Methyleneammonium ions

The reactions of enamines with electrophiles follow a similar course and are also of OE t type. Enamines are isoconjugate with enolate ions and can likewise react with electrophiles in two different ways, either on nitrogen to form an enammonium ion or on carbon to form a methyleneammonium ion. As in the case of enolate ions, protonation takes place more rapidly on the heteroatom (here nitrogen) rather than carbon while allyl halides, e.g., methyl iodide, give C-alkylated products e.g.. 

Methyleneammonium ions [e.g. (137)] are more stable than the isomeric enammonium ions [e.g., (136)], just as simple ketones are more stable than the corresponding enols, because the sum of the C=N and C—C bond energies in, e.g., (137) is greater than that of the C—N and C=C bond energies in, e.g., (136). The heat of reaction for attack on carbon will be correspondingly more negative than that for attack on nitrogen by an amount dE which will be independent of the electrophile ... 

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See also in sourсe #XX -- [ ]

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