RuO4-mediated oxidation of N-benzylated tertiary amines. 2. Regioselectivity for N,N-dimethyl- and N,N-diethylbenzylamine as substrates

N,N-Dimethyl-(1A) and N,N-diethylbenzylamine (1B) underwent RuO 4 -mediated oxidation by attack at both types of (N-α)C-H bonds (i.e., alkyl and benzyl) to yield the corresponding Nalkyl-N-benzylamides [and N-methyl-(8A) or N-ethylbenzylamine (8B), resp.] and benzaldehyde (and N,N-dialkylbenzamides), respectively.Oxidation of 8A-B occurred also, as well as their reaction with formaldehyde or acetaldehyde, respectively, equally formed during the oxidation of 1A-B or 8A-B.Initial formation of the iminium cations from 1A-B was proved by their capture as nitriles.The statistically corrected alkyl/benzyl regioselectivity of the oxidation reaction was 4.1 for 1A and 2.1 for 1B.Comparison with the results obtained on Nbenzylpiperidine showed that RuO 4 does not discriminate axial and equatorial CH bonds in the piperidine ring.The N-α-C .carbon-centered radical and the amine cation radical seem not to be involved as precursors of the iminium cations.