New transformations of 2-methylsulfanyl-4,6-dichloropyrimidine- 5-carbaldehyde involving enamines: synthesis of condensed azines

The reaction between 4,6-dichloropyrimidine-5-carbaldehyde and methyl 3-aminocrotonate leads to pyrido[2,3-d]pyrimidine which reacts with ethyl 3,3-diaminoacrylate to give pyrimido[4,5,6-de][1,6]naphthyridine derivative. The structure of the latter was confirmed by XRD analysis.