Synthesis of functionalized 3-aryl-3H-benzofuranone derivatives from aryl acetate via [3 + 2] annulation of 1,4-dihydroxy-2-naphthoic acid ester.

A novel [3 + 2] cascade reaction of aryl acetate with 1,4-dihydroxy-2-naphthoic acid ester by cooperative catalysis of isothiourea and vanadium is developed. The key step of the reaction is that the C1-ammonium enolates generated from aryl acetate will cycloadduct to 1,4-naphthoquinone intermediates. 3-Aryl-3H-benzofuranone derivatives can be prepared in medium to good yields under mild conditions.