Azoles .13. Synthesis and bromine->lithium exchange reactions of some 1-substituted 4,5-dibromo-1H-1,2,3-triazoles and 2-substituted 4,5-dibromo-2H-1,2,3-triazoles

4,5-Dibromo-1H-1,2,3-triazole was synthesised by various routes and reacted with chloromethyl methyl ether (N-1/2), methyl chloroformate (N-1), benzyl chloride (N-1), 4-methoxybenzyl chloride (N-1), 4-nitrobenzyl chloride (N-1/2) or triphenylmethyl chloride (N-2) under various conditions, to give isolable products substituted at the N-atoms shown in parentheses. 4,5-Dibromo-1-methoxymethyl-1H- and -2-methoxymethyl-2H-1,2,3-triazole reacted with butyllithium (in diethyl ether or tetrahydrofuran at low temperatures) at position-5 and the resulting lithiated derivatives were quenched with aqueous ammonium chloride, carbon dioxide, methyl chloroformate, benzophenone or dimethyl or diphenyl disulfide to give high yields (71-93%) of the corresponding 5-substituted 1,2,3-triazole, 1-Benzyl-4,5-dibromo-1H-1,2,3-triazole was converted similarly into 1-benzyl-4-bromo-5-methylsulfanyl-1H-1,2,3-triazole (91.5%). In a 'one pot' sequence and through two successive treatments with butyllithium and the appropriate quenching reagent (Ph(2)S(2) and H2O), 4,5-dibromo-2-methoxymethyl-2H-1,2,3-triazole was converted similarly into 2-methoxymethyl-4-phenylsulfanyl-2H-1,2,3-triazole (47% yield).