Considering its performances, DMF is not suitable for this reaction (less of 5% of yield, and very low selectivity, Table , entries 28-30). In MeCN and THF, the optimal reactivity is obtained under moderate pressure (15 bar, Table , entries 7-9, 25-27). a Conditions: PL (0.5 mol‧L -1 ) and mesitylene (internal standard, 10 mol%) with [Co2(CO)8] (5 mol%) in the solvent (2 mL), heated for 6 h under CO pressure. PL conversions and SA yields were measured by GC-MS analysis; the selectivity was calculated as the ratio between yield and conversion. Due to the uncertainty of the analysis method, conversions lower than the yields can be obtained, and in that case, the selectivity value was reported as >99%. Selectivity was not reported and noted "/" when the conversion was <1%.