Acetylenic Acids. I. The reaction of arylpropiolic acids with carbodiimides

The formation of substituted 1-phenylnaphthalene-2,3-dicarboxylic anhydrides from substituted phenylpropiolic acids by carbodiimides is shown to be a general reaction and proceeds in high yields under mild conditions. Heterocyclic acetylenic acids also form analogous products in high yield. The reaction is confined to α,β-acetylenic acids conjugated with an aromatic ring, as alkylpropiolic acids form mixtures of alkylpropiolic anhydrides and N-acylureas under the same conditions and esters of arylpropiolic acids do not react. The effects of temperature, bases, and solvents on the reaction are described. Some features of the nuclear magnetic resonance spectra of the 1- phenylnaphthalene products are discussed.