Lewis acid-catalyzed divergent synthesis of polysubstituted furans and pyrroles†

The development of an advisable strategy to obtain biologically relevant polysubstituted furans and pyrroles is a highly anticipated yet challenging task. Here we report an efficient synthetic strategy for the rapid construction of multisubstituted C2-furan or pyrrole carboxylic acid derivatives via a cascade reaction from simple and readily available starting materials. This catalytic protocol, characterized by inexpensive Lewis catalysts and high atom economy, provides access to a wide variety of tri-, and tetrasubstituted furan/pyrrole derivatives in excellent yields. Gram-scale synthesis and synthetic applications are demonstrated.