A-methoxylation of tertiary amine

The Ru(II)/ROOH system can also be used to oxidize tertiary amines. The intermediate iminium ion is formed, as described earlier for secondary amines, and can be trapped by nucleophiles. Thus, the ruthenium-catalysed oxidation of tertiary amines with hydrogen peroxide in methanol can be performed to give the corresponding a-methoxyamines with high efficiency as illustrated in Fig. 24 [ 137]. Another example is the selective demethylation of tertiary amines in methanol with a combination of Ru(II) and H202, followed by hydrolysis of the intermediate a-methoxylated amines. For example, the methoxylation of N,N-dimethyl-p-toluidine followed by treatment with 2 N HC1 solution gave N-methyl-p-toluidine in 75% yield (Eq. 35) [137]. 

CH bonds a to an amino group Anodic methoxylation of unsymmetrical tertiary amines takes place preferentially at the methyl group (Fig. 6) [28-30]. Substitution at a CH bond a to an amino group proceeds by oxidation of the amino group to a radical cation, followed by deprotonation at the adjacent CH bond to a radical. This is oxidized to a cation, which undergoes solvolysis, in this case, methanolysis. The regioselectivity has been explained by assuming that an adsorbed amine from which the intermediate cation is formed is as distant as possible from the anode... 

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