Synthesis and Trapping of 4H- and 5H-Thieno(3,4-c)pyrroles.

The synthesis and trapping of the parent compound and derivatives of the thieno[3,4-c]pyrrole ring system are reported. Intramolecular 1, 3-dipolar cycloaddition of the azides 9a–d and subsequent acid-catalysed 1,3-dipolar cycloreversion of the thienopyrrolotriazoles 10a–d afforded the parent compound 3a and its derivatives 3b–d. Trapping of 3a–d by 1,3-dipolar cycloaddition with N-phenylmaleimide via the azomethine ylide 2a–d gave cycloadducts 14a–d and 15a–d. Reactions of the halides 8a, c, d and g with benzylamine produced N-benzylazomethine glides 18a, c, d and g which were also trapped by N-phenylmaleimide to give the cycloadducts 19a, c, d and g.