Pyrido2,3-dpyrimidine-2,7-dithiol in heterocyclic synthesis: Synthesis and characterization of several new fused pyridopyrimidine heterocycles

摘要

Pyridine-2(l1)-thione 1 reacted with phenyl isothiocyanate to give pyrido2,3-Jpyrimidine derivative 3. Compound 3 reacted with halogen containing compounds 4a-d and methyl iodide in dimethylformamide/potassium hydroxide solution at room temperature to give 2,7-bisalkylthiopyrido2,3-dpyrimidine derivatives 5a-d and 9, respectively. Compounds 5a-d could be cyclized into thienopyrido2,3-Jpyrimidine derivatives 6a-d by boiling with ethanolic potassium hydroxide solution. Compound 6a reacted with acetic anhydride or formic acid and gave the corresponding pyrimido4",5":4',5'thieno3',2':5,6pyrido2,3-rfpyrimidine derivatives 8a,b. Compound 9 reacted with hydrazine hydrate to yield pyrazolo4',3':5,6pyrido2,3-dpyrimidine derivative 11 which could be reacted with nitrous acid and dimethylformamide-dimethylacetal (DMF-DMA) and gave the final isolable products corresponding to the pyrazolo4',3':5,6pyrido2,3-dtetrazolo-5,l-d)pyrimidine and pyriniidol",2":r,5'pyrazolo4',3':5,6pyrido2,3-"d1.2,4triazolo-4,3-d pyrimidine derivatives 13 and 17, respectively. Compound 11 also reacted with some fi-dicarbonyl compounds such as acetylacetone (18) and ethyl acetoacetate (20) to yield the corresponding pyrimidol",2":l',ypyrazolo4',3':5,6pyrido2,3-dpyrimidine derivatives 19 and 21, respectively. Finally, compound 11 reacted with chloroacetyl chloride (22) to give the corresponding imidazoll'",2'":l",5"pyrazolo4",3":.'i',6'pyrido3',2':S,6pyrimido2,l-rl,2,4triazine derivative 23.