Synthesis of pyrrolizin-3-ones by flash vacuum pyrolysis of pyrrol-2-ylmethylidene Meldrum’s acid derivatives and 3-(pyrrol-2-yl)propenoic esters
作者:Shirley E. Campbell、Murray C. Comer、Paul A. Derbyshire、Xavier L. M. Despinoy、Hamish McNab、Roderick Morrison、Craig C. Sommerville、Craig Thornley
DOI:10.1039/a701749i
日期:——
Monosubstituted pyrrolizin-3-ones 1 with substituents at the 1-, 5-,
6- or 7-positions are prepared in excellent yield by flash vacuum
pyrolysis (FVP) of appropriate Meldrumâs acid derivatives 2. The
mechanism involves formation of the pyrrol-2-ylmethylideneketene 29,
which can also be generated thermally from 3-(pyrrol-2-yl)propenoate
esters (e.g. 30). This alternative route has been used to make
a range of 2-substituted pyrrolizin-3-ones, again in excellent yield.
The 3-oxo-3H-pyrrolizine-2-carboxylic acid 42 could not be made
in this way owing to facile decarboxylation to pyrrolizinone 1, and
extension to the formation of the azaazulenone 48 was again
unsuccessful.
具有1-、5-、6-或7-位取代基的单取代吡咯并吡嗪-3-酮1通过适当的美尔格酸衍生物2的闪蒸真空热解(FVP)以极佳产率制备。其机理涉及吡咯-2-亚甲基烯酮29的形成,该物质也可通过3-(吡咯-2-基)丙烯酸酯(例如30)的热解生成。这条替代路线已被用于以极佳产率制备一系列2-取代吡咯并吡嗪-3-酮。由于易于脱羧转化为吡咯并吡嗪酮1,3-氧代-3H-吡咯并吡嗪-2-羧酸42无法通过此方法制备,而扩展到制备氮杂蒽酮48的尝试再次失败。