Recyclable Indium(III) Chloride Catalyzed Site-Selective Double Substitution in One Pot for the Synthesis of Isatin N-Ribonucleosides under Microwave Irradiation

A novel one-pot synthesis of isatin N-ribonucleosides from N-phenylribosylamines and diethyl oxalate in ethanol catalyzed by recyclable indium(III) chloride under microwave irradiation has been developed. The transformation consists of indium(III) chloride catalyzed nucleophilic substitution by N-phenylribosylamines on diethyl oxalate followed by rapid intramolecular electrophilic substitution, which results in annulation of a five-membered nitrogen heterocycle on to the benzene ring yielding isatin N-ribonucleosides. The reaction proceeded smoothly in quantitative yields at ambient temperatures. The starting materials, N-phenylribosylamines, were prepared by indium(III) chloride catalyzed nucleophilic substitution of the anomeric hydroxy group of beta-D-ribofuranose by an arylamine under microwave irradiation.