4- and 5-Trifluoromethylimidazoles. Novel Cyclization of Trifluoroacetylated Aldehyde Dimethylhydrazones
Thermally induced cyclization reaction of trifluoroacetylated arylaldehyde dimethylhydrazones 1 in refluxing toluene afforded 1-methyl-4-aryl-5-trifluoromethylimidazoles 2 in good yields.In contrast thermal cyclization of 1 in the presence of silica gel gave regioisomeric 1-methyl-4-trifluoromethyl-5-aryl-imidazoles 5 as major products.These reactions could be extended to the synthesis of related several 1,4,5-trisubstituted imidazoles.