Copper(II)- and gold(III)-mediated cyclization of a thiourea to a substituted 2-aminobenzothiazole

Benzothiazole derivatives are a class of privileged molecules due to their biological activity and pharmaceutical applications. One route to these molecules is via intramolecular cyclization of thioureas to form substituted 2-aminobenzothiazoles, but this often requires harsh conditions or employs expensive metal catalysts. Herein, the copper(II)- and gold(III)-mediated cyclizations of thioureas to substituted 2-aminobenzothiazoles are reported. The single-crystal X-ray structures of the thiourea N-(3-methoxyphenyl)-N\u27- (pyridin-2-yl)thiourea, C13H13N3OS, and the intermediate metal complexes aquabis[5-methoxy-N-(pyridin-2-yl-κN)-1,3-benzothiazol-2-amine-κN3]copper(II) dinitrate, [Cu(C13H11N3OS)2(H2O)](NO3)2, and bis{2-[(5-methoxy-1,3-benzothiazol- 2-yl)amino]pyridin-1-ium} dichloridogold(I) chloride monohydrate, (C13H12N3OS)2[AuCl2]Cl⋅H2O, are reported. The copper complex exhibits a distorted trigonal–bipyramidal geometry, with direct metal-to-benzothiazoleligand coordination, while the gold complex is a salt containing the protonated uncoordinated benzothiazole, and offers evidence that metal reduction (in this case, AuIII to AuI) is required for the cyclization to proceed. As such, this study provides further mechanistic insight into the role of the metal cations in these transformations

Acidic Brønsted Ionic Liquids Catalyzed the Preparation of 1-((Benzo[d]thiazol-2-ylamino)(aryl)-methyl)naphthalen-2-ol Derivatives 1-[(1,3-Benzothiazol-2-ylamino)(aryl)methyl]- 2-naphthol

The acidic ionic liquids, triethylammonium hydrogen sulfate ([Et3NH]HSO4), 2-pyrrolidonium hydrogen sulfate ([Hnhp]HSO4), 3-methyl-1-sulfonic acid imidazolium chloride ([Msim]Cl), and 1-methylimidazolium hydrogen sulfate ([Hmim]HSO4) catalyzed three-component condensation reaction of aromatic aldehydes, 2-aminobenzothiazole, and β-naphthol to afford corresponding 1-((benzo[d]thiazol-2-ylamino)(aryl)-methyl)naphthalen-2-ol derivatives. The inexpensive and non-toxic ionic liquids can be reused several times without noticeable loss of their activities.KEYWORDS Aldehyde, 2-aminobenzothiazole, β-naphthol, ionic liquids, catalyst, green chemistry

Speciation of chromium in waters via sol-gel preconcentration prior to atomic spectrometric determination

Thesis (Master)--İzmir Institute of Technology, Chemistry, İzmir, 2007Includes bibliographical references (leaves: 58-63)Text in English; Abstract: Turkish and Englishxii, 63 leavesChromium occurs in natural samples in two relatively stable valence states, i.e. in the form of Cr(III) and Cr(VI) species. Their concentration in natural waters is usually very low, in the order of a few .g/L. This low concentration necessitates either the use of very sensitive analytical techniques or the application of suitable preconcentration methods prior to instrumental determination. In the present study, a resin having immobilized mercapto or amino functional groups was prepared by reacting silica gel with 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, L-glutamic acid dimethyl ester, aminophenol, aminothiophenol and aminobenzothiazol for the preconcentration of Cr(III) and Cr(VI) species in waters prior to their determination by flame atomic absorption spectrometry (FAAS). Characterization of the novel sorbents were performed using scanning electron microscopy (SEM/EDS), thermo gravimetric analysis (TGA) and elemental analysis. Among the sorbents synthesized, amino sol-gel and silica amino have been shown to be efficient in terms of sorption capacity. The applicability of the new sorbents for the preconcentration of Cr(III) and Cr(VI) species in waters was examined by batch method. After pH 4, silica amino could quantitatively sorb both Cr(III) and Cr(VI) whereas amino sol-gel sorbed only Cr(III). Effect of the amount of silica amino and amino sol-gel was examined at the optimum pH. The optimum amount of silica amino for quantitative sorption was found to be 0.1 g for 20.0 mL of 1.0 mg/L Cr(III) and Cr(VI) solutions whereas that of amino sol-gel was 0.05 g for 20.0 mL of 1.0 mg/L for both species. The effect of Cr(III) and Cr(VI) concentrations on amino sol-gel and silica amino were investigated at the initial concentrations of 1.0, 10.0, 25.0 and 50.0 mg/L. Elution was realized with 2.0 M HCl, and the percent recovery values changed between 60 and 80%

Preconcentration of rare earth elements (REEs) using silica gel modified with several functional groups

Thesis (Master)--İzmir Institute of Technology, Chemistry, İzmir, 2007Includes bibliographical references (leaves: 58-63)Text in English; Abstract: Turkish and Englishxii, 70 leavesDetermination of rare earth elements (REEs) in environmental samples can be performed by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS), in addition to other spectrometric and chromatographic methods. Although these plasma-based techniques offer a good quality data for the determination of REEs, an efficient separation/preconcentration technique prior to instrumental measurements may still be required due to low concentrations and the presence of heavy matrix, in order to achieve accurate and reliable results. In this study, silica gel modified with various organic compound containing S and N functional groups was proposed as adsorbent material for preconcentration of REEs in environmental waters before ICP-MS determination. These organic compounds are (3-aminopropyl)trimethoxysilane (APTMS), (3-mercaptopropyl) trimethoxysilane (MPTMS), 2.aminophenol, 2-aminothiophenol, 2-aminobenzothiazole and L-glutamic acid dimethyl ester. It was shown that REEs can be sorbed by only APTMS and MPTMS modified silica gel quantitatively in a broad pH range (pH>3). At high REEs concentration APTMS modified silica gel (silicaamino) worked better than silica gel. Up to 10.0 mg/L, silica-amino have sorbed higher than 80% of the REEs while silica gel could sorb only 30% of them. Among the sorbents investigated silica-amino was chosen for subsequent experiments. Desorption from APTMS modified silica and silica gel was realised with 1.0 M HNO3. Spike recovery tests were performed in various water types including ultra pure water, sea water, tap water and geothermal water and were found to change between 81-110%

The 1:1 cocrystal of rac-7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxylic acid and 2-amino­benzothia­zole

In the crystal structure of the title compound, rac-7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxylic acid–2-amino­benzo­thia­zole (1/1), C8H10O5·C7H6N2S, mol­ecules of each component are linked into centrosymmetric dimers by inter­molecular N—H⋯O hydrogen bonds. These dimers are connected by O—H⋯O hydrogen bonds into a chain along the b axis. In addition, π–π inter­actions between aromatic heterocycles occur [centroid–centroid distance of 3.4709 Å and inter­planar spacing of 3.4374 Å between symmetry-related benzothia­zole ring systems

Electrosynthesis and characterization of adherent poly(2-aminobenzothiazole) on Pt-electrode from acidic solution

AbstractThe electrochemical oxidation of 2-aminobenzothiazole, 2-ABT, on Pt-electrode has been investigated using CV in HCl solutions under nitrogen atmosphere at different temperatures, different monomer concentrations and different Na2SO4 concentrations. The experimentally obtained kinetic equation was RP,E=kE [monomer]1.19 [acid]1.32 [electrolyte]1.08, which was deduced from values of the first anodic current density (ipI). A simplified mechanism for the electrochemical oxidation of 2-ABT is proposed. Activation energy, which was obtained from the experimental data, was almost same in studied parameters. This means the electrochemical oxidation mechanism for 2-ABT must be the same. The obtained polymer films are found to be thermally stable and have tubular or fibrillar elongated crystals. Different tools have been used to characterized P(2-ABT) as: 1H NMR, Uv–vis, IR spectroscopy and elemental analysis

Mechanistic Study on the Formation of Compounds from Thioureas

Formation of 2-(N-arylamino)benzothiazole takes place, when N,N′-diphenylthioureas are treated with polymer-supported tribromide or with iodine-alumina as catalyst under solvent free conditions. However, when N-substituted-N′-benzoylthioureas are treated with polymer-supported tribromide or with iodine-alumina as catalyst either under various conditions or under solvent free conditions, decomposition takes place to give the respective benzamides and thiobenzamides. Mechanistic study of the formation of these compounds is studied using DFT calculations. It is found that electron donating group at the para-position of the aryl group of benzoylthiourea favors the formation of benzamide whereas the presence of electron withdrawing group at para-position of the aryl group of benzoylthiourea, formation of thiobenzamide takes place. When the catalyst is changed to diacetoxyiodobenzene (DIB) under similar reaction conditions, benzoxazole amides are formed; expected benzothiazoles or the decomposition products are not obtained. Mechanistic study of the reaction using DFT calculation again shows that the reaction followed through carbodiimide intermediate undergoes the formation of C-O bond in benzoxazole moiety, instead of the expected C-S bond formation of benzothiazole moiety via a sequential acylation and deacylation process

A novel fluorescent "turn-on" chemosensor for nanomolar detection of Fe(III) from aqueous solution and its application in living cells imaging

An electronically active and spectral sensitive fluorescent “turn-on” chemosensor (BTP-1) based on the benzo-thiazolo-pyrimidine unit was designed and synthesized for the highly selective and sensitive detection of Fe³⁺ from aqueous medium. With Fe³⁺, the sensor BTP-1 showed a remarkable fluorescence enhancement at 554 nm (λex=314 nm) due to the inhibition of photo-induced electron transfer. The sensor formed a host-guest complex in 1:1 stoichiometry with the detection limit down to 0.74 nM. Further, the sensor was successfully utilized for the qualitative and quantitative intracellular detection of Fe³⁺ in two liver cell lines i.e., HepG2 cells (human hepatocellular liver carcinoma cell line) and HL-7701 cells (human normal liver cell line) by a confocal imaging technique

2-Amino­benzothia­zolium 2,4-dicarboxy­benzoate monohydrate

Cocrystallization of 2-amino­benzothia­zole with benzene-1,2,4-tricarboxylic acid in a mixed solvent affords the title ternary cocrystal, C7H7N2S+·C9H5O6 −·H2O, in which one of the carboxyl groups of the benzene­tricarboxylic acid is deproton­ated and the heterocyclic N atom of the 2-amino­benzothia­zole is protonated. In the crystal, inter­molecular N—H⋯O and O—H⋯O hydrogen-bonding inter­actions stabilize the packing

2-Aminobenzothiazole degradation by free and Ca-alginate immobilized cells of Rhodococcus rhodochrous

International audience2-Aminobenzothiazole (ABT) degradation was investigated using free and immobilized systems during photodegradation under solar light in the presence of Fe(III)-nitrilotriacetic acid (FeNTA), biodegradation by Rhodococcus rhodochrous, and during combined conditions. Ca-alginate hydrogel was chosen as a model matrix and some complementary studies were required to characterize this new system. R. rhodochrous metabolism in this type of environment was monitored by NMR spectroscopy. Neither change in intracellular pH values nor in ATP concentrations was observed by in vivo 31P NMR, showing that no metabolic modification occurred between free and immobilized cells. 1H NMR demonstrated that alginate was not used as carbon source by R. rhodochrous. After establishing the pre-treatment protocol by SPE to eliminate solubilised alginate, ABT adsorption on beads and degradation were studied. The same pathways of transformation were observed in suspended and immobilized cell systems. Considering the ABT adsorption phenomenon on alginate beads (8%), the efficiency of the two systems was found to be comparable although the degradation rate was slightly lower with immobilized cells. The most important result was the finding that the positive effect of FeNTA on ABT degradation with immobilized cells was similar to that observed previously with free cells. All these results show that mechanisms observed with free cells can be extrapolated to entrapped cells, i.e. under conditions much closer to those usually encountered in the environment