Heterogeneous palladium multi-task catalyst for sequential Heck-reduction–cyclization (HRC) reactions: influence of the support

An evaluation study of various palladium supports led to the selection of charcoal as the most efficient system for the preparation of oxindoles by sequential Heck-reduction–cyclization (HRC) reactions. The in situ prepared Pd0/C was not recyclable for further cross-coupling reactions but remains still highly active for reduction processes. The sustainable chemistry described herein allows extremely simple experimental protocol under mild conditions, free of any base, ligand and additive.