Carbene Reactivity of 4-Diazo-4H-imidazoles toward Nucleophiles and Aromatic Compounds
journal contributionposted on 18.12.2009 by Matthew R. Smith, Alexander J. Blake, Christopher J. Hayes, Malcolm F. G. Stevens, Christopher J. Moody
Any type of content formally published in an academic journal, usually following a peer-review process.
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.