Sodium borohydride and lithium aluminium hydride are commonly used for the reduction of organic compounds. These two reagents are on the extremes of reactivity—whereas lithium aluminium hydride reacts with nearly all reducible functional groups, sodium borohydride reacts with a much more limited range of functional groups. Diminished or enhanced reactivity may be realized by the replacement of one or more of the hydrogens in these reagents with alkoxy groups.
Additionally, substitution of hydrogen for chiral alkoxy groups in these reagents enables asymmetric reductions. Although methods involving stoichiometric amounts of chiral metal hydrides have been supplanted in modern times by enantioselective catalytic reductions, they are of historical interest as early examples of stereoselective reactions.
The table below summarizes the reductions that may be carried out with a variety of metal aluminium hydrides and borohydrides. The symbol "+" indicates that reduction does occur, "-" indicates that reduction does not occur, "±" indicates that reduction depends on the structure of the substrate, and "0" indicates a lack of literature information.