Lithium Benzocyclobuteneoxide as a Precursor of a Vinylogous Enolate: Solvent‐Controlled Synthesis of Highly Functionalized Seven‐Membered Benzocarbocycles

The reaction of alkynyl Fischer carbene complexes with the ortho-quinodimethane obtained from lithium benzocyclobuteneoxide leads to the preparation of highly functionalized seven-membered benzocarbocycles (see scheme). The position and the nature of the functional groups in the product are solvent controlled: benzocycloheptenones are selectively formed in THF, whereas benzocycloheptene ketals are exclusively synthesized in diethyl ether.