康 · 学术研究 | Reaction of the Day No. 953

Substrate Scope

Large-scale Application

Summary and Comments

Prof. Xiao and his co-workers from University of Liverpool reported the synthesis of chiral piperidines by Rh-catalyzed transfer hydrogenation of pyridinium salts. The authors found that under reductive conditions, simple N-ethylpyridinium salts can undergo amine exchange similar to the Zincke reaction, which allows incorporation of enantiopure α-methylbenzylamine followed by a diastereoselective reduction that results in the formation of a single diastereomer of 2-substituted piperidines. A wide variety of 2-aryl and 2-alkyl substituents were tolerated, and single diastereomers of the products were isolated in good to excellent yields. Some exploration of disubstituted pyridinium salts was made, with fluorine substituents at the 3- or 5-positions led to 2,3-and 2,5-disubstituted piperidines with predominantly cis diastereoselectivity in good to excellent yields. The reaction was demonstrated on a multi-hundred gram scale, showing the potential for this chemistry in the large-scale synthesis of chiral piperidines.

黑池大学Jianliang Xiao教授等发展了一种Rh催化转换成转至一氧化氮里面间体，借助了从最简单叔丁醇灶制品驶向，快速大量具备实用性的左手适度叔丁醇、萘叔丁醇醇。该里面间体具备极佳的立体选择适度、对映体选择适度、羟基容忍适度，其顺利的极为重要是在转换成里面间体必须里面替换成左手适度一级咪唑，这种里面间体操作过程在池里面存有时与构件密切关系透过转至一氧化氮基里面间体，同时在环状构件里面导致左手适度。这种里面间体工具借助了不椭圆乙烯里面间体和多解决办法工具的明显优点和关键问题，通过这种转至一氧化氮里面间体并不需要对叔丁醇透过烷基化和15N-标记，也可以借助奥尼尔级的SB。

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