脒类化合物在构筑含氮杂环骨架中的应用进展

Application Progress of Amidine Compounds in Construction of Nitrogen-Containing Heterocyclic Skeletons

脒类化合物是一种重要的有机合成砌块,由于其具有反应活性高且廉价易得,利用脒作为起始原料来构建各类骨架新颖的含氮杂环受到了有机化学家的持续关注,多种类型的杂环化合物(如嘧啶,喹啉,喹唑啉和三嗪等)的合成都得以有效实现,这也极大地丰富了过渡金属催化以及串联环化反应研究。聚焦于脒类这一多功能化合物在氮杂环合成中的应用,主要从无过渡金属体系下的串联环化反应以及自由基型环化反应两个角度来展开综述,并着重对相应的反应策略和机理进行了详细阐述,同时进一步从绿色合成化学发展角度指出光电媒介下脒盐相关的自由基反应具有广阔的发展前景。

Amidines are an essential building block in organic synthesis.Due to their high reactivity,low-price and easy preparation,using amidines as starting materials for the construction of various novel nitrogen-containing heterocyclic compounds has attracted sustained attention from organic chemists.Thus the synthesis of various heterocyclic compounds(pyrimidine,quinoline,quinazoline and triazine,etc)has been effectively realized,which has greatly enriched the research field of transition metal catalysis and tandem cyclization.This review focuses on the tandem cyclization reactions related to amidine compounds,mainly including transition metal-free systems and free radical-based cyclization reactions with particular emphasis on reaction strategies and mechanisms.At the same time,from the perspective of the development of green synthetic chemistry,it is pointed out that the radical reactions involving amidine salts driven by visible light or electricity have broad development prospects.