Nontherapeutic cosmetic process for depigmenting, lightening and/or whitening keratin materials, which comprises the application of a cosmetic composition comprising, in a physiologically acceptable medium, at least one compound of formula: or its tautomer form of formula (I'): in which: R 1 denotes a radical chosen from: a) a hydrogen atom; b) a saturated linear C 1 -C 10 or branched C 3 -C 10 or unsaturated C 2 -C 10 alkyl group, optionally substituted with one or more OR 3 groups; R 2 denotes a radical chosen from: a) a saturated linear C 1 -C 10 or branched C 3 -C 10 or cyclic C 3 -C 7 alkyl group, optionally interrupted with one or more oxygen atoms, and/or optionally containing one or more groups, which may be identical or different, chosen from: i) -OR 3, ii) -NR 3 R 4, iii) -CONHR 3, iv) -COOR 3; b) a phenyl group optionally substituted with one or more hydroxyls and/or with one or more C 1 -C 3 alkoxy radicals; c) a saturated C 1 -C 5 alkyl group substituted with a phenyl radical optionally substituted with one or more hydroxyls and/or with one or more C 1 -C 3 alkoxy radicals; R 3 denoting a hydrogen atom or a saturated linear C 1 -C 5 or branched C 3 -C 5 hydrocarbon group; R4 denoting a hydrogen atom or a saturated linear C 1 -C 5 or branched C 3 -C 5 hydrocarbon group. and also the salts thereof, the optical isomers thereof and the racemates thereof. R 1 denotes a radical chosen from: a) a hydrogen atom; b) a saturated linear C 1 -C 10 or branched C 3 -C 10 or unsaturated C 2 -C 10 alkyl group, optionally substituted with one or more OR 3 groups; a) a hydrogen atom; b) a saturated linear C 1 -C 10 or branched C 3 -C 10 or unsaturated C 2 -C 10 alkyl group, optionally substituted with one or more OR 3 groups; R 2 denotes a radical chosen from: a) a saturated linear C 1 -C 10 or branched C 3 -C 10 or cyclic C 3 -C 7 alkyl group, optionally interrupted with one or more oxygen atoms, and/or optionally containing one or more groups, which may be identical or different, chosen from: i) -OR 3, ii) -NR 3 R 4, iii) -CONHR 3, iv) -COOR 3; b) a phenyl group optionally substituted with one or more hydroxyls and/or with one or more C 1 -C 3 alkoxy radicals; c) a saturated C 1 -C 5 alkyl group substituted with a phenyl radical optionally substituted with one or more hydroxyls and/or with one or more C 1 -C 3 alkoxy radicals; a) a saturated linear C 1 -C 10 or branched C 3 -C 10 or cyclic C 3 -C 7 alkyl group, optionally interrupted with one or more oxygen atoms, and/or optionally containing one or more groups, which may be identical or different, chosen from: i) -OR 3, ii) -NR 3 R 4, iii) -CONHR 3, iv) -COOR 3; i) -OR 3, ii) -NR 3 R 4, iii) -CONHR 3, iv) -COOR 3; b) a phenyl group optionally substituted with one or more hydroxyls and/or with one or more C 1 -C 3 alkoxy radicals; c) a saturated C 1 -C 5 alkyl group substituted with a phenyl radical optionally substituted with one or more hydroxyls and/or with one or more C 1 -C 3 alkoxy radicals; R 3 denoting a hydrogen atom or a saturated linear C 1 -C 5 or branched C 3 -C 5 hydrocarbon group; R4 denoting a hydrogen atom or a saturated linear C 1 -C 5 or branched C 3 -C 5 hydrocarbon group. and also the salts thereof, the optical isomers thereof and the racemates thereof.