The paper describes synthesis of two regioisomeric 2-amino-3-formyl and 3-amino-2-formyl substituted derivatives of tetrahydrobenzo[b] thiophene and their preparation for subsequent thermally-initiated reactions with secondary amines for generation of azomethine ylides; these azomethine ylides entered into intramolecular 1,3-dipolar cycloadditions. In this way, two series of new fused heterocyclic compounds were prepared, having three stereogenic centres. The compounds were identified and their structures determined.