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4-二氮咪唑羧酸盐衍生的卡宾，在热或光化学条件下，与醇和胺分别发生O-H和N-H插入反应，产率适中，在与良好氢供体溶剂中还原反应的竞争中。二氯甲烷反应生成相应的4-氯咪唑。芳烃是咪唑亚甲基卡宾的优异捕获剂，导致一系列芳基咪唑衍生物7的生成。与吡啶的反应产生了由咪唑亚甲基卡宾形成的第一个吡啶鎓亚胺8的例子，而在六氟苯中的照射则产生了咪唑氮杂环辛烷11，据推测是通过初始的诺卡烯中间体实现的。