Catalyst activity in alkylthiophene dealkylation

The transformations of 2-alkylthiophenes on various catalysts were studied. In the presence of oxide and sulfide catalysts, 2-methylthiophenes and 2-isopropylthiophenes underwent dealkylation to thiophene. The reaction was complicated by isomerization to 3-alkylthiophene and cracking. The dealkylation of 2-ethylthiophene occurred only in the presence of oxide catalysts. Side-chain dehydrogenation resulting in the formation of 2-vinylthiophene primarily occurred under the action of sulfide and some oxide catalysts. Acid catalysts (amorphous aluminosilicate and zeolites in the form of hydrogen) were the most active and selective in the dealkylation of 2-alkylthiophenes. It is believed that the dealkylation reaction of 2-alkylthiophenes on these catalysts occurs by means of a protolytic mechanism. © 2005 MAIK "Nauka/ Interperiodica".