REGIOSELECTIVE ALKYLATION OF 4(5)-NITRO-1H-IMIDAZOLES IN ACIDIC MEDIA- STUDY OF TEMPERATURE EFFECTS

Alkylation of 4(5)-nitro-1H-imidatoles in acidic media with reactive a lkylating agents such as bentyl chloride and allyl bromide resulted in the predominant formation of the 5-nitro isomers at lower temperature s (75 degrees C) and the 4-nitro isomers at higher temperatures (140 d egrees C). With less reactive alkylating agents, only the 5-nitro isom ers were produced irrespective of temperature. The mechanism was shown to involve quaternization of the initially formed 1-alkyl-5-nitro-1H- imidazoles followed by preferential dealkylation to yield the thermody namically more stable 4-nitro-1H-imidazoles.