The unique regioselectivity in the formation of disubstituted-1,4-benzoquinones generated from the reaction of 4-hydroxycoumarins with 1,4-benzoquinone

The 2,3-disubstituted 1,4-benzoquinones were synthesized through the regioselective addition of 4-hydroxycoumarins with 1,4-benzoquinone in aqueous acetone, which were different from 2,5-disubstituted adducts generated by the previously reported reaction of compounds possessing an activated methylene with 1,4-benzoquinone.