Reaction of 2,4-dinitrobenzenediazonium ions with thiophens. Unprecedented coupling to electron-rich methyl groups

Abstract

2,4-Dinitrobenzenediazonium ions couple normally with 2-t-butylthiophen to give the 5-azo-dye, but with 2,3,5-trimethylthiophen and tetramethylthiophen coupling occurs through methyl groups to give the corresponding 24-dinitrophenylhydrazones;2,5-dimethylthiophen gives both the 3-azo-dye and the 2,4-dinitrophenylhydrazone of 5-methylthiophen-2-aldehyde.