Carbohydrate-derived propargylic esters react with Et2Zn and catalytic Pd(0), in the presence of a Lewis acid, to generate nucleophilic allenyl metal species capable of intramolecular addition to a tethered carbonyl group. This results in the formation of enantiomerically pure functionalized cyclopentanes with high stereoselectivity and in preparatively useful yields. A high preference is observed for a trans relationship between the alkynyl and OH groups in the cyclopentane products, implying that the cyclization proceeds through open transition states.
在
路易斯酸存在的情况下,
碳水化合物衍生的
丙炔酯与 Et2Zn 和催化
钯(0)发生反应,生成亲核的烯基
金属物种,能够与系留的羰基发生分子内加成反应。这就形成了对映体纯度很高的官能化
环戊烷,具有很高的立体选择性和制备有用的产率。
环戊烷产物中的炔基和羟基之间的反式关系具有很高的偏好性,这意味着环化是通过开放的过渡态进行的。