Highly stereoselective formal [3+3] cycloaddition of enals and azomethine imines catalyzed by N-heterocyclic carbenes
Highly stereoselective formal [3+3] cycloaddition of enals and azomethine imines catalyzed by N-heterocyclic carbenes
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DOI：
10.1021/ja0709167
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发表时间：
2007-05-02
影响因子：
15
通讯作者：
Scheidt, Karl A.
中科院分区：
文献类型：
--
作者：
Chan, Audrey;Scheidt, Karl A.
衍生自N-均三甲苯基苯并咪唑鎓盐的N-杂环卡宾是用于由α，β-不饱和醛生成高烯醇化物物质的有效催化剂。亲核中间体添加到偶氮甲亚胺亚胺，并且所得的活化羰基单元经历分子内酰化事件。α，β-不饱和醛与甲亚胺在NHC催化下的[3 + 3]环加成反应，以良好的产率和高的非对映选择性（> 20：1）得到取代的哒嗪酮。NHC催化的反应包括芳族和烷基α，β-不饱和醛和各种芳族偶氮甲亚胺亚胺。在加入醇或胺时，哒嗪酮可以进行选择性六元开环，得到酯和酰胺。
N-Heterocyclic carbenes derived from N-mesityl benzimidazolium salts are effective catalysts for generating homoenolate species from alpha,beta-unsaturated aldehydes. The nucleophilic intermediate adds to azomethine imines, and the resulting activated carbonyl unit undergoes an intramolecular acylation event. This formal [3 + 3] cycloaddition between alpha,beta-unsaturated aldehydes and azomethine imines catalyzed by NHC has been developed to give substituted pyridazinones in good to excellent yields with high diastereoselectivity (> 20:1). The NHC-catalyzed reaction accommodates aromatic and alkyl alpha,beta-unsaturated aldehydes and various aromatic azomethine imines. The pyridazinones can undergo selective six-membered ring opening upon addition of alcohols or amines to give esters and amides.