Résumé
The direct, catalytic carbonylation of aryl iodides to give the corresponding benzophenones is reported for the first time. Under phase transfer conditions (aq. NaOH/C
6H
6/Bu
4NBr) and under 1 atm pressure of carbon monoxide, iron pentacarbonyl alone promotes the conversion of iodobenzene to benzophenone and benzoic acid, whereas dicobaltoctacarbonyl alone promotes a slow carbonylation to give solely benzoic acid. A synergetic effect is observed when the reaction is carried out in the presence of catalytic amounts of both carbonyl metals, and benzophenone can be isolated in more than 50% yield. Under these conditions,
o-iodotoluene affords the corresponding 2,2′-dimethylbenzophenone in 47% isolated yield.