Condensations of benzil with phenols and aryl ethers mediated by tin(IV) chloride pentahydrate

The reaction of benzil with phenol at 180°C in the presence of SnCl4·5H2O produces a benzofuran, a benzofuranol, a benzodifuran, and a benzofuranone. Anhydrous tin(IV) chloride also gives a benzofuranofuranone. Other phenols and their methyl ethers yield related products. The good yields of the benzo- and naphtho-furanones make the method an attractive alternative to the benzilic acid route to such compounds.