Products from the Nitration of 2,5-Dimethylthiophene and Its 3,4-Dibromo Derivative. Two Modes of the Formation of Dithienylmethanes

Article abstract of DOI:10.1246/bcsj.54.771

The reaction of 2,5-dimethylthiophene with copper(II) nitrate in acetic anhydride gave 3-nitro-2,5-dimethylthiophene and 2,5-dimethyl-3-(5-methyl-2-thenyl)thiophene as major isolable products.The treatment of 3,4-dibromo-2,5-dimethylthiophene with nitric acid (d=1.5) in dichloromethane in the presence of a catalytic amount of sulfuric acid afforded 3,4-dibromo-5-methyl-2-(nitrooxymethyl)thiophene, which, on thin-layer chromatography over silica gel using hexane as the eluant, underwent a partial novel coupling reeaction through the loss of one of one methylene carbon atom, thus giving 3,3',4,4'-terabromo-5,5'-dimethyl-2-thienylmethane along with the expected 3,4-dibromo-2-hydroxymethyl-5-methylthiophene and bis(3,4-dibromo-5-methyl-2-thenyl) ether.