o-Quinonoid compounds. Part III. Benzopyran-3-ones and their salts

Abstract

In boiling acetic anhydride o-formylphenylacetic acid is partly dehydrated to benzopyran-3-one (λmax. 441 nm.), which forms appropriate adducts with dienophiles. In sulphuric acid o-formylphenylacetic acid is completely converted into the conjugate acid of benzopyran-3-one. Experiments leading to 1-methyl-benzopyran-3-one, the more stable 1-phenyl derivative, and their conjugate acids are described.