形成为主要产品。3,4-二氢-2 H- [1]苯并吡喃-2-硫酮(9)和3,4,5,6-四氢-2 H-吡喃-2-硫酮(14)与2和6的类似反应分别得到四对相应的非对映异构螺环化合物10和11、12和13、15和16以及18和19(方案4-7)。在14与6的反应中,还形成了在C(2)带有Ph基的1,3-氧杂硫杂环戊烷20。的结构3,7,8,10,19,和20是由X射线晶体学(建立图1-4)。与此相反的硫代内酯1,9,和14中,硫酯21A - 21D不与(反应- [R)-