Preparation and reactions of bromo-2-nitro- and bromo-2-aminoimidazoles

Abstract

Can. J. Chem. 71,427 (1993). Treatment of 1-methyl-2-nitroimidazole with bromine in water resulted in rapid dibromination to give 4,5-dibromo-1-methyl-2-nitroimidazole. In dioxane, the bromination was slower, and could be controlled to give 4-bromo-1-methyl-2-nitroimidazole 5 and 5-bromo-1-methyl-2-nitroimidazole 6 in a 4 : 1 ratio. In an attempt to displace the bromine, the monobromo compounds were treated with cysteamine hydrochloride. In each case the nitro group was displaced instead, the 4-bromo 5 resulting in 2-[(2-aminoethyl)thio]-4-bromo-1-methylimidazole 9 as sole product, and the 5-bromo 6 giving two products identified as the monosubstituted 2-[(2-aminoethyl)thio]-5-bromo-1-methylimidazole 13 and the disubstituted 2,5-bis[2-(aminoethyl)thio]-1-methylimidazole 12. The latter product forms by further reaction of the former and was the sole material observed at long reaction times. A fraction of 12 may also originate from an initial displacement of bromine giving 5-[(2-aminoethy1)thiol-1-methyl-2-nitroimidazole 14, although this cannot be observed due to a rapid further displacement of its nitro group. The bromonitroimidazoles 5 and 6 were reduced to 4-bromo-2-amino-1-methylimidazole 25 and 5-bromo-2-amino-1-methylimidazole 26 with Zn/HCl. On reflux in water, in the presence or absence of cysteamine hydrochloride, these undergo a protodebromination resulting in the same product, 2-amino-1-methylimidazole 17. In D20 the 4-bromo isomer was demonstrated to react specifically to give 2-amino-4-deuterio-1-methylimidazole 27. Attempted preparation of the bromoaminoimidazoles 25 and 26 by bromination of 2-amino-1-methylimidazole in water resulted in the clean formation of cis and trarzs 2-amino-4,5-dihydro-4,5-dihydroxyimidazolium ions 18. SALIM F. FARAH et ROBERT A. MCCLELLAND. Can. J. Chem. 71, 427 (1993) Le traitement du 1-methyl-2-nitroimidazole avec du brome dans l'eau conduit a une dibromation rapide, avec formation du 4,5-dibromo-1-methyl-2-nitroimidazole. Dans le dioxane, la bromation est plus lente et elle peut &tre contr6lCe pour conduire a la formation des 4-bromo-(5) et 5-bromo-(6) 1-methyl-2-nitroimidazoles, dans un rapport de 4 : 1. Dans un effort pour deplacer le brome, on a trait6 les composCs monobromes avec de chlorhydrate de la cystkinamine. Dans chaque cas, c'est plut6t le groupe nitro qui a Ct C deplace; le derive 4-brome (5) conduit uniquement au 2-[(2-aminoCthy1)thiol-4-bromo-1-methylimidazole (9) alors que le compose 5-bromC (6) fournit deux produits identifies comme le 2-[(2-aminotthy1)thiol-5-bromo-1-methylimidazole (13) monosubstituC et le 2,5-bis-[2-(aminoCthy1)thiol-1-methylimidazole (12) disubstitue. Ce dernier compose se forme par reaction ulterieure du premier; il est le seul produit a se former aprits des temps de reactions prolonges. Une partie du compose 12 peut aussi provenir d'un deplacement initial du brome conduisant au 5-[(2-aminoethyl)thio]-1-methyl-2-imidazole (14); toutefois, on ne peut pas observer sa formation a cause de la substitution rapide du groupe nitro. On...

Synthesis of 5-Amino-1,2,4-Triazole-3-One Through the Nitroreduction of 5-Nitro-1,2,4-Triazole-3-One. Comparison Between Chemical and Microbiological Catalysis

“…This reaction is generally accomplished by various reducing agents, including metals in acidic conditions (Farah, 1992;Griffin et al, 1989;Bellamy, 1984), hydrides (Petrini, 1987;Osby, 1985;Hanaya et al, 1979) or catalytic hydrogenation (Chipen, 1966;A1 Shaar et al, 1992;Rampulla, 1986). Most of these methods are unsuitable when the starting nitrocompound bears sensitive functional groups, as they lead to unwanted side reactions or low yields (Buehler, 1970).…”