Facile one-pot synthesis of 5-amino-7-aryl-6-cyano-4H-pyrano[3,2-b]pyrroles using supported hydrogen sulfate ionic liquid

摘要

Twelve new derivatives of 5-amino-7-aryl-6-cyano-4H-pyrano[3,2-b]pyrrole were prepared by one-pot acid-catalyzed cyclocondensation reaction of 3-hydroxy-pyrrole, malononitrile, and various aldehydes in the presence of the silica-supported ionic liquid l-methyl-3-(triethoxysilylpropyl)imidazolium hydrogen sulfate as catalyst. The reaction efficiencies were enhanced by moderate electron-withdrawing groups, such CI and Br, on benzal-dehyde, but decreased as substituents became more electron-withdrawing. Among the solvents and catalysts screened for the model reaction, acetonitrile and the silica-supported hydrogen sulfate ionic liquid were found to be the best choices.