[en] The use of LiGaH₄ in combination with the S,O-chelate 2-hydroxy-2'-mercapto-1,1'-binaphthyl (monothiobinaphthol, MTBH₂), forms an active catalyst (2 mol %) for the asymmetric reduction of prochiral ketones, when using catecholborane as the hydride source. This catalyst has successfully been applied to the enantioselective reduction of aryl/n-alkyl ketones, providing the chiral sec-alcohols in yields of 82 - 96% and with enantiomeric excess values of 59 - 93%. Alkyl/methyl ketones are reduced in yields of 72 - 93% and in 46 - 79% enantiomeric excess. Enantioface differentiation is on the basis of the steric requirements of the ketone substituents. The X-ray structure of the pre-catalyst, Li(THF)₃Ga(MTB)₂ has been determined and in solution is in equilibrium with a dimeric species of constitution Li₂Ga₂(MTB)₄. An indium analogue whose X-ray structure was determined as Li₂(THF)₅lnCI(MTB)₂ has also been prepared. The indium- based catalyst does not form an enantioselective catalyst. The enantioselectivity of the catalytic reaction is highly dependent on the nature of the borane species used. Various boranes were compared in their efficiency to enantioselectively reduce acetophenone and only catecholborane produced the corresponding sec-alcohol in high yield and enantiomeric purity. In the presence of mixtures of tetraallyltin and triallylalkyltins, MTBH₂ (20 mol %) acts as a chiral promoter for the highly enantioselective allylation of aryl/methyl ketones providing chiral tert-homoallylic alcohols with enantiomeric excesses of up to 88% and yields >98%. The individual use either of the allyltin species proved ineffective. The enantioselectivity of the catalytic reaction is initially very high with enantioselectivities >90%, but was shown to decrease with increasing reaction conversion. However, the presence of small amounts of water results in a catalytic reaction where the enantioselectivity is independent of the reaction conversion, thus, allowing ketones to be allylated in high yield and with high enantiomeric excesses. (author)