Quaternary salts of 2H-imidazoles

Abstract

Treatment of the 4,5-diphenyl-2H-imidazoles (1a–e) with alkyl iodides gives novel 1H⁺,2H-imidazolium salts (2) and (3). The metho-salt (2)N-methyl protons are readily exchanged for deuterium, and anions formed by the action of base give, with m-chlorobenzaldehyde, 2,3,5,7a-tetrahydroimidazo[5,1-b]-oxazoles (4), hydrolysable in acid to 2-(3-chlorophenyl)-2-hydroxyethylamine (6). Borohydride reduction of the metho-salt (2a) gave a dihydro-1H-imidazole (7) which with acid yielded 2-methylamino-1,2-diphenylethanone (8), and with methyl iodide a metho-salt (10). Direct (peracid) oxidation of 2H-imidazoles to N,N′-dioxides is reported for the first time.