Stereospecificity and Stereoselectivity in Electrophilic Substitution Reactions of Non-α-Heterosubstituted Organolithiums and Stannanes: A Rotationally Restricted Amide as an Internal Stereochemical Marker
作者:Jonathan Clayden、Madeleine Helliwell、Jennifer H. Pink、Neil Westlund
DOI:10.1021/ja0112590
日期:2001.12.19
complete stereochemical course of a tin-lithium exchange/electrophilic quench sequence has been unambiguously determined by stereochemical characterization (using X-ray crystallography or NOE studies) at every step. Pairs of diastereoisomeric stannanes of known stereochemistry bearing atropisomeric amide substituents undergo tin-lithium exchange with alkyllithiums to give diastereoisomeric benzylic organolithiums
锡-锂交换/亲电猝灭序列的完整立体化学过程已通过每一步的立体化学表征(使用 X 射线晶体学或 NOE 研究)明确确定。具有阻转异构酰胺取代基的已知立体化学的非对映异构锡烷对与烷基锂进行锡-锂交换,得到非对映异构的苄基有机锂,其立体化学可以通过 NMR 确定。对于锡烷的一种阻转异构体,锡-锂交换是完全立体定向的,并保留立体化学。另一种阻转异构体进行非立体有择的锡-锂交换:这是第一个报道的锡对锂的亲电取代缺乏立体有择性的例子。通过锡-锂交换产生的一种非对映异构阻转异构有机锂被氘化和烷基化并保留,但通过立体化学反转而甲锡烷基化。另一个是非立体特异性地烷基化,但保留下来。