Reactions of 2-unsubstituted 1H-imidazole 3-oxides with 2,2-bis(trifluoromethyl)ethene-1,1-dicarbonitrile: A stepwise 1,3-dipolar cycloaddition

The reaction of 1,4,5-trisubstituted 1H-imidazole-3-oxides I with 2,2-bis(trifluoromethyl)ethene-1,1dicarbonitrile (7, BTF) yielded the corresponding 1.3-dihydro-2H-imidazol-2-ones 10 and 2-(1,3-dihydro-2H-imidazol-2-ylidene)malononitriles 11, respectively, depending on the solvent used. In one example, a 1: 1 complex, 12, of the 1H-imidazole 3-oxide and hexafluoroacetone hydrate was isolated as a second product. The formation of the products is explained by a stepwise 1,3-dipolar cycloaddition and subsequent fragmentation. The structures of 11d and 12 were established by X-ray crystallography.