Application of the Mitsunobu reaction to ephedrines and some related amino alcohols. Aspects of intramolecular participation of the amino group
作者:Martin A. Poelert、Richard M. Kellogg、L. A. Hulshof
DOI:10.1002/recl.19941130704
日期:——
at the benzylic hydroxyl group of (1S,2S)-pseudoephedrine (2) to afford (1R,2S)-ephedrine is known to be a difficult process. The Mitsunobureactions of 1 and 2 might offer a route to achieve such inversions. In fact Mitsunobureactions on 1 and 2 are known to proceed via aziridines formed on intramolecular SN2 substitution by the amine functionality. The Mitsunobureactions of N-methylated and N-benzylated
已知将(1S,2S)-伪麻黄碱(2)的苄基羟基上的构型反转以得到(1R,2S)-麻黄碱是一个困难的过程。1和2的Mitsunobu反应可能会提供实现此类反演的途径。实际上,已知在1和2上的Mitsunobu反应是通过分子内S N 2被胺官能团取代形成的氮丙啶进行的。已经发现N-甲基化和N-苄基化的麻黄碱的Mitsunobu反应通过相应的叠氮鎓离子进行。这些吖丙啶鎓离子可以被打开(小号N 2取代)被邻苯二甲酰亚胺和硫醇等亲核试剂所取代。通过使用叔丁氧羰基-(BOC)或苄氧羰基-(CBZ)保护的衍生物,可以避免分子内参与2。这些衍生物上的Mitsunobu反应导致苄基羟基中心的构型反转。相反,1的BOC和CBZ衍生物在Mitsunobu条件下脱保护。的光延反应苏式(1小号,2,小号也已经研究了)-2-氨基-1,3-丙二醇。通过与二甲基甲酰胺二甲基乙缩醛反应实现保护的尝试导致了通过X射线晶体学确
Access to Optically Pure Benzosultams by Superelectrophilic Activation
N-(arenesulfonyl)-aminoalcohols derivedfrom readily available ephedrines or amino acids undergo an intramolecular Friedel–Crafts reaction to afford enantiopure benzosultams bearing two adjacent stereocenters in high yields with fully controlled diastereoselectivity. Low-temperature NMR spectroscopy demonstrated the crucial role played by the conformationally restricted chiral dicationic intermediates.
The stereochemistry of the chlorination reactions with SOCl2 of free ephedrine and pseudoephedrine and their hydrochlorides, oxamides and sulfonamides was analyzed. Chlorination of free and hydrochloride erythro isomers occurs with 100% inversion of configuration at C-1 (SN2 mechanism). Chlorination of oxamides and sulfonamides of erythro isomers occurs with retention of the configuration at C-1, (SNi
分析了游离麻黄碱和伪麻黄碱与SOCl 2氯化反应的立体化学及其盐酸盐,草酰胺和磺酰胺。的自由和盐酸赤式异构体的氯化与C-1(S构型的100%反转发生Ñ 2机构)。赤型异构体的草酰胺和磺酰胺发生氯化反应,保留C-1构型(S N i机理)。所有苏式异构体及其衍生物的盐酸盐,草酰胺或磺酰胺中的氯化反应均得到相同比例的赤型(40%)和苏型(60%)(S N1机制)。用HCl处理DMSO中的盐酸氯脱氧麻黄碱和氯脱氧伪麻黄碱的异构体混合物会改变异构体比例,增加赤型异构体含量(65%)。如果该化合物事先被甲苯磺酸化或转化为酰胺,或者如果该化合物直接被SOCl 2氯化,则使用赤型乙醇胺可以有选择地到达赤型氯胺。