method for the preparation of 2,4-disubstituted pyrido[2,3-d]pyrimidines is reported from 2,4-dimethylsulfanyl-pyrido[2,3-d]pyrimidines through a Liebeskind-Sroglcoupling reaction involving an original selective methyl sulfanyl discrimination using UV light as a source of energy. Our strategies involve a two-step and a one-pot approach with reaction times of 11-18 h and yields ranging between 72 and 94%