Thermal or Lewis acid-promoted electrocyclisation and hetero Diels–Alder cycloaddition of α,β-unsaturated (conjugated) carbodiimides: a facile synthesis of nitrogen-containing heterocycles
作者:Takao Saito、Takahiro Ohkubo、Hideki Kuboki、Masayuki Maeda、Kensaku Tsuda、Takayuki Karakasa、Sadayoshi Satsumabayashi
DOI:10.1039/a805574b
日期:——
β-styrylcarbodiimide was entirely unreactive toward either the electrocyclisation or the Diels–Alder reaction even under severe reaction conditions. 4-Coumarylcarbodiimide underwent an inverse electron-demand Diels–Alder reaction with an enamine either thermally or in the presence of a Lewis acid catalyst to afford chromenopyridines. Thus experimentally observed reactivity differences of the substituted
由亚氨基膦酸酯与异氰酸酯的aza-Wittig反应制得的α,β-二芳基乙烯基-和α-苯乙烯基-碳二亚胺在加热或路易斯酸促进的条件下,通过适当的亲二烯体在加热或路易斯酸促进的条件下进行6π-电环化或Diels-Alder反应。作为四氰基乙烯,乙炔二甲酸二甲酯,马来酰亚胺,丙酸乙酯和异氰酸甲苯磺酯,得到异喹啉,吡啶,恶嗪,嘧啶和吡咯并吡啶。相反,即使在严格的反应条件下,β-苯乙烯基碳二亚胺对电环化或Diels-Alder反应也完全不反应。4-Coumarylcarbodiimide通过烯胺加热或在路易斯酸催化剂存在下与烯胺进行逆电子需求的Diels-Alder反应,得到苯并吡啶。