Selectivite de la reduction d'α-enones polycycliques par les borohydrures: effet de l'addition de tetramethyl-ethylenediamine au borohydrure de tetrabutylammonium

3^1,9octalone, 3^1,9-10-methyl octalone and testosterone were reduced by NBu₄BH₄. alone or in the presence of tetramethylethylenediamine (TMEDA), in THF and in toluene. With TMEDA, the first step of the reduction is the regioselective 1,4 attack by BH^?₄ which leads either to the saturated ketones or to the corresponding saturated alcohols. The results observed under different conditions were interpreted by the intervention of various reductive species: diborane, enoxyborohydrides in the absence of TMEDA, amine-borane in its presence.