Benzylic halides, reaction with enamines

Enamines are intermediate in reactivity more reactive than an enol, but less reactive than an enolate ion. Enamine reactions occur under milder conditions than enolate reactions, so they avoid many side reactions. Enamines displace halides from reactive alkyl halides, giving alkylated iminium salts. The iminium ions are unreactive toward further alkylation or acylation. The following example shows benzyl bromide reacting with the pyrrolidine enamine of cyclohexanone. 

This reaction, designed by Gilbert Stork, fosters monoalkylation. Enamines —[see Problem 17.5(a)(5)], of ketones are monoalkylated with reactive halides, such as benzyl and allyl, in good yield at the a C. The enamines are made from the ketone and preferably a 2° amine, RjNH. 

---