Chalcones are very desirable starting materials in medicinal chemistry since they can be produced artificially or naturally and are known to display a variety of biological functions. Chalcones have been found to possess a reactive α,β-unsaturated keto functional group, which is the source of their biological action. It is well known that pyrido[2,3-d]pyrimidines are pharmacophoric components in a wide range of active compounds with diverse pharmacological activities. By using the Claisen-Schmidt condensation method, several aromatic aldehydes (2a-k) were combined with 4-aminoacetophenone (1) to create chalcones 3a-k. When guanidine hydrochloride was used to cyclize these 4-aminochalocones under basic alcoholic conditions, 2,4,6-trisubstituted pyrimidines 4a–k were produced with quantifiable quantities. A straightforward regioselective cyclization was used to create the novel 4-amino-5,7-disubstituted pyrido[2,3-d]pyrimidines 6a-g. This was accomplished by aromatizing 2-amino-3-cyano-4,6-disubstituted pyridines 5a-k, which were derived from 4-aminochalcones 3a-k. All the synthesized compounds were characterized by spectroscopic means (FT-IR, 1H & 13C NMR) and elemental analysis and screened for antimicrobial activity. All the molecules were found to possess better activity against microbes.