Aim and Objective: The carboxylation of organoboronic esters with CO2 is an attractive way of preparing
the functionalized carboxylic acid derivatives. For the silver-catalyzed carboxylation of arylboronic esters
with CO2, sensibility of catalytic system to CO2 pressure resulted in a high CO2 pressure required in the
reaction. This work focuses on solving this problem and promoting this transformation under atmospheric CO2
Material and Method: Arylboronic esters were synthesized according to the published procedure. Arylorganic
esters, silver compound, base, PPh3 and solvent were introduced into a 25 mL Schlenk flask. Then, the gasexchanging
operation via a “freeze-pump-thaw” method was conducted. After being enclosed with a CO2 balloon,
the resulting mixture was stirred at 70oC for 12 h. Then, the reaction was quenched by 1 M HCl and extracted
with ethyl acetate. The yields of the corresponding carboxylic acids were determined by GC. The structures
of products were confirmed by NMR and GC-MS.
Results: The carboxylation of arylboronic esters with ambient CO2 was achieved on the basis of the silver
chloride/triphenylphosphine system by using cesium carbonate as the base and dimethyl sulfoxide as the solvent.
Through this protocol, various functionalized carboxylic acids were synthesized in 85-99% yields.
Conclusion: The silver-catalyzed carboxylation of arylboronic esters with ambient CO2 was established. This
approach represents an alternative way to prepare carboxylic acids derivatives from the organoboron compounds
with CO2 under mild reaction conditions.