One-Pot Synthesis of 5,7,8,9,9a,10-Hexahydro-8-thioxotetrahydropyrido[2,3-d : 6,5-d′]dipyrimidine-2,4,6(1H,3H,5aH)-triones via a Four-Component Coupling Reaction of Aldehydes, Amines, Barbituric Acids, and Thiouracil

An efficient one‐pot approach to the synthesis of 5,7,8,9,9a,10‐hexahydro‐8‐thioxopyrido[2,3‐d : 6,5‐d′]dipyrimidine‐2,4,6(1H,3H,5aH)‐triones 5 via a four‐component reaction of an aldehyde 1, an amine 2, a barbituric acid 3, and thiouracil (4) is reported for the first time. This new multicomponent reaction is accomplished in refluxing EtOH in the presence of tungstophosphoric acid (H3PW12O40) as a catalyst. A variety of hexahydropyrido[2,3‐d : 6,5‐d′]dipyrimidinetrione derivatives were successfully synthesized in excellent yields with this protocol (Table 2).