The invention relates to a cosmetic process for depigmenting, lightening and/or whitening keratin materials, in particular the skin, which comprises the application of a cosmetic composition comprising a compound of formula (I):or its tautomer form of formula (I′):in which:R1 and R2, which may be identical or different, denote a radical chosen from:a) a hydrogen atom；b) a C1-C20 alkyl group optionally interrupted with N, S or O, optionally substituted with one or more group(s) chosen from —OR3, —SR3, —NR3R4, —CONHR3； -COOR3； and an aryl group optionally substituted with one or more hydroxyls and/or with one or more C1-C8 alkoxy radicals；c) a C1-C8 alkyl group substituted with a C5-C12 aryl radical optionally substituted with one or more hydroxyls and/or with one or more C1-C8 alkoxy radicals；d) a phenyl group optionally substituted with one or more hydroxyls and/or with one or more C1-C8 alkoxy radicals；R3 denoting H or a C1-C5 alkyl group,R4 denoting H, a C1-C5 hydrocarbon-based group or an acetyl group；it being possible for R1 and R2 to form, with the nitrogen atom which bears them, a ring chosen from pyrrolidine, pyrroline, piperidine, piperazine, morpholine, thiomorpholine and azepine.The invention also relates to the cosmetic use of a compound (I) or (I′) as a whitening, lightening and/or depigmenting agent for keratin materials.
