Catalyst and pressure dependent reductive cyclizations for the diastereo-selective synthesis of hexahydropyrrolo[1,2-<i>a</i>]quinoline-5-carboxylic esters
作者:Richard A. Bunce、James E. Schammerhorn、Legrande M. Slaughter
DOI:10.1002/jhet.5570430613
日期:2006.11
A diastereoselective synthesis of 1,2,3,3a,4,5-hexahydropyrrolo[1,2-a]quinoline-5-carboxylic esters has been developed using a tandem reduction-double reductive amination reaction. The nitro dicarbonyl cyclization substrates were synthesized by alkylation of methyl (2-nitrophenyl)acetate with 2-bromomethyl-1,5-hexadiene derivatives, followed by ozonolysis. Catalytic hydrogenation of each substrate
利用串联还原-双还原胺化反应,开发了一种非对映选择性的1,2,3,3a,4,5-六氢吡咯并[1,2- a ]喹啉-5-羧酸酯。硝基二羰基环化底物的合成方法是,将(2-硝基苯基)乙酸甲酯与2-溴甲基-1,5-己二烯衍生物进行烷基化,然后进行臭氧分解。每种底物的催化加氢给出了目标杂环,以及脱酰基产物和由侧链羰基捕获中间羟胺所产生的加合物。产物比率随催化剂和氢气压力而显着变化。标题化合物的环化反应具有很高的非对映选择性,产生每种六氢吡咯并[1,2- a] -喹啉如与清一色单一立体异构体顺式几何形状。在先前的杂环研究中未观察到竞争过程,但可归因于系统中更大的应变,这减慢了最终的环闭合。