Synthesis and antimicrobial activities of some ethyl 2-arylthio-6-arylimidazo[2,1-b]thiazole-3-carboxylates and their sulfones

A series of new 2-arylthio-3-ethoxycarbonyl-6-arylimidazo[2,1-b]thiazoles (4a–4h) and 2-arenesulfonyl-3-ethoxycarbonyl-6-arylimidazo[2,1-b]thiazoles (5a–5h) have been prepared and characterized by analytical and spectral methods. The title compounds 4a–4h and 5a–5h were obtained by the reaction of 2-amino-4-ethoxycarbonyl-5-arylthiothiazoles (2a and 2b)/2-amino-4-ethoxycarbonyl-5-arenesulphonyl-thiazoles (3a and 3b) with various phenacyl bromides in anhydrous ethanol. These newly synthesized compounds (4a–4h and 5a–5h) were screened for their antibacterial activity against Gram-negative bacterium Escherichia coli, Gram-positive bacterium Staphylococcus aureus, and antifungal properties against Aspergillus niger and Candida albicans.     

Design,synthesis, antibacterial and antifungal activity of novel spiro-isoxazolyl bis-[5,5′]thiazolidin-4-ones and spiro-isoxazolyl thiazolidin-4-one-[5,5′]-1,2-4 oxdiazolines

The synthesis of novel isoxazolyl 1,6-dithia-4,9-diazaspiro[4.4]nonane-3,8-diones (4a–h) and isoxazolyl 1-oxa-6-thia-2,4,9-triazaspiro[4.4]non-2-ene-8-ones (5a–h) analogs is described. Reaction of N-1-\{3-methyl-5-[(E)-2-aryl-1-ethenyl]-4-isoxazolyl}-2-chloroacetamide (2) with aryl isothiocyanates yielded 3,3-methyl-5-[(E)-2-aryl-1-ethenyl]-4-isoxazolyl-2-(arylimino)-1,3-thiazolan-4-ones (3). Cyclocondensation of 3 with mercaptoacetic acid furnished novel isoxazolyl-1,6-dithia-4,9-diazaspiro[4.4]nonane-3,8-diones (4a–h). Cycloaddition of 3 with benzonitrile oxides afforded novel isoxazolyl 1-oxa-6-thia-2,4,9-triazaspiro[4.4]non-2-ene-8-ones (5a–h). Compounds 4a–h and 5a–h showed significant biological activity against all the standard strains.     

Synthesis of some new fused thiopyrano[2,3-d]thiazoles and their derivatives

A series of some new fused thiopyrano[2,3-d]thiazole derivatives have been synthesized by a stereo-selective hetero-Diels-Alder reaction of 5-(2,4-dihydroxy-benzylidene)-4-thioxo-thiazolidine derivatives 3a,b with acrylonitrile, ethyl acrylate, N-phenylmale-imide, ω-nitrostyrene and N-phenyl-1, 3, 4-triazole-2,5-dione. 5-Amino-9-hydroxy-dihydro-benzopyrano[3′,4′:4,5]thiopyrano[2,3-d]thiazol-6-one derivatives 14a,b have been synthesized by Michael addition of 3a,b with malononitrile. Structures and conceivable mechanisms are discussed.     

Synthesis and antioxidant activities of some novel fluorinated spiro[oxindole-thiazolidine] fused with sulfur and phosphorus heterocycles

Facile routes were achieved for the synthesis of novel fluorinated spiro[oxindole-thiazolidinone] fused with some sulfur and phosphorus heterocycles starting from 5-fluoro-3^′-(4-fluorophenyl)-4^′H-spiro[indole-3,2^′-thiazolidine]-2,4^′(1H)-dione (1) via its reaction with trifluoroacetamide, 2-chloro-6-fluorobenzaldehyde and hydrazine hydrate followed by treatment with some suitable sulfur and phosphorus reagents. The antioxidant activities of the synthesized compounds were also evaluated.     

Pyridine-2(1H)-thione in heterocyclic synthesis: synthesis and antimicrobial activity of some new thio-substituted ethyl nicotinate,thieno[2,3-b]pyridine and pyridothienopyrimidine derivatives

3-(4-Bromophenyl)-2-cyanoprop-2-enethioamide (1) reacted with ethyl 3-oxo-3-phenylpropanoate (2) to give ethyl 4-(4-bromophenyl)-5-cyano-2-phenyl-6-thioxo-1,6-dihydropyridine-3-carboxylate (3). Compound 3 was taken as a starting material for the synthesis of thio-substituted ethyl nicotinate derivatives 5a–d, which underwent cyclization to the corresponding thieno[2,3-b]pyridines 6a–d. Also 3 reacted with hydrazine hydrate to give the pyrazolo[3,4-b]pyridine derivative 7, which upon diazotization gave the diazonium derivative 8. Compound 6a condensed with dimethylformamide–dimethylacetal to afford thieno[2,3-b]pyridine derivative 9, which reacted with different amines 10a–e to afford the pyridothienopyrimidine derivatives 12a–e through the Dimroth rearrangement. Moreover, compound 6a reacted with different reagents to give pyridothienopyrimidine derivatives 14a and b, 17 and pyrazolothienopyridine derivative 18. In addition, acetylating compound 6c with chloroacetylchloride afforded the 3-[(2)-chloroacetylamino]thieno[2,3-b]pyridine derivative 20, which upon cyclization yielded the corresponding 2-chloromethylpyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine derivative 21. Some of the newly synthesized compounds were screened in vitro for their antimicrobial activities.

     

One pot synthesis of novel thiazolo[3,2-b][1,2,4]triazoles: A useful synthetic application of the acidified acetic acid method

Thiazolo[3,2-b][1,2,4]triazoles and some of its analogues were firstly synthesized starting from 3-benzyl-1,2,4-triazole-5-thiol (13). 3-Benzyl-1,2,4-triazole-5-thiol (13) was synthesized and reacted with aromatic ketones using the acidified acetic acid method (AcOH/H⁺) to give directly the cyclized 5-aryl-2-benzyl-1,3-thiazolo[3,2-b][1,2,4]triazoles (15a-f) rather the thioketones 14. The isomeric 2-benzyl[2,3-c]-1,2,4-triazoles 16 could not be obtained using this method. The reaction of 1-phenylacetyl-3-thiosemicarbazide (17) with phenyl bromomethyl ketones in refluxing ethanol afforded the 2-(phenylacetyl-hydrazino)-4-phenylthiazole (18) which, cyclized into 16a upon refluxing in POCl₃. The tricyclic system 20a–d was successfully prepared in one pot reaction using the acidified acetic acid in high reaction yield and short reaction time. Formation of both 15a–l and or 16a–c was assigned by the molecular minimization energy (MME) calculations which indicated that the formation of 15 is more favorable than the isomeric compounds 16. Examination of the biological activity against the selected bacteria and fungi revealed that the title compounds possess significant growth promoting effect.     

One pot solvent-free synthesis of 2H-pyrano, 2H-thiopyrano, 2H-selenopyrano[2,3-b]-1,8-naphthyridin-2-ones on solid phase catalyst under microwave irradiation

A simple and efficient procedure has been developed for the synthesis of the 2H-pyrano (3a–c), 2H-thiopyrano (5a–c), 2H-selenopyrano[2,3-b]-1,8-naphthyridin-2-ones (7a–c) by cyclisation of 2-chloro-3-formyl[1,8]naphthyridines (1a–c) with acetic anhydride under microwave irradiation using solid phase catalyst anhydrous sodium acetate. These new compounds were characterized by elemental analysis, IR, ¹H NMR and mass spectral studies.     

A general synthesis of pyridazino[4,3- e ][1,3,4]thiadiazines

A straightforward synthesis of pyridazino[4,3-e][1,3,4] thiadiazines 3(a–j) from cyclocondensation of 3,6-dichloro-4-(1-methylhydrazino) pyridazine (2) with various isothiocyanates is described.     

An efficient microwave-assisted synthesis of thieno[2,3- b ]quinolines under solvent-free conditions

A novel and efficient method for the synthesis of substituted thieno[2,3-b]quinolines has been developed. A simple one-pot reaction of 3-formyl-2-mercaptoquinolines 2a–l with 1-chloroacetone, 2-chloroacetamide, ethyl chloroacetate and 2-chloro-1-phenylethanone in presence of catalytic amount of potassium carbonate under microwave irradiation and solvent-free conditions gave thieno[2,3-b]quinolin-2-ylethanone derivatives 3a–e, thieno[2,3-b]quinoline-2-carboxamide derivatives 4a–e, ethyl thieno[2,3-b]quinoline-2-carboxylate 5a–e and phenyl(thieno[2,3-b]quinolin-2-yl)methanone derivatives 6a–e compounds respectively. The structures of all the newly synthesised compounds were elucidated on the basis of elemental analysis, IR, ¹H NMR and mass spectral data.     

The Synthesis and Characterization of s-Triazine-Cored and [Fe(III)Salen]-Capped Polymer Complexes

2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride, C₃N₃Cl₃, 1) was used as the starting material. 2-(4-Carboxyphenylamino)-4,6-dichloro-1,3,5-triazine (2) was obtained from the reaction of cyanuric chloride with 4-aminobenzoic acid in the presence of sodium bicarbonate in acetone. A mononuclear complex (4) was obtained by reacting 2 and [FeSalen]₂O (3). A series of polymeric compounds was obtained by reacting 4 with a series of diamines. The polymeric complexes were characterized by elemental analysis, AAS, FT-IR, ¹H NMR, TGA and magnetic susceptibility measurements. The complexes are low-spin, distorted octahedral Fe(III) species that are bridged by carboxylic acids. The [FeSalen]-containing compounds may have the electronic structure t_2g⁵e_g⁰. All the complexes have six coordination and are polymeric.     

Regioselective synthesis and pharmacological activities of spirodibenzo[a,d]cycloheptene-5,2′-[1,3,4]thiadiazole derivatives

Some new 3^′,5^′-substituted-5H,3^′ H-spirodibenzo[a, d]cycloheptene-5,2^′-[1,3,4]thiadiazole and 10,11-dihydro-5H,3^′ H-spirodibenzo[a, d]cycloheptene-5,2^′-[1,3,4]thiadiazole derivatives 3a–n were regioselectively synthesized under 1,3-dipolar cycloaddition of 5-thiooxo-5H-dibenzo[a, d]cyclo-heptene and 5-thiooxo-10,11-dihydro-5H-dibenzo[a, d]cycloheptene with a variety of nitrilimines (generated in situ via dehydrohalogenation of the corresponding hydrazonoyl chlorides in the presence of triethylamine). The new products were tested for antiinflammatory, analgesic, and ulcerogenic score activities comparable to Indomethacin. Compounds 3i–l showed significant activity compared to Indomethacin.     

Synthesis of 7H-Benzo [de] -s-triazolo [5,1-a] isoquinolin-7-one derivatives and study of their fluorescent properties

N-Aminonaphthalimide (4a) and N-amino-5-nitronaphthalimide (4b) prepared from acenaphthene (1a) and 5-nitroacenaphthene (1b) by oxidation, cyclization with acetic anhydride and subsequent treatment with hydrazine sulphate were reacted with a variety ofcarboxylic acid amides such as formamide, acetamide, benzamide, cinnamic amide, coumarin-3-carboxamide and urea using zinc chloride in ethanediol at 150°C to give the 10-substituted and 6-nitro-10-substituted-7H-benzo[de]-s-triazolo[5,1-a]-isoquinolin-7-ones (6a–6f and 6b–6m), respectively. Acetylation of the 10-amino derivative 6f and reductive acetylation of the 6-nitro-10-substituted derivatives 6h–6m gave the 10-acetamido, 6-acetamido-, 6-acetamido-10-methyl, 6-acetamido-10-phenyl, 6-acetamido-10-(2-styryl), 6-acetamido-10-(coumarin-3-yl) and 6,10-bisacetamido derivatives (6g, 7a–7f), respectively. The fluorescent properties of the compounds 6a–6e and 7a–7f were studied. Compounds 6a, 6b and 7e were applied as fluorescent whiteners on polyester fibres and gave satisfactory results.     

Synthesis of some new spiroheterocyclic pyrylium salts related to 1-oxa-4-thiaspiro[4.4] nonan-2-one and/or [4.5]decan-2-one as antimicrobial agents

1-Oxa-4-thiaspiro[4.4]nonan-2-one ( 1a ) and/or 1-oxa-4-thiaspiro[4.5] decan-2-one ( 1b ) were reacted with aniline and/or p-chloroaniline to afford the corresponding spirothiazolidinones ( 2a–d ). Reaction of 2a–d with chalcones gave 2-(α – paracylbenzyl)-4-aryl-1-thia-4-azaspiro[4.4]nonan-3-one and 2-(α-aracylbenzyl)-4-aryl-1-thia-4-azaspiro[4.5]decan-3-one ( 3a–p ) respectively. Compounds 3a–p were reacted with acetic anhydride and perchloric acid to yield the spiropyrano[2,3-d]thiazol[4]ium perchlorate derivatives 4a–p . The structures of the synthesized compounds were elucidated by elemental and spectroscopic ( IR and ¹H-NMR) analysis. All the prepared compounds were tested for their antimicrobial activities in comparison with tetracyclic as a reference compound.     

A facile one pot synthesis of some new 2-phenyl-2H-[1,3]thiazino[6,5-b]quinolines under microwave irradiation in solvent free conditions

A series of some new 2-phenyl-2H-[1,3]thiazino[6,5-b]quinolines have been synthesized by the one pot reaction between 2-chloro-3-formylquinolines 1a–i and thiobenzamide using p-TsOH catalyst under microwave irradiation. The procedure is simple, environmentally benign and occurs in good yields. All the new compounds were characterized by elemental analyses, IR, ¹H NMR and mass spectral data.     

Controlling the ethylene polymerization parameters in iron pre-catalysts of the type 2-[1-(2,4-dibenzhydryl-6-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl] pyridyliron dichloride

The ligand series 2-[1-(2,4-dibenzhydryl-6-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridines and the iron(II) chloride complexes thereof have been synthesized and characterized by elemental and spectroscopic analyses. The molecular structures of C1 and C2, determined by single-crystal X-ray diffraction analysis, confirmed a pseudo-square-pyramidal geometry at the iron center. Upon treatment with either MAO or MMAO, all iron pre-catalysts possessed good thermo-stability and exhibited high activities [up to 5.22 × 10⁷ g mol^?1(Fe) h^?1] toward ethylene polymerization, producing highly linear polyethylene products. Optimization of the reaction parameters gave polyethylenes with narrow molecular weight distributions, indicating that single-site active species were formed; the molecular weights of the resultant polyethylenes could also be controlled.     

A simple green synthesis of (Z)-5-arylmethylene-4- thioxothiazolidines and thiopyrano[2,3-d]thiazolidine-2-thiones in PEG-400 under catalyst-free conditions

An improved Knoevenagel condensation of various aromatic aldehydes with thiazolidine-2,4-dithione and with 4-thioxothiazolidin-4-one can be achieved at room temperature in polyethylene glycol-400 without catalyst to afford (Z)-5-arylmethylene-4-thioxothiazolidine derivatives 3a–3o. Also, the [4+2] cyloaddition reaction of 3a–3g with N-phenylmaleimide 4 gave the cycloadducts 5a–5g under the same reactions conditions. The structure of all the newly synthesized compounds was established on the basis of the elemental analysis and spectral data. This process is a simple, efficient, economical, and environmentally benign compared to classical reactions.     

Bis[4-(methylthio)phenylmethyleneaminophenyl] disulfide, 2-[4-(methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole,and its nickel(II) and cobalt(II) complexes: Synthesis,adsorption on gold surface and electrochemical characterization

2-[4-(Methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole (1) and bis[4-(methylthio)phenylmethylene-aminophenyl] disulfide (2) were synthesized. Novel coordination compounds of Ni(II) and Co(II) with 2-[4-(methylthio)phenylmethyleneamino]thiophenol, M(1)₂ (M=Co (3); M=Ni (4)), were prepared by reacting 1 with M(OAc)₂·6H₂O or MCl₂·6H₂O in EtOH solution. The structure of 2 was proved by X-ray crystallography. Electrochemical behavior of 1–4 in CH₃CN solution and at the surface of a gold electrode was studied by cyclic voltammetry. The modification of the electrode by ligand 1 and its complexes with Ni²⁺ and Co²⁺ is described in detail. Two procedures were used to obtain a self-assembled monolayer of a metal complex on the gold surface: the adsorption of prepared coordination compound 3 or 4 on the electrode and the initial modification of the electrode with ligand 1 followed by the formation of a coordination complex between the ligand adsorbed on the electrode and a metal salt occurring in solution. On the basis of the electrochemical data, it was found that the structure of complexes formed on the surface differs from that of the complexes produced in solution.     

Synthesis of [1.1.1]Propellanes by Cyclization of 3-Alkylidenecyclobutylidenes

Starting from tricyclo [3.1.0.0^2,6]hexane 5 and 1- bromobicyclo[1.1.0]butane 6 , a series of [1.1.1]propellanes 15 and 21 has been synthesized which carry alkyl, aryl, alkenyl, and alkynyl groups. Propellane formation proceeded via 1-bromo-1-chloro-3-alkylidenecyclobutanes of type 13 and 19 , which on treatment with methyllithium gave rise to the generation of carbenes 14 and 20 as short-lived intermediates. For these carbenes, the most efficient path of stabilization is obviously the intramolecular cycloaddition. Ab initio MO calculations at the Becke3LYP/6-31G* and MP2/6-31G* level of theory indicated that 3-alkylidenecyclobutylidenes 4 and 37a–d are not local energy minima but collapse to the corresponding [1.1.1]propellanes. On this basis, propellane formation should follow a carbenoid reaction path.     

3,1′-Bridged 2-[2′-(4″-dialkylaminophenyl)ethenyl] pyrylium and 1-Benzopyrylium Dyes – Synthesis and Vis/NIR Absorption/Emission Behaviour

A series of new 3,1′-bridged 2-[2′-(4″-dialkylaminophenyl)ethenyl]-4,6-diarylpyrylium perchlorates ( 3 ), 2-[2′-(4″-dialkylaminophenyl)ethenyl]-7-diethylamino-1-benzopyrylium perchlorates 5–8 , 2-[4′-(4″-dialkylaminophenyl)butadien-1′,3″-yl]-, and 2-[2′-(7″-diethylaminocoumar-3″-yl)ethenyl]-7-diethylamino-1-benzopyrylium perchlorates 10–12 were synthesized and characterized by means of elemental analysis, m.p., Vis/NIR, and ¹H NMR spectra. Semiempirical MO calculations were performed to elucidate the essential features of the chromophores. The size of the bridging ring strongly affects the geometry of the chromophores which, in turn, determines the extent of charge transfer of the longest wavelength electronic transition. Increasing deviation from planarity causes the polymethine-like chromophore to become more polyene-like.     

Synthese und 13C-NMR-Spektroskopie einiger Pyrrolo[2,1-b]chinazoline

Synthesis and ¹³C-N.M.R.-Spectroscopy of Pyrrolo-[2,1,-b]quinazoline In 6- or 7-position substituted pyrrolo-[2,1-b]quinazoline derivatives were synthesized by reacting substituted anthranilic acid derivatives with either 4-amino-butyric acid or 2-methoxy-Δ¹-pyrroline. Furthermore some at C-3 substituted desoxyvasicinone derivatives were prepared. Using these compounds and different n.m.r. spectroscopie techniques the ¹³C resonance signals of all carbon atoms in peganine were assigned.