Palladium-catalyzed annulation of allenes using functionally substituted vinylic halides

Palladium catalyzes the regio-and stereoselective annulation of allenes by vinylic halides bearing alcohol-, amine-, sulfonamide-, carboxylic acid-, carboxamide-and carbanion-stabilizing groups to produce a variety of five-and six-membered-ring unsaturated heterocycles and carbocycles. The reaction appears to proceed by vinylic palladium formation and addition to the allene, followed by intramolecular nucleophilic displacement of the palladium. Six-membered rings are formed more readily than five-membered rings. The regioselectivity is generally high, with vinylic halides bearing alcohol, carboxylic acid, or carboxamide groups affording predominantly the product of intramolecular attack on the more substituted end of the pi-allylpalladium intermediate, while amines and carbanions attack quite selectively at the less substituted end of the pi-allylpalladium intermediate. Vinylic halides bearing tosylamides afford mixtures of regioisomers, where the predominant six-membered ring product arises by attack on the less substituted end of the allene, while the major five-membered ring products involve addition to the more substituted end of the allene.