Nitrosamines deprotonation

Dipole-Stabilization is a term coined by Beak to describe the situation that results when a carbanion is stabilized by an adjacent dipole. Such a situation arises when, for example, an amide is deprotonated a to nitrogen. The chemistry of these systems has been reviewed, - so only a few pertinent points will be made here. Firstly, metalation occurs syn to the carbonyl oxygen, and when the system is cyclic, the equatorial proton is removed selectively, and the electrophile attacks equatorially, as shown in equation (5), 24, 25 Thus, in contrast to nitrosamines, amide anions give the less stable equatorial product. 4,i25... 

The amine functions as a nucleophile and attacks a nitrosonium ion that was generated in situ from sodium nitrite and HCl. The resulting ammonium ion is then deprotonated to give the product. Nitrosamines are known to be potent carcinogens. Several examples are shown below ... 

The course of the reaction now depends on whether the amine nitrogen bears zero, one, or two hydrogens. Tertiary A-nitrosammonium salts are stable only at low temperatures and decompose upon heating to give a mixture of compounds. Secondary A-nitrosammonium salts are simply deprotonated to furnish the relatively stable A-nitrosamines as the major products. 

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