Melamine trisulfonic acid: A new, efficient and reusable catalyst for the synthesis of some fused pyranopyrrole derivatives

Synthesis of a new series of 5-amino-7-aryl-6-cyano-4H-pyrano[3,2-b]pyrrole derivatives has been reported. The cyclocondensation synthesis proceeded by the one-pot reaction of 3-hydroxypyrrole, malononitrile and various aromatic aldehydes in the presence of melamine trisulfonic acid (MTSA). The process presented here is operationally simple, environmentally benign and has excellent yield. Furthermore, the catalyst can be recovered conveniently and reused efficiently.