Derivatives of 4-amino-4H-1,2,4-triazole-3-thiols linked to the pyrrole cycle and some products of their S-alkylation

This study offers an access to 21 new heterocyclic compounds representing pyrrole derivatives of 4-amino-4H-1,2,4-triazole-3-thiols or 1,3,4-oxadiazole-2-thiols. The principal synthetic approach is based on the cyclization of substituted potassium 2-(pyrrolecarbonyl)hydrazine-1-carbodithionate with hydrazine hydrate to 5-(substituted pyrrolyl)-4-amino-4H-1,2,4-triazole-3-thiols, followed by S-alkylation with methyl iodide or benzyl chloride. Among the resulted thirteen S-alkyl derivatives, five 1,3,4-oxadiazole derivatives have been isolated as secondary products and their formation is explained as being the result of S-alkylation of intermediate 1,3,4-oxa-diazole-2-thiols, generated in the alkaline medium. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 383–391, March, 2007.     

Synthesis and antioxidant properties of organosulfur and organoselenium compounds derived from 5-substituted-1,3,4-oxadiazole/thiadiazole-2-thiols

Organosulfur and organoselenium compounds were synthesized in good yields through reaction with 5-aryl-1,3,4-oxadiazole/thiadiazole-2-thiols and α-chloromethyl arylselenides or 4-(chloromethyl)-2-methylthiazole/2-(chloromethyl)-5-phenyl-1,3,4-oxadiazole. The obtained compounds were characterized by NMR and mass spectroscopy and screened for in vitro antioxidant activity as reflected by free radical scavenging against 2,2-diphenyl-2-picrylhydrazyl (DPPH) and reduction of molybdenum (VI) to molybdenum (V). The compounds have significant antioxidant properties in both applied methodologies.     

Synthesis of heterocycles based on arylation products of unsaturated compounds: XVII. Arylation of 2-acetylfuran and synthesis of 3-R-6-(5-aryl-2-furyl)-7<Emphasis Type="Italic">H</Emphasis>-[1,2,4]triazolo[3,4-<Emphasis Type="Italic">b</Emphasis>][1,3,4]thiadiazines

Reaction of 2-acetylfuran with arenediazonium chlorides under Meerwein reaction conditions led to the formation of 5-aryl-2-acetylfurans. The bromination of these compounds gave 2-bromo-1-(5-aryl-2-furyl)-ethanones that reacted with 4-amino-4H-5-R-1,2,4-triazole-3-thiols to form 3-R-6-(5-aryl-2-furyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines.     

Synthesis of heterocycles from arylation products of unsaturated compounds: XVIII. 5-Arylfuran-2-carboxylic acids and their application in the synthesis of 1,2,4-thiadiazole, 1,3,4-oxadiazole,and [1,2,4]triazolo[3,4-<Emphasis Type="Italic">b</Emphasis>][1,3,4]thiadiazole derivatives

Arylation of furan-2-carboxylic acid or its methyl ester with arenediazonium chlorides in the presence of copper(II) chloride gave the corresponding 5-arylfuran-2-carboxylic acids or methyl 5-arylfuran-2-carboxylates. 5-Arylfuran-2-carbonyl chlorides reacted with potassium thiocyanate and then with 5-methyl-1,2-oxazol-3-amine to give 5-aryl-N-[3-(2-oxopropyl)-1,2,4-thiadiazol-5-yl]furan-2-carboxamides as a result of recyclization of intermediate isoxazolylthiourea derivatives. The reactions of 5-arylfuran-2-carbonyl chlorides with 5-(2-furyl)-1H-tetrazole involved opening of the tetrazole ring with elimination of nitrogen molecule and led to the formation of 2-(5-arylfuran-2-yl)-5-(2-furyl)-1,3,4-oxadiazoles. 3-Substituted 6-(5-arylfuran-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles were obtained by condensation of 5-arylfuran-2-carboxylic acids with 5-substituted 4-amino-4H-1,2,4-triazole-3-thiols in phosphoryl chloride.     

Synthesis of substituted 4-([1,2,4]triazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]-[1,3,4]thiadiazol-6-yl)quinolines

4-Amino-5-R¹-4H-1,2,4-triazole-3-thiols react with 2-R²-6-R³-quinoline-4-carboxylic acids in phosphoryl chloride to give 2-R²-6-R³-4-(3-R¹-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-6-yl)quinolines.     

Synthesis of 3-Alkyl-6-aryl(arylamino)-7H-[1,2,4]triazolo- [3,4-b][1,3,4]thiadiazines

Starting from 5-alkyl-4-amino-4H-1,2,4-triazole-3-thiols and substituted chloroacetanilides, the corresponding (5-alkyl-4-amino-4H-1,2,4-triazol-3-ylsulfanyl)acetanilides were synthesized. The products underwent intramolecular cyclization in boiling phosphoryl chloride to afford 3-alkyl-6-arylamino-7H-[1,2,4]-triazolo[3,4-b][1,3,4]thiadiazines. 3-Alkyl-6-aryl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine hydrobromides were obtained by reaction of 5-alkyl-4-amino-4H-1,2,4-triazole-3-thiols with substituted phenacyl bromides.     

7β-[2-(2-氨噻唑-4-基)-(Z)-2-甲氧亚胺乙酰胺基]-3-杂环硫亚甲基头孢菌素衍生物的半合成及抗菌活性

通过5-取代-1,3,4-噁二唑-2-硫醇(2a～2h), 5-芳胺基-1,3,4-噻二唑-2-硫醇(2i～2j)和头孢菌素母体7-氨基头孢烷酸(7-ACA)反应, 制得头孢菌素中间体3a～3j, 用氨噻唑肟活性酯4和头孢菌素中间体缩合, 合成了头孢菌素衍生物5a～5j. 体外抗菌结果表明头孢菌素衍生物对革兰氏阳性菌和阴性菌均有显著抑制活性, 对金黄色葡萄球菌尤为敏感     

Alkylation,amino(hydroxy)methylation,and cyanoethylation of 5-substituted 4-phenyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole-3-thiols

Reactions of 1,2,4-triazole-3-thiols with 2-bromopropionic acid, 2-bromocaproic acid, ethylene chlorohydrine, chloroacetamide, 3-bromo-4-methoxybenzyl chloride, 2-methoxy-5-acetylbenzyl chloride, and 2-(2-chlorophenoxy)ethyl chloride in the presence of KOH have afforded new 3-sulfanyl-1,2,4-triazoles in high yields. Aminomethylation of 1,2,4-triazole-3-thiols in the presence of formaldehyde has given the corresponding 2-aminomethyl-2H-1,2,4-triazole-3(4H)-thiones. Interaction of triazole-3-thiols with formalin and acrylonitrile has resulted in the formation of N²-hydroxymethyl- and 3-(2-cyanoethyl)sulfanyl derivatives.     

Inorganic base-catalyzed formation of antivirally active N-substituted benzamides from α-amido sulfones and N-nucleophile

Background

Heteronucleophiles as well as carbanionic reagents can be used to react with α-amido sulfones, thus giving the opportunity to prepare a large array of amino derivatives. Since, novel 1,3,4-oxadiazole-2-thiol derivatives can serve as potent nucleophiles, we employed 5-subsititued phenyl-1,3,4-oxadiazole-2-thiols as the nucleophilic source of nitrogen in the reaction with α-amido sulfones.

Results

A series of N-substituted benzamides bearing 1,3,4-oxadiazol unit were prepared for the first time by the reaction of in situ generated protected imine from α-amido sulfones with 5-subsititued phenyl-1,3,4-oxadiazole-2-thiols as the source of nitrogen nucleophile. Some of the synthesized products displayed favourable antiviral activity against cucumber mosaic virus (CMV) in preliminary antiviral activity tests. The title compounds 5c, 5o and 5r revealed curative activity of 42.2%, 48.7% and 40.5%, respectively against CMV (inhibitory rate) compared to the commercial standard Ningnanmycin (53.4%) at 500 μg/mL.

Conclusion

A practical synthetic route to N-benzoyl-α-amido sulfones by the reaction of 5-subsititued phenyl-1,3,4-oxadiazole-2-thiols as the source of nitrogen nucleophiles with in situ generated protected imine from N-benzoyl-α-amido sulfones is presented. The reaction catalyzed by an inorganic base has considerable significance to exploit the potential of α-amido sulfones in organic synthesis.     

Intramolecular cyclization of 4-amino-3-alkylsulfanyl-1,2,4-triazoles as a method for annelation of thiadiazine and thiadiazole rings

4-Amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiols reacted with N-substituted isatins to give 2-oxo-3-[5-(pyridin-4-yl)-3-sulfanyl-4H-1,2,4-triazole-4-ylimino]-2,3-dihydro-1H-indoles which were treated with phenacyl bromides to obtain the corresponding S-phenacyl derivatives. The latter underwent base-catalyzed intramolecular cyclization with formation of 6,7-dihydro-5H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazines spiro-fused to 2-oxo-2,3-dihydro-1H-indole fragment at C³. Analogous cyclization of 2,6-di-tert-butyl-4-[5-hetaryl-3-(2-aryl-2-oxoethylsulfanyl)-4H-1,2,4-triazole-4-ylimino]cyclohexa-2,5-dienones involved the imino nitrogen atom to produce the corresponding 6-aroyl-5-(3,5-di-tert-butyl-4-hydroxyphenyl)-3-hetaryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles.     

Synthesis and reactions of 3-(3-ethoxycarbonyl-1-phenyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-4-yl)propenic acid

The reaction of ethyl 4-formyl-1-phenyl-1H-pyrazole-3-carboxylate with the malonic acid led to the formation (2E)-3-(3-ethoxycarbonyl-1-phenyl-1H-pyrazol-4-yl)propenic acid. In reactions of this acid chloride with 4-amino-5-aryl(hetaryl)-4H-1,2,4-triazole-3-thiols were obtained ethyl 4-[(E)-2-{3-aryl(hetaryl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-6-yl}ethenyl]-1-phenyl-1H-pyrazoe-3-carboxylates, with 5-aryltetrazoles, ethyl 4-[(E)-2-(5-aryl-1,3,4-oxadiazol-2-yl)-ethenyl]-1-phenyl-1H-pyrazole-3-carboxylates, with 1-(2-hydroxy-3,5-dimethylphenyl) followed by the Baker-Venkataraman rearrangement and the cyclization, ethyl 4-[(E)-2-(6,8-dimethyl-4-oxo-4Hchromen-2-yl)ethenyl]-1-phenyl-1H-pyrazole-3-carboxylate.     

Palladium-catalyzed asymmetric tandem allylic substitution using chiral 2-(phosphinophenyl)pyridine ligand

Palladium-catalyzed asymmetric tandem allylic substitution of (Z)-1,4-diacyloxy- and (Z)-1,4-bis(alkoxycarbonyloxy)-2-butene (2a-c) using 2-(phosphinophenyl)pyridine 1 as chiral ligand provided optically active six-membered 2-vinyl-1,4-diheterocyclic compounds with good to high enantioselectivity. For example, the reactions with catechol, 2-(benzylamino)phenol, or 1,2-bis(benzylamino)ethane as a nucleophile gave 2-vinyl-1,4-benzodioxane (71% ee), 4-benzyl-2-vinyl-1,4-benzoxazine (86% ee), and 1,4-dibenzyl-2-vinylpiperazine (86% ee), respectively.     

A facile one-pot synthesis of Nα-Z/Boc-protected S-linked 1,3,4-oxadiazole tethered peptidomimetics

A new class of S-linked 1,3,4-oxadiazole-tethered N^α-protected peptidomimetics is designed and synthesized by a reaction of N^α-Z/Boc-protected 1,3,4-oxadiazole-2-thiol with α-bromo ester derived from amino acid. The protocol has also been employed for the synthesis of glycosylated amino acids and N,N′-orthogonally protected dipeptidomimetics bearing S-linked 1,3,4-oxadiazole mimetics as well. The intermediate 5-alkyl amino-1,3,4-oxadiazole-2-thiols have been isolated as stable compounds. Further, the chain extension at both N- and C-termini of N-protected S-linked 1,3,4-oxadiazole tethered dipeptidomimetics was also demonstrated.     

Drug resistance modulation in Staphylococcus aureus, a new biological activity for mesoionic hydrochloride compounds

Two salts of the mesoionic compounds 1,4-diphenyl-5-(5-nitro-2-furanyl)-1,3,4-thiadiazolium-2-thiol chloride (MC-1) and 4-phenyl-5-(5-nitro-2-furanyl)-1,3,4-thiadiazolium-2-phenylamine chloride (MC-2) were synthesized utilizing 1,4-diphenyl-thiosemicarbazide and 5-nitro-2-furoyl chloride as starting materials. Their structures were characterized by IR, 1H-NMR, 13C-NMR and elemental analysis. These compounds were analyzed for their influence on the effectiveness of norfloxacin, tetracycline, and erythromycin (standard antibiotics) against resistant strains of Staphylococcus aureus. MC-1 and MC-2, at sub-inhibitory concentrations of 16 μg/mL, favourably modulated the antibiotic activity of tetracycline by 16- and 32-fold, respectively (MIC), and that of erythromycin by 4-fold.     

Synthesis of some new 4,5-substituted-4H-1,2,4-triazole-3-thiol derivatives

In this study appropriate hydrazide compounds, furan-2-carboxylic acid hydrazide (1) and phenylacetic acid hydrazide (2) were converted into 1,4-substituted thiosemicarbazides 4a-e and 5a-e and 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The 1,4-substituted thiosemicarbazides were then converted into 5-(furan-2-yl or benzyl)-4-(aryl)-4H-1,2,4-triazole-3-thiols 8a-e and 9a-e. In addition, the azomethines 11a-d and 12a-d were prepared from the corresponding arylaldehydes and the 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The structures of all the synthesized compounds were confirmed by elemental analyses, IR, (1)H-NMR and(13) C-NMR spectra.     

Synthesis and biological evaluation of some new substituted benzoxazepine and benzothiazepine as antipsychotic as well as anticonvulsant agents

Various 2-((2-((5-benzylideneamino)-1,3,4-oxa/thiadiazol-2-yl)methyl)hydrazinyl) methyl)benzo[b][1,4]oxa/thiazepin-4(5H)-ones (4a–4l), 2-((2-((5-(4-oxo-2-substitutedphenyl thiazolidin-3-yl)-1,3,4-oxa/thiadiazol-2-yl)methyl)hydrazinyl)methyl)benzo [b] [1,4]oxa/thiazepin-4(5H)-ones (5a–5l) and 2-((2-((5-(3-chloro-2-(substitutedphenyl)-4-oxoazetidin-1-yl)-1,3,4-oxa/thia diazol-2-yl)methyl)hydrazinyl)methyl)benzo[b][1,4]oxa/thiazepin-4(5H)-ones (6a–6l) have been synthesized. The structures of these compounds have been established by elemental (C, H, N) and spectral (IR, ¹H-NMR and Mass) analysis. The synthesized compounds were screened for their antipsychotic and anticonvulsant activities. Compound 5l was found to be the most active compound of this series.     

Synthesis and biologic properties of new thiazolylbenzodioxane derivatives

Reaction of 4-(1,4-benzodioxan-2-yl)thiazol-2-amine with acid chlorides afforded N-substituted amides which further were reduced into the corresponding amines. A new method was developed of preparation of 2-acetyl-1,4-benzodioxane, the initial compound in the synthesis of thiazolylbenzodioxane and numerous derivatives of this series. The adreno- and sympatholytic as well as antihypoxic effect of the obtained biheterocyclic 1,4-benzodioxane derivatives were investigated.     

Synthesis of new 4-amino-5-(1,4-benzodioxan-2-yl)-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole-3-thiol derivatives

Acylation and cyclization reactions of 4-amino-5-(1,4-benzodioxan-2-yl)-4H-1,2,4-triazole-3-thiol were studied. Acylation of the title compound with substituted benzoyl chlorides gave the corresponding amides, whereas its reactions with substituted benzoic acids in the presence of POCl3 were accompanied by cyclization with formation of triazolothiadiazoles containing a 1,4-benzodioxane substituent. 4-Amino-5-(1,4-benzodioxan-2-yl)-4H-1,2,4-triazole-3-thiol reacted with substituted benzaldehydes to afford the corresponding Schiff bases, and its alkylation with chloroacetic acid in ethanol in the presence of sodium acetate gave S-ethoxycarbonylmethyl derivative.     

Synthesis of a new class of azathia crown macrocycles containing two 1,2,4-triazole or two 1,3,4-thiadiazole rings as subunits

A series of new 1,2/1,3-bis[o-(N-methylidenamino-5-aryl-3-thiol-4H-1,2,4-triazole-4-yl)phenoxy]alkane derivatives 3a-d and bis[o-(N-methylidenamino-2-thiol-1,3,4-thiadiazole-5-yl)phenoxy]alkanes 6a-c were prepared by condensation of 4-amino-5-(aroyl)-4H-1,2,4-triazole-3-thiols 2a-b or 2-amino-5-mercapto-1,3,4-thiadiazole with bis-aldehydes 1a-c. Further reaction of compounds 3a-d and 6a-c with dibromoalkanes afforded the new macrocycles 5a-f and 8a-d. The cyclization does not require high dilution techniques and provides the expected azathia macrocycles in good yields, ranging from 55% to 68%.     

Synthesis of formazans from Mannich base of 5-(4-chlorophenyl amino)-2-mercapto-1,3,4-thiadiazole as antimicrobial agents

5-(4-Chlorophenyl amino)-2-mercapto-1,3,4-thiadiazole (I) was refluxed with formaldehyde and ammonium chloride in ethanol yielding the Mannich base 5-(4-chloro phenyl amino)-3-aminomethyl-2-mercapto-1,3,4-thiadiazole (II). Esterification with 4-chloro-(2,6-dinitro phenoxy)-ethyl acetate (III) under anhydrous conditions gave the intermediate (IV). Subsequent hydrazinolysis with hydrazine hydrate gave the corresponding hydrazide 3-amino methyl-5-(4-chloro phenyl amino)-2-mercapto-4′-(2′,6′-dinitro phenoxy)-acetyl hydrazide (V). The hydrazide was converted into the Schiff bases (VI_a–b) by reacting with 2-chlorobenzaldehyde and 3-methoxy-4-hydroxy benzaldehyde in presence of methanol containing 2–3 drops of acetic acid. Diazotisation with aromatic amines, sulphanilic acid and sulphur drugs gave the formazans (VII_a–g) respectively. Chemical structures have been established by elemental analysis and the spectral techniques of FTIR, ¹H NMR and mass. Antimicrobial activity (in vitro) was evaluated against the two pathogenic bacterial strains. Escherichia coli and Salmonella typhi, three fungal strains Aspergillus niger, Penicillium species and Candida albicans. The compounds have shown moderate activity.