Palladium catalysis in the construction of the benzo[b]furan and furan rings from alkynes and organic halides or triflates

Three general processes leading to the construction of functionalized benzo[b]furan and furan rings are reviewed: 1) the coupling-cyclization methodology, involving the palladium-catalyzed coupling of terminal alkynes with o-iodophenols, or the alternative palladium-catalyzed coupling of terminal alkynes containing proximate oxygen nucleophiles with aryl and vinyl halides or triflates, followed by the cyclization of the resultant coupling intermediates; 2) the oxypalladation-reductive elimination domino reaction, based on the trans addition of the oxygen and an organopalladium complex across the carbon-carbon triple bond, followed by a reductive elimination step; 3) the carbopalladation-cyclization reaction, based on the syn addition of an organopalladium complex, containing an oxygen nucleophile, to the carbon-carbon triple bond, followed by the cyclization of the resultant carbopalladation adduct.