Selective synthesis of 2-(5-oxo-1-arylhex-1-yn-3-yl)phenyl benzoates via FeCl3-mediated cascade reactions of propargylamines with beta-enamino ketones

A mild and efficient FeCl3-mediated cascade reaction of ortho-hydroxyl propargylamines with beta-enamino ketones has been developed. This protocol provided a practical and selective method to synthesize 2-(5-oxo-1-arylhex-1-yn-3-yl)phenyl benzoates via in situ generated alkynyl o-quinone methides following a cascade intermolecular 1,4-conjugate addition/intramolecular nucleophilic addition/reverse Claisen condensation/hydrolysis pathway. Furthermore, a series of 2-(3-oxo-1-arylbutyl)phenyl benzoates with good functional group tolerance were prepared in good to high yields under these reaction conditions.