The carbonylation of phenyl bromide and its derivatives under visible light irradiation

The carbonylation of phenyl bromide catalyzed by Co(OAc)2 has been investigated with PhCOPh as a sensitizer under visible light in the presence of basic additive. With strong base CH3ONa, PhCOOCH3 is produced in 70 % yield with 100 % selectivity, the similar results are also obtained with a stronger base (CH3)3CONa. However, with another strong base NaOH, the yield of the ester is only 40 %. On the other hand, with weak base NaOAc or (n-C4H9)3N, phenyl bromide cannot be carbonylated. The results of carbonylation of the six substituted phenyl bromides suggest that the activities of o, m, p-BrC6H4CH3 are similar to phenyl bromide, while the activities of o, m, p-BrC6H4Cl are higher with the high yields (≥ 93 %) of the corresponding chloro-esters. In addition, the relative position of bromine and chlorine or methyl on phenyl ring has little effect on the activity of the carbonylation.