Synthesis,characterization and studies of new 3‐benzyl‐4H‐1,2,4‐triazole‐5‐thiol and thiazolo[3,2‐b][1,2,4]triazole‐5(6H)‐one heterocycles

3‐Benzyl‐4‐phenyl‐1,2,4‐triazole‐5‐thiol ( 1 ) was synthesized and used as starting material for preparation of 1,2,4‐triazole bearing substituted thiosemicarbazides moiety ( 4a‐d ) in high yields. The thiosemicarbazides 4a‐d were cyclized in basic medium to give two triazole rings linked by thiomethylene group ( 5a‐d ), while cyclization of thiosemicarbazides 4a‐d with chloroacetyl chloride in the presence of CHCl₃ and K₂CO₃ afforded the thiazolidinone derivatives 6a‐d . The reaction of thiosemicarbazides 4a‐c with phenacyl bromide in the presence of EtOH and fused CH₃COONa gave the corresponding thiazoline ring systems 7a‐c . Condensation of the 3‐benzyl‐1,2,4‐triazole‐5(1H)‐thiol ( 1 ) with chloroacetic acid and aromatic aldehydes ( 8a‐ g) in boiling acetic acid/acetic anhydride mixture in the presence of fused sodium acetate gave one single isomer only, which might be 9a‐g or 10a‐g . Upon application of Micheal addition reaction on compounds 9a‐e with cyclic secondary amines such as piperidine or morpholine the 2‐benzyl‐6‐(α‐amino‐aryl/methyl)‐1,3‐thiazolo[3,2‐ b][1,2,4]‐triazol‐5‐ols ( 11a‐j ) were obtained in good yields The structure of all new compounds were determined using both spectral and elemental analyses.     

Synthesis,structure and investigations of tuberculosis inhibition activities of new 4‐methyl‐1‐substituted‐1H‐1,2,4‐triazole‐5(4H)‐thione

By the reaction aminomethylation, chloromethylation and acylation of 4‐methyl‐4H‐1,2,4‐triazole‐3‐thiol, 4‐methyl‐1‐substituted‐1H‐1,2,4‐triazole‐5(4H)‐thione 1‐8 were obtained. Molecular structure of the obtained compounds was confirmed by an elemental analysis, IR, ¹H NMR and ¹³C NMR spectra and additionally by X‐ray analysis for 2. Six new compounds 1,2,4‐7 were tested for antibacterial activity against Mycobacterium smegmatis, Mycobacterium phlei and avirulent strain Mycobacterium H₃₇Ra.     

A Novel Synthesis of 1‐Aryl‐6‐bromo‐3‐(5‐ethylthio‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐pyrazolo[4,3‐b]quinolin‐9(4H)‐ones via Thermal Cyclization of 4‐Azidopyrazoles

2‐Aryl‐hydrazononitriles 3a , 3b , 3c were prepared by coupling 3‐ethylthio‐5‐cyanomethyl‐4‐phenyl‐1,2,4‐triazole ( 1 ) with diazonium salts 2a , 2b , 2c . Reacting 3a , 3b , 3c with both ethyl bromoacetate ( 4a ) and 4‐bromobenzyl bromide ( 4b ) in DMF, in the presence of K₂CO₃, at 80 °C for 3–4 h, gave the corresponding 4‐amino‐pyrazoles 6a , 6b , 6c , 6d , 6e , 6f . Diazotization of 6a , 6b , 6c , 6d , 6e , 6f , followed by reaction with NaN₃, leads to the formation of 4‐azidopyrazoles 8a , 8b , 8c , 8d , 8e , 8f , a new heterocyclic ring system. Interestingly, fusion of 4‐azidopyrazoles 8d , 8e , 8f at temperature higher than their melting points with 5 °C for 2 min did not give the expected fused pyrazolo[4,3‐c]isoxazoles 9 but furnished instead the novel pyrazolo[4,3‐b]quinolinones 10a , 10b , 10c , in high yields.     

Synthesis and Characterization of Novel Arylaldehyde (Arylketone)‐(4‐Substituted phenyl‐5‐Substituted phenoxy‐Methyl‐4H‐1,2,4‐Triazole‐3‐yl)‐Thiol Acetyl Hydrazones

Fourteen novel arylaldehyde (arylketone)‐(4‐substituted phenyl‐5‐substituted phenoxy‐methyl‐4H‐1,2,4‐triazole‐3‐yl)‐thiol acetyl hydrazone derivatives ( 5a‐5g, 6a‐6g ) were synthesized by 4‐substituted phenyl‐5‐substituted phenoxy‐methyl‐1,2,4‐triazole‐3‐thione as starting material according to substructure link principle, followed by thioetherification, hydrazide hydrazone reaction. The structures of these compounds were confirmed by IR, ¹H NMR and elemental analysis. Crystal structure of compounds 1b and 6d were determined by the X‐ray diffraction.     

Synthesis and antimicrobial and pharmacological properties of new thiosemicarbazide and 1,2,4‐triazole derivatives

Reaction of 4‐phenyl‐4H‐1,2,4‐triazole‐3‐thione with ethyl bromoacetate has led to the formation of ethyl [(4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)sulfanyl]acetate 1 , the structure of which was confirmed by X‐ray analysis. In the next reaction with 80% hydrazide hydrate, appropriate hydrazide 2 was obtained, which in reaction with isothiocyanates was converted to new acyl derivatives of thiosemicarbazides 2 , 3 , 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h . The cyclization of these compounds in alkaline media has led to formation of new derivatives of 5‐{[(4‐phenyl‐4H‐1,2,4‐triazole‐3‐yl)sulfanyl]methyl}‐4H‐1,2,4‐triazole‐3(2H)‐thiones 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4j . The structure of the compounds was confirmed by elementary analysis and IR, ¹H‐NMR, ¹³C‐NMR, and MS spectra. Compounds 2 , 3 , 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h and 4a , 4b , 4c , 4d , 4e , 4f , 4g were screened for their antimicrobial activities, and the influence of the compounds 4a , 4b , and 4e , 4f , 4g on the central nervous system of mice in behavioral tests was examined. J. Heterocyclic Chem., (2011).     

Synthesis and antimicrobial activity of some novel substituted 1,2,4‐triazoles bearing 1,3,4‐oxadiazoles or pyrazoles

Several derivatives of substituted 1,2,4‐triazole bearing the pyrazole (or oxadiazole) ring were synthesized via the reaction of 2,4‐dihydro‐4‐benzyl‐5‐(isomeric pyridyl)‐3H‐1,2,4‐triazole‐3‐thione 1a , 1b , 1c with ethyl chloroacetate, hydrazine hydrate, and acetyl acetone (or CS₂/KOH) in absolute ethanol. The intermediate then undergoes an intramolecular cyclization in acidic medium. The newly synthesized compounds 4a , 4b , 4c to 7a , 7b , 7c were characterized using IR, NMR, and MS Spectroscopy. Some of the synthesized compounds 4 , 5 , 7a , 7b , 7c were evaluated for their antibacterial and antifungal activities. Most of these compounds indicated activity comparable to Gentamycine. Also some of them are more active than Tolnaftate, a known antifungal drug. J. Heterocyclic Chem., (2011)     

Synthesis,Characterization and Crystal Structures of new 1,2,4‐Triazole based Schiff‐bases and their Copper(I) Complexes

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, 1 ) with 4‐methoxy benzaldehyde and 3‐methoxybenzaldehyde in methanol led to the iminic derivatives 4‐(4‐methoxybenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)thione ( 2 , L1) and 4‐(3‐methoxybenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione ( 3 , L2). The reaction of the latter with [(PPh₃)₂CuCl] in methanol solution gave the first Cu^I complex of 3 , [(PPh₃)₂CuCl(L2)] ( 4 ) and in chloroform solution the complex [(PPh₃)₂CuCl(L2)]·2CHCl₃ ( 5 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for 2 at ?80 °C: space group P2₁/c with a = 1351.3(3), b = 399.4(1), c = 2225.2(5) pm, β = 96.50(2)°, Z = 4, R₁ = 0.0667, for 3 at ?80 °C: space group R3c with a = b = 3020.4(2), c = 708.2(1) pm, Z = 18, R₁ = 0.0435, for 4 at ?80 °C: space group P2₁/c with a = 1427.8(1), b = 1129.0(1), c = 2622.8(2) pm, β = 97.19(1)°, Z = 4, R₁ = 0.0517 and for 5 at ?80 °C: space group with a = 1280.5(1), b = 1316.1(1), c = 1731.4(1) pm, α = 78.14(1)°, β = 86.06(1)°, γ = 64.69(1)°, Z = 2, R₁ = 0.0525.     

Synthesis,Characterization and X‐ray Structures of AMTT‐Type Schiff bases and two CuI Complexes (AMTT= 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione)

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT) with 4‐methylbenzaldehyde and 4‐methoxybenzaldehyde in ethanol led to the iminic derivatives ‐4‐(4‐methylbenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)thione ( L1 ) and 4‐(4‐methoxybenzyl‐ideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione ( L2 ). The reaction of L1 with CuCl in the presence of triphenylphosphane as co‐ligand in methanol/chloroform solution gave the Cu^I complex containing L1 , [Cu( L1 )(PPh₃)₂Cl]·0.5CH₃OH·0.25CHCl₃ ( 1 ). Treatment of L2 with the same metal salt in a molar ratio of 1:1 in methanol and further addition of a solution of PPh₃ in chloroform led to the complex [Cu( L2 )(PPh₃)₂Cl]·2.5CHCl₃ ( 2 ). The complexes and L1 were characterized by IR and NMR spectroscopy as well as by X‐ray diffraction studies. In both complexes, the Schiff base ligand is coordinated to the copper ion through its sulfur atom. The other coordination sites around the copper ion are occupied by two triphenylphosphane molecules and one chloride ion. Therefore, each Cu^I ion is in a distorted tetrahedral environment. Crystal data for L1 at ?100 °C: space group P2₁/n with a = 720.5(1), b = 1140.6(1), c = 1426.3(2) pm, β = 91.25(1)°, Z = 4, R₁ = 0.03, for 1 at ?120 °C : space group with a = 1286.3(1), b = 1740.3(1), c = 2060.2(1) pm, α = 79.085(6), β = 83.827(5), γ = 76.688(6)°, Z = 4, R₁ = 0.0649 and for 2 at ?80 °C : space group with a = 1183.7(2), b = 1370.1(2), c = 1812.1(3) pm, α = 85.69(2), β = 88.52(2), γ = 64.89(2)°, Z = 2, R₁ = 0.0488.     

Study of the oxidation of some catechols in the presence of 4‐amino‐3‐thio‐1,2,4‐triazole by digital simulation of cyclic voltammograms

Electrochemical oxidation of catechol and its derivatives ( 1a–d ) has been studied in the presence of 4‐amino‐3‐thio‐1,2,4‐triazole ( 3 ) at various pHs. Some electrochemical techniques such as cyclic voltammetry using the diagnostic criteria derived by Nicholson and Shain for various electrode mechanisms and controlled‐potential coulometry were used. Results indicate the participation of catechols ( 1a–d ) with 3 in an intramolecular cyclization reaction to form the corresponding 1,2,4‐triazino[5,4‐b]‐1,3,4‐thiadiazine derivatives. In various scan rates, based on an electron transfer–chemical reaction–electron transfer–chemical reaction mechanism, the observed homogeneous rate constants (k_obs) for Michael addition reaction were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. The oxidation reaction mechanism of catechols ( 1a–d ) in the presence of 4‐amino‐3‐thio‐1,2,4‐triazole ( 3 ) was also studied. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 340–345, 2007     

On an Unexpected 2D‐linked Rare Earth 1,2,4‐Triazolate Network: Synthesis,Crystal Structure,Spectroscopic and Thermal Properties of $_{\infty}^{2}\rm [Ho(Tz)_{3}(TzH)_{2}]TzH$

The network compound , (Tz^? = 1,2,4‐triazolate anion, C₂H₂N₃^?, TzH = 1,2,4‐1H‐triazole, C₂H₃N₃), was obtained as pink single crystals by the reaction of the holmium metal with a melt of the amine 1,2,4‐1H‐triazole. No additional solvent was used. The compound is an unexpected example of a 2D‐linked network structure as other lanthanides give 3D‐frameworks and MOFs with 1,2,4‐1H‐triazole instead. This illustrates that the series of lanthanides yields very different results in attempts to create MOF structures. In the triazolate ligands Tz^? function both as μ‐η¹:η² linkers as well as η¹ end on ligands. The latter coordination mode is also found for additional triazole molecules. C.N. is nine for holmium(III). The layers exhibit a system of intra and inter layer hydrogen bonding and to triazole molecules from the melt reaction intercalated in‐between the layers. The product was investigated by X‐ray single crystal analysis, Mid IR, Far IR and Raman spectroscopy, and with DTA/TG regarding its thermal behaviour.     

Synthesis of Novel 3‐(3‐(5‐Methylisoxazol‐3‐yl)‐7H‐[1,2,4]Triazolo [3,4‐b][1,3,4]Thiadiazin‐6‐yl)‐2H‐Chromen‐2‐Ones

A novel series of coumarin substituted triazolo‐thiadiazine derivatives were designed and synthesized by using 5‐methyl isoxazole‐3‐carboxylic acid ( 1 ), thiocarbohydrazide ( 2 ), and various substituted 3‐(2‐bromo acetyl) coumarins ( 4a , 4b , 4c , 4e , 4d , 4f , 4g , 4h , 4i , 4j ). Fusion of 5‐methyl isoxazole‐3‐carboxylic acid with thiocarbohydrazide resulted in the formation of the intermediate 4‐amino‐5‐(5‐methylisoxazol‐3‐yl)‐4H‐1,2,4‐triazole‐3‐thiol ( 3 ). This intermediate on further reaction with substituted 3‐(2‐bromo acetyl) coumarins under simple reaction conditions formed the title products 3‐(3‐(5‐methylisoxazol‐3‐yl)‐7H‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazin‐6‐yl‐2H‐chromen‐2‐ones ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j ) in good to excellent yields. All the synthesized compounds were well characterized by physical, analytical, and spectroscopic techniques.     

Synthesis and growth regulatory activity of pyrazolesulfanyl‐ and isoxazolesulfanyl‐1H‐[1,2,4]triazoles and their azinyl derivatives

By cyclocondensation of 3‐(1H‐[1,2,4]triazol‐3‐ylsulfanyl)‐pentane‐2,4‐dion with hydroxylamine, hydrazine, methylhidrazine, and arylsulfonyl‐hydrazides, the 3‐(3,5‐dimethyl‐isoxazol‐4‐ylsulfanyl)‐1H‐[1,2,4]triazole ( 2 ) and 3‐(3,5‐dimethyl‐1‐R‐pyrazol‐4‐ylsulfanyl)‐1H‐[1,2,4]triazoles ( 3a , 3b , 3c , 3d ) are synthesized. Under the action of quaternary ammonium salts of azines with limited heating in acetone they form a series of compounds ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h ), which molecules simultaneously contain three different heterocyclic rings. Structures of compounds were confirmed by ¹H and ¹³C NMR, MS, and elemental analysis. The plants growth regulatory activities of compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h were investigated. Data of biological tests testify that these compounds can be of interest to search for new growth stimulators. J. Heterocyclic Chem., (2010).     

New N‐(Aryl)‐5‐((quinolin‐8‐yloxy)methyl)‐1,3,4‐oxa/Thiadiazol‐2‐amines and 4‐Aryl‐5‐((quinolin‐8‐yloxy)methyl)‐2H‐1,2,4‐triazole‐3(4H)‐thiones,Synthesis and Characterization

In this study, methyl 2‐(quinolin‐8‐yloxy) acetate ( 2 ) obtained by reaction of 8‐hydroxyquinoline ( 1 ) with methyl chloroacetate was condensed with hydrazine hydrate to afford the carbohydrazide ( 3 ). Thio/semicarbazide derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) were obtained by treatment of the 3 with substituted phenyl iso/thioisocyanates. The 4a , 4b , 4c , 4d , 4e , 4f , 4g on acidic and basic intramolecular cyclization led to N‐(aryl)‐5‐((quinolin‐8‐yloxy)methyl)‐1,3,4‐oxa/thiadiazol‐2‐amines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g ) and 4‐aryl‐5‐((quinolin‐8‐yloxy)methyl)‐2H‐1,2,4‐triazole‐3(4H)‐thiones ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ), respectively. All the synthesized compounds were characterized by spectroscopic techniques and elemental analyses. The thiosemicarbazide ( 4c ) was also confirmed by X‐ray crystallography.     

New 1,2,3‐triazolo[4,5‐d]1,2,4‐triazolo[3,4‐b]pyridazine derivatives II

New tricyclic 1,2,3‐triazolo‐1,2,4‐triazolo‐pyridazine derivatives, bearing a methyl substituent on the 1,2,3‐triazole ring, were prepared as potential biological agents. N‐Methylation of dimethyl 1,2,3‐triazole‐4,5‐dicarboxylate allowed synthesis of the isomeric 1‐methyl‐4,7‐dihydroxy and 2‐methyl‐4,7‐dihydroxy triazolo‐pyridazines 4a and 4b which, by a chlorination reaction, gave the corresponding 1‐methyl‐4‐chloro‐( 6a ), 1‐methyl‐7‐chloro‐ ( 6b ) and 2‐methyl‐4‐chloro‐ ( 9 ) substituted 1,2,3‐triazolo‐pyridazines. The nucle‐ophilic substitution with hydrazine hydrate and the suitable cyclization to form the 1,2,4‐triazole ring, provided the expected tricyclic isomeric derivatives 8a, 8b and 11 respectively. The p‐methoxybenzyl substituent, introduced as a leaving group to obtain either v‐triazolo‐pyridazine or v‐triazolo‐s‐triazolo‐pyri‐dazine derivatives unsubstituted on the 1,2,3‐triazole ring, appeared inadequate. Some compounds underwent binding assays toward the adenosine A₁and A_2A receptors.     

Synthesis and antimicrobial evaluation of some 1,2,4‐triazole, 1,3,4‐oxa(thia)diazole,and 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazine derivatives

3‐Methyl‐2‐benzofurancarboxylic acid hydrazide ( 2 ) reacts with carbon disulfide and pota‐ ssium hydroxide to give the corresponding potassium carbodithioate salt 3 . Treatment of the latter salt with hydrochloric acid, hydrazine hydrate, and with phen‐ acyl bromide afforded the corresponding 1,3,4‐oxadia‐ zole‐5‐thione 4 , 4‐amino‐1,2,4‐triazole‐5‐thione 5 , and thiazolidine‐2‐thione 9 derivatives, respectively. The reaction of either 1,3,4‐oxadiazole‐5‐thione 4 or 4‐amino‐1,2,4‐triazole‐5‐thione 5 with phenacyl bromide resulted in the formation of 1,2,4‐triazolo[3, 4‐b]‐1,3,4‐thiadiazine derivative 8 . Treatment of compounds 3 or 4 with hydrazonoyl halides 10a–d furn‐ ished the same 1,3,4‐thiadiazol‐2‐ylidene derivatives 11a–d . The 7‐arylhydrazono‐1,2,4‐triazolo[3,4‐ b ]‐1, 3,4‐thiadiazine derivatives 12a–d were obtained either by treatment of 4‐amino‐1,2,4‐triazole‐5‐thione 5 with hydrazonoyl halides 10a–d or by coupling of the 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazine derivative 8 with diazonium salts. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:621–627, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20162     

Synthesis of novel 1,3‐substituted 1H‐[1,2,4]‐triazole‐3‐thiol derivatives

By means of regioselective S‐alkylation of 1H‐1,2,4‐triazole‐3‐thiol ( 1 ), a series of S‐substituted derivatives 2a‐j were synthesized. In certain conditions, the reaction of 2 with arylsulfochlorides, arylisocyanates, and quaternary ammonium salts of azines corresponding compounds were obtained 1‐arylsulfonyl‐ (3a‐d) , 1‐arylcarbonamido‐ ( 4a,b ), and 1‐azinyl‐1,2,4‐ ( 6a‐p ) triazoles. Structures of compounds were confirmed by ¹H NMR and elemental analyses. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:405–410, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20565     

Synthesis,Crystal Structure,and Antibacterial Activity of 1,2,4‐Triazoles and 1,2,4‐Triazol‐3‐one

A straightforward method has been developed for the synthesis of 1,2,4‐triazol‐3‐one 3 and 1,2,4‐triazoles 6a , 6b , 6c , 6d starting from N¹‐substituted‐N¹‐tosylhydrazonates 2 and hydrazine monohydrate. This methodology affords a number of 1,2,4‐triazol‐3‐one 3 and 1,2,4‐triazoles 6a , 6b , 6c , 6d in reasonable yields. The structures of all new compounds were elucidated using infrared, ¹H and ¹³C NMR, high‐resolution mass spectrometry, elemental analysis, and the X‐ray crystallography (for compounds 3 and 6a ). Some of the newly synthesized compounds were screened for their antibacterial activity.     

Synthesis,Characterization and Crystal Structure of the Dimeric Silver(I) Complex containing 4‐Amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, 1 ) with AgNO₃ and triphenylphosphane in a molar ratio 1:1:2 in ethanol led to the dimeric complex {[Ag(AMTT)(PPh₃)₂]NO₃}₂·4EtOH ( 2 ). 2 was characterized by elemental analyses, IR, ³¹P NMR spectroscopy as well as single crystal X‐ray diffraction. Crystal data for 2 at ?80 °C: space group with a = 1265.5(2), b = 1300.9(2), c = 1509.5(2) pm, α = 83.77(2)°, β = 79.22(2)°, γ = 62.89(2)°, Z = 2, R₁ = 0.0330.     

Synthesis and Characterization of Novel 1‐Methyl‐3‐(4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐indazole Derivatives

A series of novel 1‐methyl‐3‐(4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐indazoles was synthesized in three steps from 5‐(1‐methyl‐1H‐indazol‐3‐yl)‐4‐phenyl‐2H‐1,2,4‐triazole‐3(4H)‐thiones. 5‐(1‐Methyl‐1H‐indazol‐3‐yl)‐4‐phenyl‐2H‐1,2,4‐triazole‐3(4H)‐thiones were converted into 1‐methyl‐3‐(5‐(methylsulfonyl)‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐indazoles upon methylation followed by treatment with aq. KMnO₄. The reaction of 1‐methyl‐3‐(5‐(methylsulfonyl)‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐indazoles with Raney nickel resulted in desulphonylation to afford corresponding 1‐methyl‐3‐(4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐indazoles. All the new synthesized compounds were characterized by spectral techniques.     

Synthesis and Reactions of 3‐Methylthiazolo[3,2‐a]Benzimidazole‐2‐Carboxylic Acid Hydrazide: Synthesis of Some New Pyrazole, 1,3‐Thiazoline, 1,2,4‐Triazole and 1,2,4‐Triazolo[3,4‐b]‐1,3,4‐Thiadiazine Derivatives Pendant to Thiazolo[3,2‐a]Benzimidazole Moiety

The reaction of 3‐methylthiazolo[3,2‐a]benzimidazole‐2‐carboxylic acid ethyl ester (1) with hydrazine hydrate gives the hydrazide 2 which reacts with CS₂/KOH to afford the potassium salt 3. Treatment of 3 with l‐aryl‐2‐bromoethanones 4a,b afforded the 1,3‐thiazoline derivatives 6a,b, respectively, while the reaction of 3 with hydrazine hydrate afforded 1,2,4‐triazole‐3‐thione derivative 9. The reaction of 9 with l‐aryl‐2‐bromoethanones 4a,b and with hydrazonyl chlorides 11a,b gave the 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazine derivatives 10a,b and 12a,b, respectively. Treatment of hydrazide 2 with phenyl isothiocyanate in refluxing benzene gave the thiosemicarbazide derivative 16. The latter reaction gave 1,3,4‐oxadiazole derivative 17 when benzene was replaced by DMF. Cyclization of the thiosemicarbazide derivative 16 with NaOH resulted in the formation of the 1,2,4‐triazole‐3‐thione derivative 18.