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，与在良好的氢供体溶剂中的还原反应竞争。二氯甲烷与反应生成相应的4-氯咪唑。芳烃是咪唑亚基卡宾的优异捕获剂，可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基卡宾形成的第一个吡啶基亚胺8的实例，而六氟苯中的辐照则生成咪唑氮杂环辛烷11，推测是通过一个初始的诺卡二烯中间体实现的。