One‐Pot Copper‐Catalyzed Cascade Bicyclization Strategy for Synthesis of 2‐(1H‐Indol‐1‐yl)‐4,5‐dihydrothiazoles and 2‐(1H‐Indol‐1‐yl)thiazol‐5‐yl Aryl Ketones with Molecular Oxygen as an Oxygen Source

Abstract

AbstractAn atom‐economical method for synthesizing N‐heterocyclic indoles from readily available o‐alkynylphenyl isothiocyanates and propargylamine derivatives is reported. This method involves a copper‐catalyzed cascade bicyclization process consisting of an intramolecular 5‐exo‐dig hydrothiolation reaction and an intramolecular hydroamination reaction and, depending on whether or not molecular oxygen is present, selectively affords Z‐isomers of 2‐(1H‐indol‐1‐yl)‐4,5‐dihydrothiazoles or 2‐(1H‐indol‐1‐yl)thiazol‐5‐yl aryl ketones in satisfactory yields. Mechanistic studies indicate that molecular oxygen acts as the oxygen source for the ketone moiety in the products.magnified image