Microwave-assisted three-component synthesis of 7-aryl-2-alkylthio-4,7-dihydro-1,2,4-triazolo[1,5-a]-pyrimidine-6-carboxamides and their selective reduction

Multicomponent reactions (MCRs) and microwave-assisted organic synthesis (MAOS) have been used as key methods for the synthesis of fused dihydropyrimidine derivatives. The three-component condensation of 3-amino-5-alkylthio-1,2,4-triazoles with aromatic aldehydes and acetoacetamides under microwave irradiation was developed as a rapid and efficient solution-phase method for the high-yielding preparation of 7-aryl-2-alkylthio-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxamide libraries. In addition, the selective reduction of the formed dihydrotriazolopyrimidines to trans-trans-2-alkylthio-7-aryl-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxamides was established. The described synthetic protocols provide rapid access to novel and diversely substituted dihydroazolopyrimidine libraries.     

One-potCuAAC synthesis of (1H-1,2,3-triazol-1-yl)methyl-1,3,4/1,2,4-oxadiazoles starting from available chloromethyl-1,3,4/1,2,4-oxadiazoles

The one-pot CuAAC synthesis of (1H-1,2,3-triazol-1-yl)methyl-1,3,4-oxadiazole and (1H-1,2,3-triazol-1-yl)methyl-1,2,4-oxadiazole derivatives via three-component reaction of consequent nucleophilic substitution of chlorine, with azide, and its further “click” reaction, with alkynes, in the presence of CuI was studied. The utility of newly synthesized 2-(azidomethyl)-1,3,4/1,2,4-oxadiazoles and chloromethyl-1,3,4/1,2,4-oxadiazole derivatives was explored, and their limitations were determined. Novel 5-([4-aryl-1H-1,2,3-triazol-1-yl]methyl)-3-(aryl)-1,2,4-oxadiazoles, 2-([4-aryl-1H-1,2,3-triazol-1-yl]methyl)-5-(aryl)-1,3,4-oxadiazoles were obtained in good yields.     

Synthesis of 1,2,4- and 1,3,4-oxadiazoles from 1-aryl-5-methyl-1<Emphasis Type="Italic">H</Emphasis>-1,2,3-triazole-4-carbonyl chlorides

5-Substituted 2-(1-aryl-5-methyl-1H-1,2,3-triazol-4-yl)-1,3,4-oxadiazoles were synthesized by reaction of 1-aryl-5-methyl-1H-1,2,3-triazole-4-carbonyl chlorides with the corresponding 5-substituted 1H-tetrazoles. 5-Methyl-1-phenyl-1H-1,2,3-triazole-4-carbonyl chloride reacted with N′-hydroxybenzimidamides to give 3-aryl-5-(5-methyl-1-phenyl-1H-1,2,3-triazol-4-yl)-1,2,4-oxadiazoles. Reactions of 4-(5-methyl-1H-1,2,3-triazol-1-yl)benzoic acid with N′-hydroxybenzimidamides resulted in the formation of 3-aryl-5-[4-(5-methyl-1H-1,2,3-triazol-1-yl)phenyl]-1,2,4-oxadiazoles.     

Studies on Condensed Heterocyclic Compounds XVII. Synthesis of 6-(1-Aryl-5-methyl-1,2,3-triazol-4-yl)-3-phenyl-s-triazolo[3,4-b]-1,3,4-thiadiazoles

Treatment of 4-amino-5-mercapto-3-phenyl-1,2,4-triazole 2 with 1-aryl-4-carboxy-5-methyl-1,2,3-triazoles 1a-1j in a one-step reaction yielded several 6-(1-aryl-5-methyl-1,2,3-triazol-4-yl)-3-phenyl-s-triazolo[3,4-b]-1,3,4-thiadiazoles 3a-3j . The structures of all the products were established on the basis of elemental analyses and spectral data. The fragmentation of the mass spectra of 3a-3j under electron impact was discussed.     

v-Triazolines. Part XIX. Thiocino[4,5-d]-1,2,3-triazole and thiocino[4,5-d]isoxazole derivatives

5-Amino-2,3,6,7-tetrahydrothiocines were reacted with arylazides yielding 1-aryl-9a-amino-1,3a,4,5,7,8,9,9a-octahydrothiocino[4,5-d]-1,2,3-triazoles which could be deaminated to 1-aryl-1,4,5,7,8,9-hexahydrothiocino-[4,5-d]-1,2,3-triazoles. Similarly, the above enamines yielded, with nitrile oxides, 3-aryl-9a-amino-3a,4,5,8,9,9a-hexahydrothiocino[4,5-d]isoxazoles which were transformed with acids into 3-aril-4,5,8,9-tetrahydrothiocino-[4,5-d]isoxazoles.     

Azide based routes to tetrazolo and oxadiazolo derivatives of pyrrolobenzodiazepines and pyrrolobenzothiadiazepines

Tetrazolo- and 1,2,4-oxadiazolo-fused derivatives of the antitumour, antibiotic, DNA-interactive pyrrolo[2,1-c][1,4]benzodiazepines and their pyrrolobenzothiadiazepine derivatives have been produced as analogues of a 1,2,3-triazolo-fused pyrrolobenzothiadiazepine, which was shown to be a Glut-1 transporter inhibitor with potential as an antitumour agent. The tetrazolo-fused systems were produced by intramolecular 1,3-dipolar cycloaddition between an azide and a nitrile. The 1,2,4-oxadiazolo systems were produced by nitrile oxide cycloadditions to pyrrolobenzothiadiazepines, which were in turn produced from a 2-(azidobenzenesulfonyl)-1,2-thiazine 1-oxide. The latter species underwent a phosphite-mediated one-pot sulfur-extrusion, ring-contraction and azide to amine conversion to form 1-(aminobenzenesulfonyl)pyrroles. Bischler–Napieralski ring closure gave the pyrrolobenzothiadiazepines.     

A facile synthesis and highly atom economic 1,3-dipolar cycloaddition of hexahydropyrido[3,4-c][1,5]benzothiazepines with nitrile oxide: stereoselective formation of hexahydro[1,2,4]oxadiazolo[5,4-d]pyrido[3,4-c][1,5]benzothiazepines

A series of new 2-methyl-11-aryl-4-[(E)-arylmethylidene]-1,2,3,4,11,11a-hexahydropyrido[3,4-c][1,5]benzothiazepines were obtained by the reaction of o-aminothiophenol and (E)-1-methyl-3,5-bis(arylidene)-4-piperidones in the presence of a catalytic amount of acetic acid under solvent-free microwave irradiation. These dipolarophiles undergo a highly atom economic 1,3-dipolar cycloaddition with nitrile oxide to afford a series of novel 6-methyl-1-phenyl-8-aryl-4-[(E)-arylmethylidene]-4,5,6,7,7a,8-hexahydro[1,2,4]oxadiazolo[5,4-d]pyrido[3,4-c][1,5]benzothiazepines stereoselectively.     

Chemotherapeutical agents. VII. Synthesis and pesticidal activities of sulphides and sulphones derived from bis[4-aryl-1,2,4-triazoline-5-thione-3-yl]alkane and 5-phenyl-1,3,4-oxadiazole-2-thione

The bis[4-aryl-3-alkylthio-1,2,4-triazol-5-yl]alkanes 4 were prepared by the action of alkyl halides on bis[4-aryl-1,2,4-triazoline-5-thione-5-yl]alkanes in aqueous sodium hydroxide (5%). The prepared sulphides 4 were oxidised to give the corresponding sulphones 5 either with acidic potassium permanganate or hydrogen peroxide. Similarly, sulphides 8 were prepared from 5-phenyl-1,3,4-oxadiazole-2-thione by reaction with different alkylhalides in alkaline medium. Mannich bases 9 from 5 -phenyl-1,3,4-oxadiazole-2-thione (7) were also prepared by stirring an equimolar solution of 6 in ethanol with formaldehyde (38%) and an amine in an ice-cold bath. All the compounds were screened for their pesticidal activities but none showed any significant activity.     

Synthesis and Transformations of 2-R-5-Aryl-5,6-dihydro-7H-[1,2,4]-triazolo[5,1-b][1,3]thiazin-7-ones

A new procedure for preparation of 2-R-5-aryl-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones by condensation of 5-R-1,2,4-triazole-3-thiones with 3-arylacryloyl chlorides was developed. The thiazine ring of the [1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones is easily cleaved by treating with ammonia and hydrazine affording amides and hydrazides of 3-aryl-3-(1H-1,2,4-triazol-5-ylsulfanyl)propanoic acids. The latter react with isothiocyanates furnishing carbamoyl thiohydrazides of 3-aryl-3-(1H-1,2,4-triazol-5-ylsulfanyl)propanoic acids that in alkaline media undergo cyclization into 4-aryl-5-[2-(4H-1,2,4-triazol-5-ylsulfanyl)-2-phenylethyl]-2,4-dihydro-3H-1,2,4-triazole-5-thiones.     

Synthesis of 1H-1,2,3-triazole derivatives by the cyclization of aryl azides with 2-benzothiazolylacetonone, 1,3-benzo-thiazol-2-ylacetonitrile,and (4-aryl-1,3-thiazol-2-yl)acetonitriles

The cyclization of aryl azides with 2-benzothiazolylacetone, 1,3-benzothiazol-2-ylacetonitrile, and (4-aryl-1,3-thiazol-2-yl)acetonitriles in methanol in the presence of sodium methylate gives high yields of new products, 2-(5-methyl(amino)-1-aryl-1H-1,2,3-triazol-4-yl)-1,3-benzothiazoles and 1-aryl-(4-aryl-1,3-thiazol-2-yl)-1H-1,2,3-triazole-5-amines. 1,3-Benzothiazol-2-ylacetonitrile undergoes an anionic domino reaction with methyl 2-azidobenzoate or 2-azidobenzonitrile to give [1,2,3]triazolo[1,5-a]quinazoline derivatives. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 612–618, April, 2009.     

An efficient synthesis of 1-aryl-3-(indole-3-yl)-3-(2-aryl-1,2,3-triazol-4-yl)propan-1-one catalyzed by a Brønsted acid ionic liquid

An efficient synthesis of novel 1-aryl-3-(indole-3-yl)-3-(2-aryl-1,2,3-triazol-4-yl)propan-1-ones from indoles and 1-aryl-3-(2-aryl-1,2,3-triazol-4-yl)propan-1-one using a Br?nsted acid ionic liquid [Sbmim][HSO4] as catalyst is described. Satisfactory results with excellent yields and short reaction time were obtained in the experiments. The catalyst could be recovered conveniently and reused efficiently.     

Synthesis of novel heterocycles using 1,2,3-triazole-4-carbohydrazides as precursors

Herein, we report the synthesis of various heterocyclic ring systems containing 1,2,3-triazole from the reactions of acid hydrazides and commercially available reagents, using efficient and simple procedures. Reactions of certain 1,2,3-triazole-4-carbohydrazides and α-bromoketones in boiling ethanol afforded the corresponding hydrazones rather than the expected triazines. The hydrazones could also be synthesized in 85-90% yield via an alternative pathway that involved the reaction of 1,2,3-triazole-4-carbohydrazides and 4-acetyl-1,2,3-triazoles in boiling ethanol containing glacial acetic acid. Reaction of one of the 4-carbohydrazides with carbon disulfide, followed by the reaction with hydrazine hydrate, gave 4H-1,2,4-triazole-3-thiol in 73% yield, which further reacted with other α-bromoketones in boiling ethanol to afford 7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines in 82-84% yields. Additionally, reactions of certain carbohydrazides with ethyl 2-cyano-3,3-bis(methylthio)acrylate gave 1-aryl-1H-1,2,3-triazole-4-carbohydrazides rather than the expected 1H-pyrazole-4-carboxylates.     

Syntheses of 3-[5-Methyl-1-(4-Methylphenyl)-1,2,3-Triazol-4-yl]-6-Substituted-s-Triazolo[3,4-b]-1,3,4-Thiadiazoles

1,2,3-Triazole derivatives have been reported as inhibiting tumor proliferation, invasion, and metastasis^[1]. The fused l,3,4-triazolo[3,4-b]-1,3,4-thiadiazoles derivatives show various biological effects such as antifungal^[2], antibacterial, hypotensive and CNS depressant activities^[3]. We have reported several 6-aryl-3-[5-methyl-1-(4-methylphenyl)-1,2,3-triazol-4-yl]-s-triazolo[3,4-b]-1,3,4-thiadiazoles in the previous paper^[4]. The novel 6-aryl-3-[5-methyl-1-(4-methylphenyl)-1,2,3-triazol-4-yl]-s-triazolo[2,4-b]-1,3,4-thiadiazoles 6a-j have been synthesized by the condensation of 4-amino-5-mercapto-3-[5-methyl-1-(4-methylphenyl)-1,2,3-triazol-4-yl]-s-triazole 5 with various aromatic carboxylic acids in the presence of phosphorus oxychloride. The mercaptotriazole 5 was prepared from 4,the latter being prepared from 1 throng 2 and 3. The title compounds 6 were depicted in scheme 1. The structures of these compounds were established by elemental analysis, NMR, MS and IR techniques.     

Chemistry of 1,2,3-thiadiazole. IV. Synthesis of [1]benzoxepino-[3,4-d][1,2,3]thiadiazole, [1]benzothiepino-[3,4-d][1,2,3]thiadiazole, [1]benzoxepino[4,3-d][1,2,3]thiadiazole, [1]benzoxepino[4,3-d]oxazole and [1]benzoxepino[4,3-d]oxazole. Four novel heterocycles

Starting from the readily available 4-bromomethy-5-carbethoxy 1,2,3-thiadiazole (V), 5-bromomethy-4-carbethoxy-1,2,3-thiadiazole (IX) and ethyl 2-aryl-5-bromomethyloxazole-4-carboxylate (XIV), 4,10-dihydro-10-oxo[1]benzoxepino[3,4-d][1,2,3]thiadiazole (Ia), 4,10-dihydro-10-oxo[1]benzothiepino[3,4-d][1,2,3]thiadiazole (Ib), 4,10-dihydro-4-oxo[1]benzothiepino[4,3-d] [1,2,3]thiazole (II), 2-aryl-4,10-dihydro-4-oxo[1]benzoxepino[4,3-d]oxazoles (XIXa-XIXc) and 2-aryl-4,10-dihydro-4-oxo[1]benzothiepino[4,3-d]oxazoles (XIXd-XIXf) were prepared.     

Anodic formation of 3,6-diaryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles and 2(3-aryl-5-methyl-1H-[1,2,4]triazol-1-yl)-5-aryl-1,3,4-thiadiazoles

3,6-Disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles together with the unknown systems 2-(3-aryl-5-methyl-1H-[1,2,4]triazol-1-yl)-5-aryl-1,3,4-thiadiazoles were obtained by anodic oxidation, under aprotic conditions, of aryl aldehyde N-(5-aryl-1,3,4-thiadiazol-2-yl) hydrazones. Mechanistic proposals are given.     

Aminolysis of 2-Aryl-5-R-5,6-dihydro-7H-[1,2,4]triazolo[5,1-<Emphasis Type="Italic">b</Emphasis>]1,3]thiazin-7-ones

We have established that the products of aminolysis of 2-aryl-5-R-5,6-dihydro-7H-[1,2,4]triazolo-[5,1-b][1,3]thiazin-7-ones in boiling ethanol are 3-R-3-(5-aryl-4H-1,2,4-triazol-3-ylsulfanyl)-propanamides, and at 180°C–210°C (depending on the structure of the substituent R): 3-phenyl-4,5-dihydro-1H-1,2,4-triazoline-5-thione and 3-arylacrylamides or 3-(3-aryl-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl)propanamides. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1587–1592, October, 2005.     

3,4,5,6-Tetrafluoro-1,2-dehydrobenzene in reactions with 1,2,4-triazines

Tetrafluoro-substituted aryne, 3,4,5,6-tetrafluoro-1,2-dehydrobenzene, has been generated in situ from 2-amino-3,4,5,6-tetrafluorobenzoic acid, and its reactivity in reactions with 1,2,4-triazines as dienes has been studied. In these reactions, the corresponding azine ring transformation products, i.e., 1,2,3,4-tetrafluoro-10-(1H-1,2,3-triazol-1-yl)pyrido[1,2-a]indoles, have been obtained, in the case of triazines activated by the presence of electron-withdrawing groups, such as 6-aryl-3-(2-pyridyl)-5-cyano-1,2,4-triazines. The crystal structure of the obtained products was confirmed by X-ray diffraction analysis.     

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.     

C–H Arylation using acyl thiourea ligands: Applications in the synthesis of 3,6-diaryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles

Synthesis of a series of new 3,6-diaryl-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazoles(5a–o) was achieved by phophine free, C–H arylative cross-coupling of 6-aryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles(4a–o)with suitably substituted iodoanilines using 1-(2-naphthoyl)-3-(4-bromophenyl)thiourea as a ligand.The requisite triazolothiadiazoles(4a–o) were obtained by the condensation of 4-amino-1,2,4-triazole-3-thiol(3) with suitably substituted aromatic acids in the presence of phosphoryl chloride.     

Huisgen reaction of nitrile oxides and nitrile imines leading to isoxazoline and pyrazole-4,6-diones

Huisgen reaction of nitrile oxides and nitrile imines generated in situ in the presence of N-benzylmaleimide afforded regiospecifically the corresponding cis-3-aryl-5-benzyl-3a,4,6,6atetrahydro-4H, 6H-pyrrolo[3,4-d]isoxazoline-4,6-diones and cis-3-aryl-5-benzyl-1-(2′,4′-dibromophenyl)-3a, 4,6,6a-tetrahydro-1H,5H-pyrrolo[3,4-c]pyrazole-4,6-diones in good yield. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 935–939, June, 2006.