In the presence of catalytic amounts of optically active aminoalcohols, the irradiation of α- disubstituted indanones, tetralones and propiophenones bearing at least one hydrogen in the γ-position led to Norrish type II cleavage compounds which were obtained with enantiomeric excesses reaching 89%. The influence of the reaction conditions (temperature, wavelength of the UV light and nature of the alcohol) has been analyzed.