结构和溶剂对碱诱导环氧化物重排为烯丙醇机理的影响。

Structural and solvent effects on the mechanism of base-induced rearrangement of epoxides to allylic alcohols.

作者信息

Morgan KM, Gronert S

机构信息

Department of Chemistry, College of William & Mary, P.O. Box 8795, Williamsburg, Virginia 23187, and Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, USA.

出版信息

J Org Chem. 2000 Mar 10;65(5):1461-6. doi: 10.1021/jo991619q.

DOI:10.1021/jo991619q

PMID:10814110

Abstract

A combined experimental and computational study is presented which explores the influence of structure and solvent on the base-catalyzed isomerization of cyclopentene- and cyclohexene oxides. Cyclohexene oxide is known to rearrange via a syn beta-elimination in nonpolar solvents. Cyclopentene oxide instead undergoes alpha-elimination to a carbenoid intermediate in nonpolar solvents due to the unusual acidity of the alpha-proton, not because of an unfavorable conformation. In HMPA, cyclopentene oxide undergoes beta-elimination. To explore the origins of this mechanistic change, deuterium-labeled cis-4-tert-butylcyclohexene oxide was rearranged in HMPA and was found to react via anti beta-elimination, as presumably do cyclopentene oxide and other epoxides.

摘要

本文介绍了一项结合实验与计算的研究，该研究探讨了结构和溶剂对环戊烯氧化物和环己烯氧化物碱催化异构化的影响。已知环己烯氧化物在非极性溶剂中通过顺式β-消除进行重排。相反，环戊烯氧化物由于α-质子的异常酸性，在非极性溶剂中会发生α-消除生成类卡宾中间体，而不是因为构象不利。在六甲基磷酰胺（HMPA）中，环戊烯氧化物会发生β-消除。为了探究这种机理变化的根源，对氘标记的顺式-4-叔丁基环己烯氧化物在HMPA中进行重排，发现其通过反式β-消除反应，环戊烯氧化物和其他环氧化物可能也是如此。