A facile clean synthesis of pyrido [2,3- d ] pyrimidine and their derivatives in ionic liquids

Chalcone on reaction with malononitrile in ionic liquid affords 2-amino-3-cyano-4,6-disubstituted pyridines in excellent yield. The pyridine derivatives are used as precursor for the synthesis of 5,7-disubstituted pyrido[2,3-d] pyrimidine-4(3H)-one 4a-d and 5,7-disubstituted pyrido[2,3-d]pyrimidine-2,4 (1H,3H)-dithione 5a-d derivatives. The heterocyclic bases, namely 2,4-disubstituted-5-thioxo-7,8-dihydro-pyrido[2',3':4,5]pyrimido[2,1-b][1,3]thiazin-9-ones 6a-d, 2,4-disubstitued-5-thioxo-pyrido[2',3':4,5]pyrimido[2,1-b][1,3] thiazol-8-ones 7a-d, 8-(4-chlorobenzylidene)-2,4-disubstitued5-thioxo-7,8-dihydro-pyrido[2',3':4,5]pyrimido[2,1-b][1,3]thiazin-9-ones 8a,b and 7-(4-chlorobenzylidene)-2,4-disubstitued5-thioxo-pyrido[2',3':4,5]pyrimido[2,1-b] [1,3]thiazol-8-ones 9a,b derivatives have been thus synthesized. The structure of all the synthesized compounds have been established by elemental analysis, IR, 1 H and 13 C NMR spectral data.