The formation of alkylidenezinc carbenoids by 1,4-addition/carbozincation of dialkylzincs or alkyl iodides based on zinc atom radical transfer, in the presence of dimethylzinc with β-(propargyloxy)enoates having pendant iodo- and bromoalkynes, is disclosed. Formation of the carbenoid intermediate is fully stereoselective at −30 °C and arises from a formal anti-selective carbozincation reaction. Upon warming, the zinc carbenoid is stereochemically labile and isomerizes to its more stable form.
1,4-加成/碳锌化反应在二烷基锌或烷基碘化物基础上形成烷基亚锌卡宾,存在二甲基锌和具有挂链碘代和溴代炔基的β-(丙炔氧基)烯酸酯。卡宾中间体的形成在-30°C时完全立体选择性,并源自一个形式上的反式选择性碳锌化反应。随着升温,锌卡宾在立体化学上是不稳定的,并异构为更稳定的形式。