Oxidative dealkylation of 4-substituted N,N-dialkylanilines with molecular oxygen in the presence of acetic anhydride promoted by cobalt(II) or copper(I) chloride

The reaction of 4-substituted N,N-dimethylanilines 1a–d with acetic anhydride 5 proceeded efficiently in the presence of a catalytic amount of cobalt(II) or copper(I) chloride under oxygen to give the corresponding N-methylacetanilides 2a–d along with N-methylformanilides 3a–d. The reaction of N-alkyl-N-methyl-p-toluidines 1f–h with cobalt chloride revealed that the order of reactivity of the N-substituents follows the sequence allyl > benzyl methyl > ethyl, while in the case of copper chloride the order was benzyl > allyl > methyl > ethyl. Aldehydes 18a–e and phenylglyoxylic acid derivatives 18f and 18g were obtained in fair to good yield from the reaction of N-substituted N-ethyl-p-toluidines 17a–g.