Maki Brooks E, Chan Audrey, Phillips Eric M, Scheidt Karl A
Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois, 60208.
Tetrahedron. 2009 Apr 18;65(16):3102-3109. doi: 10.1016/j.tet.2008.10.033.
N-Heterocyclic carbenes catalyze the oxidation of allylic and benzylic alcohols as well as saturated aldehydes to esters with manganese(IV) oxide in excellent yields. A variety of esters can be synthesized, including protected carboxylates. The oxidation proceeds under mild conditions, with low loadings of a simple triazolium salt pre-catalyst in the presence of base. Substrates containing potentially epimerizable centers are oxidized while preserving stereochemical integrity. The acyl triazolium intermediate generated under catalytic conditions can be employed as a chiral acylating agent in the desymmetrization of meso-diols.
N-杂环卡宾可催化烯丙醇、苄醇以及饱和醛与二氧化锰反应生成酯，产率优异。可合成多种酯，包括受保护的羧酸盐。该氧化反应在温和条件下进行，在碱存在下使用低负载量的简单三唑鎓盐预催化剂。含有潜在可差向异构化中心的底物在氧化过程中可保持立体化学完整性。催化条件下生成的酰基三唑鎓中间体可作为手性酰化剂用于内消旋二醇的去对称化反应。
