Rearrangement of ammonium ylides produced by intramolecular reaction of catalytically generated metal carbenoids. Part 1. Synthesis of cyclic amines
作者:Clark、Hodgson、Goldsmith、Street
DOI:10.1039/b108179a
日期:2001.12.11
Cyclic amines have been prepared in good yield by [2,3]-rearrangement of ammonium ylides produced by intramolecular reaction of copper carbenoids tethered to allylic amines. Copper(II) acetylacetonate is the optimum catalyst for carbenoid/ylide generation from the diazo ketone precursor, and reactions must be performed at elevated temperatures in order to obtain reasonable reaction rates and high yields. The reaction has been used to prepare five- to eight-membered cyclic amines. In cases where the substrate possesses a substituent on the tether connecting the diazo group to the allylic amine, tandem ylide formation and rearrangement delivers a high yield of the expected 2,5-dialkylpyrrolidinone or 2,6-dialkylpiperidinone, but low levels of diastereocontrol are obtained.Two new methods have been developed for the synthesis of diazo ketones containing a nucleophilic allylic amine substituent. The first method involves conjugate addition of allylic amines
to unsaturated diazo ketones and is high yielding but of limited scope. The alternative general sequence involving nitrogen protection, α-diazo ketone formation, deprotection and allylation can be used to prepare the substrates required for intramolecular tandem ylide formation and rearrangement.
循环胺通过铵亚胺的[2,3]-重排反应得到,铵亚胺是通过与烯基胺相连的铜羧肽的分子内反应生成的。铜(II)乙酰乙酮是从二氮酮前体生成羧肽/亚胺的最佳催化剂,反应必须在高温下进行,以获得合理的反应速率和高产率。该反应已用于合成五到八员环的循环胺。在底物具有连接二氮基与烯基胺的桥梁上的取代基的情况下,串联亚胺的形成和重排能高产率地生成预期的2,5-二烷基吡咯烷酮或2,6-二烷基哌啶酮,但获得的二面角控制水平较低。针对含有亲核烯基胺取代基的二氮酮的合成,开发了两种新方法。第一种方法涉及烯基胺对不饱和二氮酮的共轭加成,产率高但适用范围有限。另一种通用序列包括氮的保护、α-二氮酮的形成、去保护和烯基化,可用于合成所需的底物,以促进分子内的串联亚胺形成和重排反应。