Birch reduction of enones

Birch reduction of enones provides for a number of useful synthetic applications ... 

Addition of an alkyl group at C17 initially involves conditions fairly similar to those used in the Birch reduction of enones. A solution of the steroid in liquid ammonia and some inert co-solvent is first treated with lithium metal (Scheme 6.20). The resulting anion 20-1 is then quenched with an alkyl halide instead of the alcohol usually employed in Birch reductions. The anion at C17 then displaces the halogen, in the case at hand iodide, from the alkyl group to form a carbon-carbon bond and the 17a-methyl derivative 20-2. 

Stork and coworkers [127] were the first to demonstrate that hthium enolates are formed in the course of a Birch reduction of enones with lithium in ammonia, that they are regio-stable and can be trapped by electrophiles, as shown by the formation of traws-tetralone 111 through enolate 110 (Scheme 2.33). 

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