A sustainable route for the synthesis of alkyl arylacetates via halogen and base free carbonylation of benzyl acetates†
The unprecedented palladium catalysed carbonylation of benzyl acetate derivatives herein presented allowed a broad library of alkyl arylacetates in excellent yields to be obtained. Notably, no use of halogen or base additives was required to perform the reaction. Furthermore, all reactions were accomplished at carbon monoxide ambient pressure, increasing the sustainable feature of the protocol reported. The binary system palladium acetate (2 mol%)/DPPF (4 mol%) (DPPF = 1,1′-bis(diphenylphosphino)ferrocene) was found to be the best performing catalyst at 130 °C and 18 hours for different carbonylative transformations, such as alkoxycarbonylation in the presence of several alcohols and hydroxycarbonylation of benzyl acetates. The synthesis of the substrates was achieved by simply treating benzyl alcohol with cheap, safe and non-toxic isopropenyl acetate (IPAc). IPAc is an emerging acetylating agent which allows acetates under mild reaction conditions to be obtained, producing only acetone as the by-product. Thus, the whole process is completely halogen free. Finally, a set of control experiments and DFT studies led to the identification of a plausible reaction pathway.