Oxidation of ω-(Benzoyloxy)alkanols with an Oxoaminium Salt

Article abstract of DOI:10.1021/jo00292a021

Oxoaminium chloride (2), the oxidized derivative of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, 1), was found to display a novel selectivity in the oxidation of ester group containing alcohols.The oxidation of (2 to 6)-(benzoyloxy)alkanols and related alcohols were carried out at room temperature with 1.0 equiv. of the oxoaminium chloride in dichloromethane (method A) or with 0.1 equiv. of TEMPO, 1.5 equiv. of cupric chloride, and 1.5 equiv. of cupric hydroxide (method B).Whereas the oxoaminium chloride did not significantly oxidize 2-(benzoyloxy)ethanol and 3-(benzoyloxy)propanol, it did oxidize 4-(benzoyloxy)butanol, 5-(benzoyloxy)pentanol and 6-(benzoxyloxy)hexanol to the corresponding (benzoyloxy)alkanals.The origin of this selectivity was investigated, and NMR and other studies suggest that the selectivity might be attributed to the inductive effect of the ester group.