Cobalt and iron metallates as catalysts for cyclization reactions of diynes and triynes: [2+2+2] Cycloaddition vs. Garratt-Braverman reaction

Abstract

Highly reduced anthracene and naphthalene cobaltates and ferrates catalyze the cyclization of diynes and triynes, furnishing expected [2 + 2 + 2] cycloaddition products as well as unexpected annulation products from Garratt-Braverman cyclization reactions. The anionic Cp*Fe-naphthalene complex exclusively catalyzes the latter reaction. The Garratt-Braverman reactions show a large solvent-dependent substrate conversion. Diynes and triynes afforded the corresponding substituted 1,3-dihydronaphthofurane products with yields up to 91% isolated yield.