4H-thieno[3,4-c]pyrrole: synthesis and characterization of the parent ring system

4H-Thieno[3,4-c]pyrrole (4) was synthesised from the azide (8) by intramolecular 1,3-dipolar cycloaddition followed by acid-catalysed 1,3-dipolar cycloreversion of the dihydrotriazole intermediate (9); the crystal structure of one of the products formed on trapping (4) with N-phenylmaleimide has been determined.