CARBOXYLATION OF HYDROXYARENES WITH POTASSIUM ETHYL CARBONATE

Аннотация

The influence of the conditions for carrying out the carboxylation reaction of phenol and its
derivatives (petrochemical products) with alkaline salts of alkylcarbonic acids (potassium ethyl carbonate), easily
synthesized from carbon dioxide, alcohols and alkaline metal hydroxides, was studied in order to develop new,
effective methods for producing practically valuable p-hydroxybenzoic acid and other hydroxybenzoic acids (a class
of compounds having a wide range of biologically active properties and other beneficial properties) is relevant and
timely. A new simple and convenient method for the synthesis of p-hydroxybenzoic acid by the reaction of phenol
carboxylation with potassium ethyl carbonate has been developed, which allows one to obtain the target product
without impurity of o-hydroxybenzoic acid. For the first time, optimal conditions were found for the regioselective pcarboxylation of phenol (pressure of carbon dioxide, temperature and duration of the process) under which the yield
of p-hydroxybenzoic acid is 71,0%, and the effect of various substituents in the aromatic ring on the yield of the
target products of the carboxylation of phenol derivatives is determined sodium and potassium carbonates. The
influence of the nature of the alkyl groups of potassium alkyl carbonates on the carboxylation activity of the latter in
the phenol carboxylation reaction was determined. We have studied that temperature has a strong influence on the
direction of phenol carboxylation. When carrying out the reaction below 200°C, carboxylation proceeds to the o- and
p-positions with the formation of o-hydroxybenzoic and p- hydroxybenzoic acids; the o-isomer predominates (44,9-
66,7%). When carrying out the reaction above 200°C, only p-hydroxybenzoic acid is formed without an impurity of
o-hydroxybenzoic acid.