Naphthalenes, isoquinolines, and a benzazocine from zirconocene - Copper-mediated coupling of benzocyclobutadiene with nitriles and alkynes

Commercially available 1-bromobenzocyclobutene is a potentially useful synthon particularly with the application of organometallic methodology. Here we show that it is readily converted into Cp2Zr(benzocyclobutadiene), which couples with alkynes or nitriles giving five-membered zirconacycles. Treatment of these alkyne- or nitrile-derived zirconacycles with CuCl yields substituted naphthalenes, isoquinolines, or in the presence of MeO2C-CC-CO2Me, a 2-benzazocine containing an eight-membered ring.