Synthesis of naphthalene derivatives through platinum(II)-catalyzed reaction of 2-alkynylbenzoates with vinyl ethers

A concise method for the preparation of 1-acyl-4-alkoxy- or 1-acyl-4-alkylsulfanylnaphthalenes has been developed by the PtCl2-catalyzed reaction of o-ethynylbenzoates or benzothioates with vinyl ethers. Treatment of o-alkynylbenzoate derivatives with PtCl, generated the platinum(II)-containing carbonyl ylides as a key reactive intermediate and these species reacted with vinyl ethers to give substituted naphthalenes in good yields. The presence of the platinum-containing carbonyl ylide was confirmed by NMR analyses of the mixture of o-ethynylbenzoate and [PtCl2(H2C=CH2)](2). Furthermore, it was suggested that the naphthalene derivatives were produced by [3+2] cycloaddition of the ylide species with vinyl ethers, followed by 1,2-alkyl migration of the generated platinum-carbene intermediates.