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: R and R which may be identical or different denote a radical chosen from: a) a hydrogen atom； b) a C C alkyl group optionally interrupted with N S or O optionally substituted with one or more group(s) chosen from OR SR NRR CONHR3； COOR； and an aryl group optionally substituted with one or more hydroxyls and/or with one or more C C alkoxy radicals；c) a C C alkyl group substituted with a C C aryl radical optionally substituted with one or more hydroxyls and/or with one or more C C 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 C C alkyl group R denoting H a C C hydrocarbon based group or an acetyl group； it being possible for R and R 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.
