Novel Synthetic Route to Pyrano[2,3-b]pyrrole Derivatives

Synthesis of a new series of 2-amino-4,7-dihydro-4-arylpyrano[2,3-b]pyrrole-3-carbonitrile has been reported. The acid-catalyzed cyclocondensation synthesis proceeded by the one-pot reaction of 2-hydroxypyrrole, malononitrile, and various aromatic aldehydes in the presence of silica-supported ionic liquid of [pmim]HSO4 (SiO2) (silica-supported 1-methyl-3-(triethoxysilylpropyl)imidazolium hydrogensulfate) as an efficient catalyst. The electronic nature of the substitution attached to the aldehyde affected the reaction efficiency profoundly.