Structural and solvent effects on the mechanism of base-induced rearrangement of epoxides to allylic alcohols
Structural and solvent effects on the mechanism of base-induced rearrangement of epoxides to allylic alcohols
复制标题
结构和溶剂对碱诱导环氧化物重排为烯丙醇机制的影响
作者：
Morgan;Gronert
结合实验和计算研究，探讨了结构和溶剂对环戊烯和环己烯氧化物碱催化异构化反应的影响。已知环氧环己烷在非极性溶剂中通过顺式β-消除重排。环戊烯氧化物在非极性溶剂中由于α-质子的不寻常酸性而不是由于不利的构象而经历α-消除为类卡宾中间体。在HMPA中，环戊烯氧化物经历β-消除。为了探索这种机制变化的起源，氘标记的顺式-4-叔丁基环氧环己烷在HMPA中重排，并发现通过反β-消除反应，推测环戊烯氧化物和其他环氧化物也是如此。
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.