硫叶立德途径立体控制合成乙烯基型环氧化合物

Stereoselective Synthesis of Vinyloxirane via Sulfonium Ylides

在相转移条件下(CH_3CN/KOH/RT)乙烯基型硫叶立德和醛反应高产率地得到以反式为主的产物,而在低温溴化锂存在下(LiBr/KHMDS/THF/-90℃)得到以顺式为主的产物.对于通过反应条件的变化而改变反应产物立体化学的机理,给出了一个初步的解释.

Under the phase - transfer condition (CH3CN/KOH/RT), the reaction of the vinyl - type sulfonium ylides and aldehydes gives mainly trans - vinyloxirane, while at low temperature in the presence of lithium bromide (LiBr/KHMDS/THF/ - 95 ℃ ) the main product is cis - vinyloxiranes. A possible mechanism for the tuning of the reaction stereochemistry by simply varing the reaction conditions is proposed.