The remarkable role of water during the chemoselective reduction of ketones mediated by metallic aluminium

Diaryl ketones are reduced selectively to the corresponding benzhydrols in good yield by aluminium powder in the presence of sodium hydroxide in the solvent system MeOH:H2O=2:1 whereas dialkyl ketones, α-tetralone, aryl alkyl ketones and cycloalkanones remain mostly unaffected. Interestingly, diaryl ketones remain totally unchanged by the present reagent combination in the absence of water, that is in anhydrous methanol.