Simplified carbonylation catalyst based on [Co2(CO)8] and coordinating solvents for the carbonylation of β-lactones and α,β-unsaturated acids to cyclic anhydrides

Cyclic anhydrides are valuable chemical intermediates and monomers that can be synthesized through the carbonylation of oxygenated substrates like β-lactones and unsaturated acids. Sophisticated cobalt-based catalysts, which require the addition of ligands or presynthesis of a metal cation, have been extensively used to promote such reactions. Herein, we show that the commercial complex [Co2(CO)8] is a suitable catalytic precursor for the carbonylative ring expansion of β-lactones in a wide range of conditions and even at low CO pressure. In particular, succinic anhydride is formed quantitatively from β-propiolactone in the presence of only [Co2(CO)8] in acetonitrile under a moderate CO pressure. The carbonylation of acrylic acid in these conditions is also possible, and provides quantitative yields of product when the gas phase includes H2. This work reinvestigates the potential of [Co2(CO)8] as a catalyst precursor: its disproportionation in the presence of a coordinating solvent (including MeCN and acetone) yields active catalytic species and thus paves the way toward the design of simpler catalytic systems for carbonylation reactions.