C-5 functionalization of trisubstituted imidazoles with azodicarbonyl compounds

Article abstract of DOI:10.1002/jhet.5570330107

Certain 1,2,4-trisubstituted imidazoles underwent electrophilic attack of azodicarbonyl compounds on the 5-position to form 5-(1,2-dialkoxycarbonyl)hydrazino- and 5-(4-phenyl-3,5-dioxo-1,2,4-triazolidin-1 yl)imidazole derivatives in moderate to high yields. The reaction was highly susceptible to the nature and the substitution pattern of the substituents on the imidazole ring. Thus 1,4-di- or 1,2,5-trisubstitued imidazoles, and 2-methylsulfinylimidazoles gave no reaction. Reductive cleavage of the tetrasubstituted imidazoles with zinc dust-acid gave the 1- or 1,2-cleaved product depending upon the reaction temperature, but the hydrazino moiety remained intact.