Ruthenium-Catalyzed Enantioselective Intramolecular Propargylation of Thiophenes with Propargylic Alcohols

Ruthenium-catalyzed enantioselective cyclization of propargylic alcohols bearing a thiophene moiety affords the corresponding propargylated thiophenes in good to high yields with a high enantioselectivity (up to 97% ee). This catalytic reaction is proposed to proceed via chiral ruthenium-allenylidene complexes as key intermediates.