The problem of double compared with single alkylation of ketones by iodomethane and base is mentioned in Section 18-4. Write a detailed mechanism showing how some double alkylation occurs even when only one equivalent each of the iodide and base is used. Suggest a reason why the enamine alkylation procedure solves this problem.

Data From Problem Section 18-4

We have seen that enolates may be generated from ketones and aldehydes by treatment with bases, such as LDA. The nucleophilic a-carbon of the enolate may participate in SN2 alkylation reactions with suitable haloalkanes, forming a new carbon – carbon bond in the process. This section presents some features of enolate alkylation and compares it with a related process, alkylation of a species called an enamine.