Synthesis of New Substituted 1,2,4‐Triazines from Isonitrosoketones and Terephthalaldehydedihydrazone

Abstract

This study describes a novel method for the synthesis of 1,2,4‐triazines. Firstly, isonitrosoacetophenone, p‐methylisonitrosoacetophenone, and isonitroso‐1‐acetylnaphthalene were synthesized from the reaction of butylnitrite with acetophenone, p‐methylisonitrosoacetophenone, and 1‐acetylnaphthalene, respectively. Then, symmetric derivatives of 1,2,4‐triazines were prepared from the condensation reaction of keto oximes with terephthalohydrazone. However, the heteroaromatic closure was not observed in the condensation reaction of pyruvic‐aldehyde‐1‐oxime(keto oxime) with terephthalohydrazone. Structures of the obtained products were confirmed by FTIR, 1H‐NMR, and elemental analyses techniques.

Pot, Atom, Step Economic (PASE) Approach towards (Aza)‐2,2′‐Bipyridines: Synthesis and Photophysical Studies

“…However, the serious drawback of this approach is the formation of isomeric 3,5‐disubstituted 1,2,4‐triazines as side‐products. Some other approaches were also reported, such as the thermolysis of α‐azido ketone acylhydrazones, the interaction of iso‐ nitrosoacetophenones either with amidrazones in acidic conditions (in some cases the 1,2,4‐triazine‐4‐oxides are also formed), or with hydrazones of aldehydes . Few recent methods should be also mentioned, for example, the rhodium‐catalyzed cyclocondensation of aza vinylcarbenes with N ‐acylhydrazones, a synthesis based on 2‐chloro‐ N ‐(2‐(4‐chloro‐phenyl)‐2‐oxoethyl)‐propan‐amide, hydrohydrazination of propargylamides with BocNHNH 2 in presence of Zn(OTf) 2 and, finally, acid‐catalyzed ring‐opening / cyclization / oxidation of aziridines with N ‐tosylhydrazones …”

“…Some other approaches were also reported, such as the thermolysis of a-azido ketone acylhydrazones, [14] the interaction of iso-nitrosoacetophenones either with amidrazones in acidic conditions (in some cases the 1,2,4triazine-4-oxides are also formed [15] ), or with hydrazones of aldehydes. [16] Few recent methods should be also mentioned, for example, the rhodium-catalyzed cyclocondensation of azavinylcarbenes with N-acylhydrazones, [17] a synthesis based on 2-chloro-N-(2-(4-chloro-phenyl)-2-oxoethyl)-propan-amide, [18] hydrohydrazination of propargylamides with BocNHNH 2 in presence of Zn(OTf) 2 [19a] and, finally, acid-catalyzed ring-opening / cyclization / oxidation of aziridines with N-tosylhydrazones. [19b] Based on a critical analysis of the literature, the heterocyclization of in situ generated iminoesters 1 with readily available isonitrosoacetophenone hydrazone 2 [20] have been selected as the most convenient synthetic approach towards 3,6-disubstituted 1,2,4-triazines (Scheme 2).…”

Regioselective Synthesis of V-Shaped Bistriazinyl-phenanthrolines

“…21 The second strategy (route B) starts with conversion of 1,10-phenanthroline-2,9-dicarbaldehyde into 2,9-bis((E)-hydrazonomethyl)-1,10-phenanthroline and subsequent condensation of the obtained bishydrazone with (Z)-2-(4-bromophenyl)-2-oxoacetaldehyde oxime into the desired 4BrPhBTPhen ligand. 22 The third strategy (route C) is a modification of route B: instead of reacting 1,10-phenanthroline-2,9-dicarbaldehyde with hydrazine, (Z)-2-(4-bromophenyl)-2-oxoacetaldehyde oxime is allowed to react with hydrazine to form (1E,2Z)-2-(4-bromophenyl)-2-hydrazonoacetaldehyde oxime; subsequent condensation with 1,10-phenanthroline-2,9-dicarbaldehyde yields the desired 4BrPhBTPhen ligand product. [23][24][25] …”

“…Condensation of compounds 4 and 5 in ethanol, as described in the literature22 was not possible since compound 4 is insoluble in ethanol and other solvents, such as THF, 1,4-dioxane and acetic acid. Attempts to drive the reaction at higher temperature under reflux did not work.…”

Triazines: Syntheses and Inverse Electron-demand Diels–Alder Reactions

“…In 2010, Karatas and Alici described a [3 + 3] annulation reaction of keto oximes with hydrazones to construct a special type of symmetric 1,2,4-triazines 23 (Scheme ). While three aromatic keto oximes were smoothly transformed into the corresponding a -triazines 23a – 23c , methyl-substituted substrate only gave the condensation product 24 without ring closure. In 2017, Crespin et al disclosed a one-pot acid-catalyzed [3 + 3] annulation process for the regioselective conversion of N -tosyl hydrazones and aziridines into 3,6-disubstituted and 3,5,6-trisubstituted 1,2,4-triazines (Scheme ).…”