SYNTHESIS AND X-RAY CRYSTAL STRUCTURE ANALYSIS OF SUBSTITUTED 2,3-DIHYDRO-1,3,4-OXADIAZOLES VIA REACTION OF ACETONE- AND CYCLOALKANONE BENZOYLHYDRAZONES WITH PHENYLISOCYANATE

Oximic 1,2,4-triazole ligands 2a-e were prepared from the reaction of 3-acetyl–4,5-dihydro-1H-1,2,4-triazoles 1a-e with hydroxylamine hydrochloride at room temperature. At higher temperatures, the reaction afforded, however, the novel ring transformation product 4-amino-2-(4-chlorophenyl)-5-methyl-2H-1,2,3,6-oxatriazine 3. The reaction of the ligands 2a-e with nickel(II) and palladium(II) acetates in ethanol at room temperature yielded the respective square planar complexes 5a-e, 6a,e rather than the simple bis oximato metal(II) complexes that have been suggested before. X-ray structure determination of one of these complexes (5a) revealed that metallation led to unexpected ring transformation of the triazole ligand. It is probable that such ring transformation generated the imidazole-N-oxide intermediate 4a which coordinated to Ni(II) ion, and the 4N-donor set comprises both imidazole nitrogen and arylhydrazone nitrogen. The whole process is associated with loss of one hydrogen molecule and formation of one new -bond. The new compounds were characterized by elemental analysis, IR, 1H NMR, 13C NMR and HRMS data

Reaction of nitrilimines and nitrile oxides with hydrazines, hydrazones and oximes

This review article discusses the reaction of nitrilimines and nitrile oxides with hydrazines, hydrazones, and oximes. Three reaction modes were observed. The article mainly covers our work published over the last fifteen years, in which interesting heterocyles such as oxadiazoles, triazoles, and tetrazines were synthesized and fully characterized. View Full-Text Keywords

Reaction of Nitrilimines with Aromatic and Heterocyclic Ketoximes, Part 3: Synthesis of Substituted 1, 2, 4-Triazoles and 1, 2, 4, 8-Tetraazaspiro [4, 5] dec-2-enes

Nitrilimines (Za-g) react with acetophenone oxime (3) to afford 3—acyl-1-aryl-4, 5-dihydro-S-methyl-S-phenyl-1H-1, 2, 4-triazoles (4a—g). Similarly, the reaction of nitrilimines (2) with 1-methy1-4—piperidone oxime (6) gives 3-acyl-1-aryl-8-methyl-1, 2, 4, 8—tetraazaspiro [4, 5] dec-2-enes (7). Spectral data of the title compounds are discussed

Reaction of C-aroyl-N-aryl nitrilimines with selected aliphatic keto-hydrazones and keto-methylhydrazones

C-Benzoyl-and C-2-naphthoyl nitrilimines (2) react with methylhydrazones of aliphatic ketones (3, R1= CH3) to afford the cyclocondensation products 1, 2, 4, 5-tetrazines (4, 5). The reaction of simple hydrazones (3, R1= H) with the same nitrilimines gives the acyclic electrophilic addition products (6, 7), rather than the cyclocondensation tetrazine products

Synthesis of Dihydro-and Tetrahydro-1, 2, 4, 5-tetrazines from the Reaction of Nitrilimines with 1-Substituted-1-methylhydrazine

The reaction of nitrilimines (2) with 1-substituted-1-methylhydrazines (3–6) led to the formation of the respective amidrazones (7) when R = CH3, Ph, and to the acyclic adducts (8,9) when R = CHO and COCH3. The acyclic adducts underwent thermal oxidative cyclization at CH3 to give the unexpected 1,2,4,5-tetrazines (10,11). Dihydro-l,2,4,5-tetrazines (12) were also seperated when R = CHO

Metal Complexes of 6-Acetyl-4-aryl-2-ethoxycarbonyl-1, 2, 3, 4-tetrahydro-1, 2, 4, 5-tetrazine Oximes

Nitrilimines (5a-c) react with 1-ethoxycarbonyl-1-methylhydrazine (6) to give the corresponding 3-acetyl-1, 2, 4, 5-tetrazines (8a-c). Oximes of these tetrazines (9a-c) and their Pd (II)(10a) and Ni (II)(11b) complexes were prepared and characterized using IR, MS, NMR and electronic spectra

1, 2, 4-Triazoles from 1, 3-dipolar cycloaddition reaction of nitrilimines with aliphatic ketohydrazones carrying electron withdrawing groups

Alkanone and cycloalkanone hydrazones (3) carrying electron withdrawing groups (OCOCH3, COCH3, COPh) react with C-benzoyl-and C-2-naphthoylnitrilimines to give the cycloaddition triazole products (6-11). IR, 1H NMR, 13C NMR and mass spectral data are consistent with the assigned triazole ring system. Compounds (8, 9) having an acetyl group, show signal doubling in their 13C NMR spectra, apparently owing to their presence in two different mesomeric structures

Nickel (II) complexes of 3-acetyl-4, 5-dihydro-1, 2, 4-triazole hydrazones

3-Acetyl-1,2,4-triazole hydrazones (3b,c) and methylhydrazone (4d) were prepared by reacting triazoles (1b–d) with an excess of hydrazines at room temperature. Square planar nickel(II) complexes (8b,c) of (3b,c) were obtained from their reaction with Ni(OAc)2 in a 2:1 mol ratio in EtOH at room temperature. The spectral data suggest structures (8b,c) for the obtained complexes, which result from ring opening of the triazole ring followed by recyclization to give the 5-arylhydrazono-2,3-dihydro-4H-1,2,4-triazine ligand (7b,c). The reaction of triazole methylhydrazone (4d) with Ni(OAc)2 in EtOH resulted, however, in the formation of the starting triazole (1d). All new compounds were characterized by elemental analysis, i.r., 1H-n.m.r. 13C-n.m.r. and hrms

Ring transformation and complex formation of 3-acetyl-4,5-dihydro-1,2,4-triazole oximes

Abstract Oximic 1,2,4-triazole ligands 2a-e were prepared from the reaction of 3-acetyl-4,5-dihydro-1H-1,2,4-triazoles 1a-e with hydroxylamine hydrochloride at room temperature. At higher temperatures, the reaction afforded, however, the novel ring transformation product 4-amino-2-(4-chlorophenyl)-5-methyl-2H-1,2,3,6-oxatriazine 3. The reaction of the ligands 2a-e with nickel (II) and palladium (II) acetates in ethanol at room temperature yielded the respective square planar complexes 5a-e, 6a,e. X-ray structure determination of one of these complexes (5a) revealed that metallation led to unexpected ring transformation of the triazole ligand. It is probable that such ring transformation generated the imidazole-N-oxide intermediate 4a which coordinated to Ni(II) ion, and the 4N-donor set comprises both imidazole nitrogen and arylhydrazone nitrogen. The whole process is associated with loss of one hydrogen molecule and formation of one new p-bond. The new compounds were characterized by elemental analysis, IR, 1 H NMR, 13 C NMR and HRMS