Baxitozine

A reaction of 6‐amino‐1,3‐dimethyluracil with 3‐(hetero)aroylacrylic acids and their methyl esters leads to hexahydropyrido[2,3‐d]pyrimidine‐5‐carboxylic acids or the corresponding methyl esters in high to excellent yields. One‐pot oxidation of the acid derivatives with CAN is accompanied by decarboxylation to give tetrahydropyrido[2,3‐d]pyrimidines, while oxidation with bromine resulted in the formation of tetrahydropyrido[2,3‐d]pyrimidine‐5‐carboxylic acids. The aromatization of methyl hexahydropyrido[2,3‐d]pyrimidine‐5‐carboxylates was achieved by K2CO3‐mediated air oxidation under ambient conditions.