Mechanistic Insight into the Staudinger Reaction Catalyzed by N-Heterocyclic Carbenes
作者:Morgan Hans、Johan Wouters、Albert Demonceau、Lionel Delaude
DOI:10.1002/chem.201204428
日期:2013.7.15
fact, their catalytic activity matched those recorded with the free carbenes. Altogether, these results provide strong experimental insight into the mechanism of the Staudinger reaction catalyzed by N‐heterocyclic carbenes. They also highlight the superior catalytic activity of the imidazole‐based carbene IMes compared with its saturated analogue SIMes in the reaction under consideration.
通过用N-甲苯磺酰基苯甲二胺或二苯乙烯酮处理1,3-二甲烯基间苯二酚-2-亚胺(SIMes)或1,3-二甲烯基咪唑-2-亚胺基(IMes)制备了四个两性离子。以高收率分离它们,并通过IR和NMR光谱表征。通过X射线晶体学确定其中三个的分子结构,并通过热重分析监测其热稳定性。咪唑(in)-2-酰胺是非常不稳定的白色固体,没有显示出互变异构成相应的1,2,2-三氨基乙烯衍生物的趋势。他们在N的Staudinger反应中表现出中等的催化活性甲苯磺酰基苯甲二胺与二苯乙烯酮。相比之下,咪唑(2-)ium-烯醇盐是橙红色结晶物质,可以长时间保持稳定。尽管它们具有更高的稳定性,但这些两性离子在仔细研究下仍是模型环加成反应的有效启动子。事实上,它们的催化活性与游离碳烯记录的催化活性相匹配。总之,这些结果为N杂环卡宾催化Staudinger反应的机理提供了强大的实验见解。他们还强调了在考虑的反应中,基于咪唑