A facile route to 4,5,6,7-tetrahydrothiophenes and benzothiophenes

2-Substituted tetrahydro- and cyclopentathiophenes 2 were produced in high yields by treatment of the semi-cyclic trisubstituted 1,4-diketones 1 such as 2-phenacylcyclohexan-1-one, 2-acetonylcyclohexan-1-one, and 2-phenacylcyclopentan-1-one, with Lawesson's reagent.