Kondensationen mit Hydrazin‐N,N′‐dicarbonsäurediamidin, 22. Mitt. Aromatisch und aromatisch‐aliphatisch substituierte β‐Diketone als Reaktionspartner

Abstract

Wahrend im Gegensatzzu aliphatischen p-Diketonen l-Phenyl-1,3-butandion (2) bei Raumtemperatur nicht mit Hydrazin-N,N'-dicarbonsaurediamidin (1) reagiert, tritt bei erhohter Reaktionstemperatur Umsetzung unter Bildung von 2-Amino-5-methyl-7-phenyl-s-triazolo[ 1 $a]pyrimidin (4) ein. 4 wird auch bei der Umsetzung von 2 mit 3,5-Diamino-s-triazoI (5) gebildet. Condensations with 1,2-HydrPzinedicarboxamidine, XXII: Reactions with p-Diketones Carrying Aromatic or Aromatic-Aliphatic SubstituentsIn contrast to aliphatic P-diketones, l-phenyl-1,3-butanedione (2) does not react with 1,2-hydrazinedicarboxamidine ( 1 ) at room temperature. A reaction does occur, however, at elevated temperatures. It leads to 2-amino-5-methyl-7-phenyl-s-triazolo[ 1,5-a]pyrimidine (4), which is also formed in the reaction of 2 with 3,5-diamino-s-triazole (5). 03654233/79/1? 12-1003 S 02.50/0 8 Verlag Chernie. GrnbH. Weinheirn 197Y

Efficient and regioselective one-step synthesis of 7-aryl-5-methyl- and 5-aryl-7-methyl-2-amino-[1,2,4]triazolo[1,5-a]pyrimidine derivatives

“…Actually, Kreutzberger and Risse reported in 1979 that this reaction condition provided a mixture of isomers 1a and 2a in 2% and 26% yield, respectively. 8 In contrast to what reported by Kreutzberger and Risse who mistakenly inverted the assignment of the structures, we were pleased to find that the reaction took place rapidly (4 h), highly efficiently, and, more interestingly, highly regioselectively. Indeed, 2amino- 5-methyl-7-phenyl-[1,2,4]triazolo[1,5-a]pyrimidine (1a) was obtained in 88% yield while its regioisomer 2-amino-7-methyl- 5-phenyl-[1,2,4]triazolo[1,5-a]pyrimidine (2a) was formed only in traces.…”