Synthesis of higher carboxylic acids via reaction of polyols with CO2 and H2

Synthesis of value-added chemicals from biomass-derived polyols and CO2 is of great importance. Herein we report a strategy to produce higher carboxylic acids by the reaction of polyol, CO2, and H2. The reaction can be efficiently accelerated by Rh catalyst in a binary solvent of ionic liquid (1-butyl-3-methylimidazolium iodide) and water, where cheap and nontoxic I2 was used as a promoter. The reaction can occur at above 100°C. At optimal conditions, the yield of the carboxylic acids was as high as 86.4%. The catalytic mechanism is proposed based on a series of control experiments. Interestingly, the polyol could be effectively transformed into olefin intermediate at metal-free and mild conditions, which was the key to the success of this strategy. The peculiar solvent effect was also favorable to the reaction. In addition, the catalytic system was adaptable to various polyol substrates.