Carbodeoxygenation of biomass: the carbonylation of glycerol and higher polyols to monocarboxylic acids.

Glycerol is converted to a mixture of butyric and isobutyric acid by rhodium- or iridium-catalysed carbonylation using HI as the co-catalyst. The initial reaction of glycerol with HI results in several intermediates that lead to isopropyl iodide, which upon carbonylation forms butyric and isobutyric acid. At low HI concentration, the intermediate allyl iodide undergoes carbonylation to give vinyl acetic acid and crotonic acid. Higher polyols C(n)H(n+2)(OH)(n) are carbonylated to the corresponding C(n+1) mono-carboxylic acids.