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Aliphatic and aromatic amines are converted by successive treatment with (i) 3-methyl-2-methylthiobenzothiazolium iodide, (ii) methyl iodide or toluene-p-sulphonate, and (iii) butylamine, in high yield under mild conditions into their mono-N-methyl derivatives.
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Katritzky et al. (1987) studied this question.
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