Scope and mechanism of the phase-transfer carbonylation of organic halides catalyzed by pentacarbonyliron to give ketones and carboxylic acids

Various substituted benzyl halides are readily converted into 1,3-diaryl-2-propanones, RCOR, or arylacetic acids, RCO 2 H (R=ArCH 2 ), under CO pressure on reaction with a catalytic amount of pentacarbonyliron in a liquid-liquid phase transfer system(CH 2 Cl 2 (or C 6 H 5 CH 3 )/H 2 O, NaOH, (Bu 4 N + ) 2 SO 4 2− ). These reactions involve the in situ generation of the acyltetracarbonyliron anion, RCOFe(CO) 4 − , which is maintained in the organic phase as the tetrabutylammonium ion pair. Further reaction of benzyl halides with this anion starts the catalytic conversion to give either ketones, RCOR, or acids, RCO 2 H