Formylation of 4,7-dihydro-1,2,4-triazolo[1,5-a ]pyrimidines using vilsmeier-haack conditions

Article abstract of DOI:10.1002/jhet.875

Formylation of 5-methyl-7-phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a] pyrimidine 1a using Vilsmeier-Haack conditions yields 5-methyl-7-phenyl-4,7- dihydro-1,2,4-triazolo[1,5-a]pyrimidin-6-ylcarbaldehyde 3a. 5,7-Diaryl-4,7- dihydro-1,2,4-triazolo[1,5-a]pyrimidines 1b,c in this reaction apart from formylation undergo recyclization into 5-aryl-1,2,4-triazolo[1,5-a]pyrimidin-6- ylmethane derivatives 4b,c, 5b,c, and 6. The structure of the synthesized compounds was determined on the basis of NMR, IR, and MS spectroscopic data and confirmed by the X-ray analysis of the 6-(ethoxy-phenyl-methyl)-5-phenyl-[1,2,4] triazolo[1,5-a]pyrimidine 6, 5-phenyl-6-(1-phenyl-vinyl)-[1,2,4]triazolo[1,5-a] pyrimidine 11, and 7-phenyl-6-(1-phenyl-vinyl)-[1,2,4]triazolo[4,3-a]pyrimidine 12.