Chiral N-heterocyclic carbene catalyzed, enantioselective oxodiene Diels-Alder reactions with low catalyst loadings
Chiral N-heterocyclic carbene catalyzed, enantioselective oxodiene Diels-Alder reactions with low catalyst loadings
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DOI：
10.1021/ja066380r
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发表时间：
2006-11-29
影响因子：
15
通讯作者：
Bode, Jeffrey W.
中科院分区：
文献类型：
--
作者：
He, Ming;Uc, Gerson J.;Bode, Jeffrey W.
手性 N-杂环卡宾 (NHC) 催化外消旋 α-氯醛的氧化还原反应，生成适合高对映选择性逆电子需求 1-氧二烯 Diels−Alder 反应的手性烯醇化物。值得注意的是，这些反应在温和、操作友好的反应条件（EtOAc，室温，2−8 h）下进行，使用少于 1 mol% 的手性 N-异丙基三唑鎓盐作为预催化剂。由容易获得的反应物以优异的产率和优异的对映选择性形成了一系列带有脂肪族或芳香族取代基的密集官能化二氢吡喃-2-酮。通过氯醛在反应条件下的快速差向异构化，避免了外消旋起始原料和手性催化剂之间的立体化学错配。
Chiral N-heterocyclic carbene (NHC) catalyzed redox reactions ofracemicα-chloroaldehydes lead to the generation of chiral enolates suitable for highly enantioselective inverse-electron-demand 1-oxodiene Diels−Alder reactions. Significantly, these reactions proceed under mild, operationally friendly reaction conditions (EtOAc, room temperature, 2−8 h) using less than 1 mol % of a chiralN-mesityl triazolium salt as the precatalyst. A broad array of densely functionalized dihydropyran-2-ones bearing either aliphatic or aromatic substiutents are formed in excellent yields and exceptional enantioselectivities from readily available reactants. Stereochemical mismatching between the racemic starting materials and the chiral catalyst is avoided by rapid epimerization of the chloroaldehydes under the reaction conditions.