A new synthesis of 6-substituted pyrido[2,3-d]pyrimidines

The reaction of the β-methylsulfanylacroleins, derived from alkenyl sulfides by the Vilsmeier reaction, with 6-aminouracils or 2,6-diaminouracil, provides a new synthetic route to the 6-substituted pyrido[2,3-d]pyrimidines by two methods, the reaction mechanisms of which were examined by a deuterium-labeled thioacrolein.