Iodine-Catalyzed Regioselective Synthesis of Multisubstiuted Pyrrole Polyheterocycles Free from Rotamers and Keto-Enol Tautomers.

A highly regioselective iodine-mediated cascade reaction for the synthesis of multifunctional polyheterocyclic systems is developed by employing 3-(2-oxo-2-arylethylidene)oxindoles and 1,4-benzoxazinone as starting materials. The polyheterocycles are skillfully embraced with oxindole, pyrrole, and coumarin scaffolds, which are well-known for their enriched biological activity. The current approach worked under mild reaction conditions. The reaction afforded a single product, and no rotameric and keto-enol isomeric products are formed. The method is environmentally benign and atom-economical, and the only side product of this reaction is water. This protocol obviates the purification techniques such as column chromatography for the isolation of the products. The products were isolated by decantation of the solvent or by recrystallization. The reaction proceeds through inter- and intramolecular C-C and C-N bond formation.