the latter to 3-oxidopyrylium ylide precursors. The cycloadducts can be readily desulfinylated to afford enantiomerically pure oxa-bridged bicyclo[5.3.0]decane ring systems. Theoretical calculations confirm that diastereoselectivity stems from the conformational preferences of the alkenylsulfoxide unit in the transition state of the reaction.
[反应:见正文]在烯烃的反式末端位置引入同手性对
甲苯磺酰基会在后者的分子内环加成反应中向3氧化
吡啶鎓叶立德前体产生总的非对映异构分化作用。环加合物可以容易地脱
硫,以提供对映体纯的氧杂桥联
双环[5.3.0]癸烷环系统。理论计算证实非对映选择性源于反应过渡态链烯基亚砜单元的构象偏好。