Palladium-catalyzed hydrobenzylation of ortho-tolyl alkynyl ethers by benzylic C-H activation: remarkable alkynoxy-directing effect.

It's selective: The title reaction involves palladium(0)-catalyzed insertion of C≡C bonds into benzylic C(sp(3))-H bonds, thus providing efficient access to 2-methylene-2,3-dihydrobenzofurans, which transform into benzofurans upon treatment with a weak acid (e.g., AcOH) and electrophiles. The alkynoxy group serves as a directing group in promoting C-H bond functionalization.

Palladium-catalyzed cycloaddition of alkynyl aryl ethers with internal alkynes via selective ortho C-H activation.

Alkynyl aryl ethers react with internal alkynes through selective ortho C-H activation by a palladium(0) catalyst to give substituted 2-methylidene-2H-chromenes. The alkynoxy group acts as a directing group to promote ortho C-H functionalization. Deuterium-labeling experiments indicated that the arylpalladium hydride complex is a key intermediate via oxidative addition. Various functional groups tolerate the present transformation to give the corresponding products.