The stereochemistry of alkali metal/ammonia reductions of stilbenes: Application in the synthesis of ¹⁴C-labelled meso-hexoestrol

Abstract

Some α,α-disubstituted stilbenes were reduced with lithium, sodium or potassium in anhydrous liquid ammonia by two procedures: (A) the alkali metal was added to a solution of the stilbene in ammonia/tetrahydrofuran; and (B) a solution of the stilbene in tetrahydrofuran was added to a preformed blue solution of the alkali metal in ammonia. For the more sterically crowded stilbenes the ratio of bibenzyl diastereoisomers formed differed according to the alkali metal and the reduction procedure used. The results were exploited in a synthesis of 2-¹⁴C-labelled meso-hexoestrol.