Synthesis of pyridine and pyrimidine derivatives by reaction of pyrylium salts with ureas, thioureas, and isothioureas

摘要: 2,4,6-Triphenylpyrylium perchlorate is converted to 2,4,6-triphenylpyridine in reactions with urea and N-acetyl- N,N-dimethylureas, whereas it 1,2,4,6-tetraphenylpyridinium on reaction N,N′-diphenylurea. The of pyrylium perchlorates thiosemicarbazide semicarbazide leads 1-thiocarbamido- 1-carbamidopyridinium salts. latter reacts 2,4,6-triphenylpyrylium give 1-aminopyridinium salts, which were acylated acetic anhydride. Difficult-to-obtain 2-alkylthio-4,6-diarylpyrimidines synthesized 40–93% yields by the 2,4,6-triarylpyrylium salts S-alkylisothioureas.