Octalone metal-ammonia reduction

A classic method for generating regio-defmed enolates is metal-ammonia reduction of an enone. Stork and d Angelo found that the enolate resulting from lithium-ammonia-r-butyl alcohol reduction of octalone (3), followed by evaporation of ammonia, suspension of the enolate in ether and treatment with... 

Metal in ammonia reduction of bicyclic enones, especially terpenoid or steroid systems, has been intensively investigated and occurs with a high degree of diastereoselectivity. Stork has formulated the general rule that the reduction product is the more stable of the two isomers with the newly induced /1-hydrogen axial to the keto ring41,42. This rule is rationalized in terms of stereoelectronic effects in the transition state. For example, in reductions of octalones of type 1 only two (2 and 3) of three possible anionic transition states are stereochemically allowed. 

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