known absolute configuration. The enantiomeric excess of 10 was determined by alkylation with an optically active lithium compound and that of 14 by an optically active NMR.-shift reagent. The SE′ reaction 10 14 was thus shown to proceed with 94% (97% syn/3% anti) stereoselectivity.
使用旋光性二
硅烷基
硫醚9B的乙
硅烷/二甲
硅烷基
甲烷重排制备旋光性二甲
硅烷基烯烃10,其绝对构型是通过对
溴衍
生物13(P 2 1,a = 7.847(3)Å,b = 9.487(3)Å,c = 20.010(8)Å,β= 82.28°(3),Z = 2)。10的酰化作用提供了光学活性的酮14,该酮被降解为16(一种已知的绝对构型的化合物)。对映体过量10通过用旋光性
锂化合物烷基化来确定R 2,通过旋光性NMR位移试剂通过烷基化来确定14。因此显示出S E '反应10 14以94%(97%syn / 3%抗)立体选择性进行。