One‐pot effective synthesis of new heterocyclic system: Pyrano[4′,3′:4,5]pyrido[2,3‐d]pyrimidin‐6‐one

One‐pot effective methods for the synthesis of derivatives of 6‐amino‐3,3‐dimethyl‐7‐aryl substituted‐8‐thioxo(oxo)‐pyrano[3,4‐c]pyridineswere developed. The proposed mechanisms of one‐pot reactions are presented. The derivatives of 8‐oxo‐pyrano[3,4‐c]pyridines served as starting materials for the synthesis of a new heterosystem—pyrano[4′,3′:4,5]pyrido[2,3‐d]pyrimidin‐6‐one. The antimicrobial activity of the obtained compounds was studied.