A novel approach to 4H-thieno[3,2-b]pyrroles

The condensation of 3-nitro-5-carboxy-2-methylthiophene with acetals of amides proceeds smoothly, and further ammonium formate– Pd/C reduction of nitroenamines thus obtained affords 2-carboxythieno-(5-R)-[3,2-b]pyrroles (R = H, Me) in good yields.