Palladium-catalyzed sequential oxidative cyclization/coupling of 2-alkynylphenols and alkenes: a direct entry into 3-alkenylbenzofurans.

A new Pd-catalyzed tandem intramolecular oxypalladation/Heck-type coupling between 2-alkynylphenols and alkenes is reported, leading to 3-(1-alkenyl)benzofurans. Participating alkenes include those substituted with an electron-withdrawing group (ester, ketone, amide, nitrile, sulfone), as well as styrene. Remarkably, beta-substituted-alpha,beta-unsaturated carbonyl-type derivatives also participate effectively. The ready availability of substituted alkynylphenols, together with flexibility in the alkene choice, makes this simple strategy a versatile one for the synthesis of structurally diverse benzofuran derivatives.