Cobalt(II)-catalyzed reaction between polycyclic aromatic aldehydes and acetic anhydride. Formation of acylals, not 1,2-diketones

Abstract

Several polycyclic aromatic aldehydes were found to react with acetic anhydride in acetonitrile in the presence of excess CoCl 2 to afford the corresponding acylals [ArCH(OAc) 2 ]. The results are not consistent with the literature report (Ahmad, S.; Iqbal, J. J. Chem. Soc., Chem. Commun. 1987, 692) that substituted benzaldehydes afford 1,2-diketones under similar conditions. The cobalt(II)chloride probably promotes acylal formation through its weakly Lewis acid character