Synthesis and structure of dihydro‐1,2,4‐triazin‐6(1H) ones

Abstract

Reactions of the iminoesters 3a‐c with hydrazine or 1,2‐dimethylhydrazine gave 4,5‐dihydro‐4a‐c or 2,5‐dihydro‐1,2,4‐triazin‐6(1H) ones 7a‐c, respectively. When methylhydrazine was employed, 1‐methyl‐4, 5‐dihydro‐ 5a‐c and 2‐methyl‐2,5‐dihydro‐1,2,4‐triazin‐6(1H) ones 6a‐c were obtained. Compounds 6a‐c exist as zwitterions in the solid state and in polar aprotic solvents.

Trifluoromethylated 4,5-Dihydro-1,2,4-triazin-6(1H)-ones via (3+3)-Annulation of Nitrile Imines with α-Amino Esters

“…Thus, the presented method offers straightforward access to the desired heterocyclic system functionalized not only with simple alkyl and aryl substituents, but also with such functional groups as nitro, cyano, hydroxy, amino, methoxycarbonyl, and sulfide, as well as 1 H -indol-3-yl and halogen(s). Taking into account the easy accessibility of the starting materials and the exceptionally mild reaction conditions, the presented approach can be recommended for the synthesis of title 3-trifluoromethylated heterocycles, and nicely supplements previous reports on the synthesis of 1,2,4-triazin-6(1 H )-ones exploiting amino acids and their derivatives as key building blocks [ 56 , 57 , 59 , 60 , 61 , 62 , 63 , 64 ].…”

3,5-Diphenyl-1,2,4-triazin-6(1H)-one: synthesis, and X-ray and DFT-calculated structures

“…Yellow needles of (I) were filtered off and dried in air [yield 0.35 g, 14%; m.p. 494-495 K, reference 491-493 K (Camparini et al, 1978)]. Due to the fact that the oxidation of 3,5-diphenyl-4,5-dihydro-1,2,4-triazin-6(1H)-one occurred simultaneously with the crystallization of (I), the crystals of (I) obtained were of poor quality (cracked) and weakly diffracting.…”

Six‐Membered Heterocycles: Triazines, Tetrazines and Other Polyaza Systems

“…The reaction of imidate ester 163 with substituted hydrazines is a known reaction for the preparation of 1-substituted 4,5-dihydro-1,2,4-triazin-6(1H)-one 164 [177,261,262]. This synthesis has also been studied in the solid phase [263] (Scheme 20.48).…”

“…UV spectra have been used to determine tautomeric structures in 1,2,4-triazin-3-ones [172][173][174], 1,2,4-triazin-5-ones [175,176], 1,2,4-triazin-6-ones [177], 1,2,4-triazinethiones [178] and amino-1,2,4 triazines [179]. Unsubstituted 1,2,4-triazine [180] 2 has two absorption bands in methanol, at 374 (e ¼ 400) and 247.8 nm (e ¼ 3020).…”

“…Similarly, hydrazine or substituted hydrazines react with N-alkyl(N-acyl) a-aminoester [255], malonamide [256], a-imidoyl esters [177], a-isocyano esters [257], and (2)] fragment is the reaction of diazonium salts or other diazo compounds with activated methylene groups to obtain 1,2,4-triazin-3,5-dione [260].…”