Cobalt-Catalyzed Carbonylation of Benzyl Halides Using Polyethylene Glycols as Phase-Transfer Catalysts

Hydroxycarbonylation of benzyl and substituted benzyl chloride and bromide derivatives was achieved in good yields (up to 97.6%) and quantitative chemoselectivity, in the presence of Co2(CO)8 as the transition metal and polyethylene glycols as the phase-transfer catalyst in an organic solvent/20% aqueous NaOH two-phase system under mild conditions (1 bar CO, room temperature). η1-Benzyl-, η3-benzyl-, and (η1-phenylacetyl)cobalt carbonyls were investigated as intermediates of this catalytic process.