The reaction of 1,4,5-trisubstituted 1H-imidazole-3-oxides 1 with 2,2-bis(trifluoromethyl)ethene-1,1-dicarbonitrile (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
The reaction of 1,4,5-trisubstituted 1H-imidazole 3-oxides 1 with Ac2O in CH2Cl2 at 0-5 degrees leads to the corresponding 1,3-dihydro-2H-imidazol-2-ones 4 in good yields. In refluxing Ac2O, the N-oxides 1 are transformed to N-acetylated 1,3-dihydro-2H-imidazol-2-ones 5. The proposed mechanisms for these reactions are analogous to those for N-oxides of 6-membered heterocycles (Scheme 2). A smooth synthesis of 1H-imidazole-2-carbonitriles 2 starting with 1 is achieved by treatment with trimethylsilanecarbonitrile (Me2SiCN) in CH2Cl2 at 0-5 degrees (Scheme 3).