Chloromethylation of 2,5-dimethylthiophene

Abstract

1. A study was made of the chloromethylation of 2,5-dimethylthiophene with a mixture of formaldehyde and hydrochloric acid and with chloromethyl methyl ether. The presence of the compound of m.p. 72* described by Buu-Hoi and Hoan could not be detected among the reaction products. 2. In the chloromethylation of 2,5-dimethylthiophene in presence of zinc chloride, compounds were formed which corresponded in composition to 3,3′-methylenebis[2,5-dimethylthiophene] and 3,4-bis(2,5-dimethyl-3-thenyl)-2,5-dimethylthiophene. These compounds were obtained also when 2,5-dimethylthiophene reacted with 3-(chloromethyl)-2,5-dimethylthiophene in presence of aluminum chloride and when 2,5-dimethylthiophene reacted with 2,5-dimethyl-3-thiphenemethanol in presence of sulfuric acid. 3. The compound of m.p. 43.5° was obtained also by the reduction of bis (2,5-dimethyl-3-thienyl) ketone. 4. By the chloromethylation of 2,5-diethylthiophene and of 2,5-di-tert-butylthiophene under selected conditions, the corresponding dialkylbischloromethylthiphenes were obtained. The formation of substituted methylenedithiophenes was not observed under these conditions.