Carbonylation of benzyl bromide to benzeneacetic acid and its esters catalysed by water-soluble palladium complexes

A catalytic system containing PdCl(2)(cod) (cod = 1,5-cyclooctadiene) and a water-soluble phosphine PNS (PNS = Ph(2)PCH(2)CH(2)C(O)NHC(CH(3))(2)CH(2)SO(3)Li) in water/toluene solution exhibits activity in the carbonylation of benzyl bromide to benzeneacetic acid (87% yield) at 130 degrees C and 10 atm of CO. In a reaction carried out in water/alcohol solution, corresponding esters were obtained in yields dependent on the kind of alcohol used: 24% for BuOH, 62% for (i)PrOH, 78% for EtOH, and 85% for MeOH. In the synthesis of benzeneacetic acid methyl ester C(6)H(5)CH(2)C(O)OCH(3) at 50-100 degrees C under 5-10 atm of CO, TOF ca. 300 was achieved. The contribution of palladium(0) phosphine complexes was proved using the (31)P{(1)H} NMR and IR methods. The complex Pd(PNS)(4), obtained in the reaction of PdCl(2)(cod) with PNS and NaBH(4), reacts with C(6)H(5)CH(2)Br yielding an oxidative addition product, PdBr(C(6)H(5)CH(2))(PNS)(2), identified using the (31)P{(1)H} NMR method. In CD(3)OD solution containing Pd(PNS)(4) and C(6)H(5)CH(2)Br saturated with CO, the ester described by the formula C(6)H(5)CH(2)C(O)OCD(3) was identified. This suggests that the reaction of CO-insertion into Pd-C bonding is relatively fast. (C) 2000 Elsevier Science B.V. All rights reserved.