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Palladium(0)-catalyzed insertion/annulation sequence between aryl silylethynyl ethers and internal alkynes was found to proceed through activation of ortho-C–H bonds assisted by alkynoxy groups and...

The title reaction of silylethynyl 2,6-(tBu)2phenyl ethers took place in the presence of a palladium catalyst and pivalic acid to give 2-silylmethylenechromanes. The initial products were converted by treatment with acetic acid to thermodynamically stable 4H-chromenes, which were further reacted with activated aldehyde and ketone.

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(0)-catalyzed insertion/annulation sequence between aryl silylethynyl ethers and internal alkynes was found to proceed through activation of ortho-C–H bonds assisted by alkynoxy groups and...

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.

The present reaction proceeds not only for silylated alkynes but also for substrates bearing a carbonaceous substituent.

Silylalkynyl aryl ethers and internal alkynes give under optimized conditions silylmethylidene-substituted chromenes.