Annulation of Alkynyl Aryl Ethers with Allyl Pivalates To Give 2,3-Bismethylenechromanes through Double C−H Bond Cleavage

The treatment of silylethynyloxyarenes with allylic pivalates in the presence of a palladium catalyst led to efficient C−H bond cleavage in both substrates and a novel annulation reaction to give 2,3‐bismethylenechromanes. When ortho‐allylated silylethynyloxybenzenes were used as the substrates, the same products were obtained. This result shows that site‐selective intramolecular hydrovinylation is involved in the annulation reaction. The synthetic utility of the products was demonstrated by the construction of condensed polycycles. Doppelt oder nichts: Benzopyrane mit Bis(exomethylen)‐Substitution wurden durch zwei C‐H‐Spaltungen erhalten: 1) intermolekulare Kupplung von Alkinylarylethern mit allylischen Pivalaten in ortho‐Stellung und 2) intramolekulare Hydrovinylierung der ortho‐allylierten Alkinylarylether. Die Produkte ermöglichen die einfache Synthese von linear kondensierten multifunktionellen Oxacyclen (siehe Schema).