Carbene Reactivity of 4-Diazo-4H-imidazoles toward Nucleophiles and Aromatic Compounds

Carbenes derived from diazoimidazolecarboxylates 4 under thermal or photochemical conditions undergo O−H and N−H insertion reactions with alcohols and amines, respectively, in moderate yield, in competition with reduction in good H-donor solvents. Dichloromethane reacts to give the corresponding 4-chloroimidazole. Aromatic hydrocarbons are excellent traps for the imidazolylidene carbene and lead to a range of arylimidazole derivatives 7. Reaction with pyridine leads to the first example of a pyridinium ylide 8 formed from an imidazolylidene carbene, whereas irradiation in hexafluorobenzene gives the imidazoazocine 11, presumably by way of an initial norcaradiene intermediate.

由4-二唑咪唑羧酸盐衍生的碳烯在热或光化学条件下，分别与醇和胺发生O-H和N-H插入反应，产率适中，在良好的氢供体溶剂中与还原反应相竞争。二氯甲烷反应生成相应的4-氯咪唑。芳烃是咪唑亚甲基碳烯的优良捕获剂，从而得到一系列的芳基咪唑衍生物7。与吡啶的反应产生了第一个由咪唑亚甲基碳烯形成的吡啶鎓叶立德8的例子，而在六氟苯中的辐照则生成咪唑亚胺11，推测是通过初始的诺卡雷达烯中间体实现的。