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

Abstract

A catalytic system containing PdCl 2(cod) (cod=1,5-cyclooctadiene) and a water-soluble phosphine PNS (PNS=Ph 2PCH 2CH 2C(O)NHC(CH 3) 2CH 2SO 3Li) in water/toluene solution exhibits activity in the carbonylation of benzyl bromide to benzeneacetic acid (87% yield) at 130°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 6H 5CH 2C(O)OCH 3 at 50–100°C under 5–10 atm of CO, TOF ca. 300 was achieved. The contribution of palladium(0) phosphine complexes was proved using the 31P{ 1H} 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 6H 5CH 2Br yielding an oxidative addition product, PdBr(C 6H 5CH 2)(PNS) 2, identified using the 31P{ 1H} NMR method. In CD 3OD solution containing Pd(PNS) 4 and C 6H 5CH 2Br saturated with CO, the ester described by the formula C 6H 5CH 2C(O)OCD 3 was identified. This suggests that the reaction of CO-insertion into PdC bonding is relatively fast.