通过将不对称的双格氏试剂和单格氏试剂添加到苯并噻二磷(1)中,非对映选择性地合成了非对称烷基膦酸酯,并以硫化物的形式分离出来。产物的相对顺/反比取决于所用单格氏试剂的空间位阻。NMR和立体选择性数据的准确分析显示,六配位磷中间体在驱动反应的立体化学结果中起着基本作用。试剂1的特定双环和折叠结构强烈稳定了反应中涉及的超配位磷物质,并有利于它们的形成。已检测到五配位和亚稳定的六配位磷物种,并通过以下方法研究了它们的演变31 P NMR光谱。试剂1和偶合双格氏试剂5 /单格氏试剂之间反应的非对映选择性结果已通过涉及磷六配位的关键步骤进行了解释。
Diastereoselective reactions of 1 4-bis(bromomagnesio)pentane with lactones and cyclic anhydrides
作者:P. Canonne、R. Boulanger、M. Bernatchez
DOI:10.1016/s0040-4020(01)80084-3
日期:1989.1
the stereochemical control of the intramolecular Grignard reaction can be attributed to the chelation between the groups in ortho position of the intermediate oxoalkyl magnesium compound. The alkoxy and the carboxylate seem to have an opposite effect. Furthermore, reactions of 1, 4-bis(bromomagnesio)pentane with non-aromatic cyclicanhydrides yield preferentially the trans diastereoisomer.