The Carboxylation of Phenol Derivatives. IV.

Synthesis of p-Hydroxybenzoic Acid and Salicylic Acid from Alkaliphenoxides in N, N-Dimethylformamide (2).

Abstract

In the previous paper, the reactions of alkali phenoxide and carbon dioxide gasin N, N-dimethylformamide (DMF), an aprotic polar solvent, under the atmosphericpressure were reported. In the present study, a similar reaction was carried out under higher carbon dioxide pressure and temperatures. The yields of salicylic acid (SA) and 4-hydroxyisophthalic acid (4-OIP) were markedly improved, whereas that of p-hydroxybenzoic acid (PUB) decreased with higher reaction temperature and longer reaction time, thus resulting in a slight increase in the yield of total hydroxy acids. The stability of POB and SA alkali salts in DMF at high reaction temperatures were also examined. Evolution of carbon dioxide was noted, and SA and a small amount of 4-OIP were obtained. These results resemble with that obtained by using alkali phenoxides as reported in the first half of this report.