Synthesis of New Heterocyclic Rings Containing Benzothiazole Moiety (original) (raw)
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Journal of Enzyme Inhibition and Medicinal Chemistry, 2014
Twenty-five new N-[4-(benzothiazole-2-yl)phenyl]acetamide derivatives bearing different heterocyclic ring systems were synthesized using 2-(4-aminophenyl)benzothiazole structure as a pharmacophoric group. Final compounds were screened for their potential antitumor activity in vitro against approximately 60 human tumor cell lines derived from nine neoplastic diseases at National Cancer Institute, USA. 2-(4-Aminophenyl)benzothiazole structure was prepared by the reaction of 4-aminobenzoic acid and 2-aminothiophenol in polyphosphoric acid using microwave irradiation. After acetylation reaction, amide compounds 2a and 2b were obtained, which were then reacted with 2-mercapto(benz)imidazole/benzothiazole/ benzoxazole derivatives in acetone with the presence of potassium carbonate to gain final compounds (3-27). Among all tested compounds, compound 10, namely N-[4-(benzothiazole-2-yl)-3-chlorophenyl]-2-[(benzimidazole-2-yl)thio]acetamide, and compound 16, namely N-[4-(benzothiazole-2-yl)phenyl]-2-[(1,5-diphenyl-1H-imidazole-2-yl)thio]acetamide, were found to be of considerable anticancer activity against some cancer cell lines.
Synthesis of some biologically active benzothiazole derivatives
N-(4,5-dihydro-1H-imidazol-2-yl)-6-substituted-1,3-benzothiazol-2-amines and N-(1Hbenzimidazol-2-yl)-6-substituted-1,3-benzothiazol-2-amines were synthesized by the reaction of 6-substituted-2-aminobenzothiazoles with carbon disulphide and methyl iodide. It was followed by the reaction with o-phenylene diamine/ ethylene diamine. All the synthesized compounds were characterized by elemental analysis, IR spectra, 1H NMR and MASS spectral studies. They were screened for their anti-inflammatory, antiulcer, antitumor, entomological (antifeedant, acaricidal, contact toxicity and stomach toxicity) and antibacterial activities.
Green Synthesis, Biological Evaluation of Newer Benzothiazole Derivatives
Benzothiazole is one of the most important heterocyclic compound, weak base, having varied biological activities and still of great scientific interest now a days. They are widely found in bioorganic and medicinal chemistry with application in drug discovery. In the present study some novel benzothiazole derivatives were synthesized under green synthesis by microwave irradiation method by using Phenyliodoniumbis-trifluoroacetate (PIFA) in ethanol according to the scheme. All the synthesized benzothiazole derivatives have been characterized by using elemental analysis, FT-IR, 1HNMR, 13C NMR spectroscopy and further supported by mass spectroscopy. Purity of all the compounds has been checked on thin layer chromatographic plate and HPLC technique. All the synthesized compounds were evaluated for antimicrobial activity by estimating the minimum inhibitory concentration (MIC) by adopting serial dilution technique and analgesic activity was examined by using the hot-plate method. All the compounds exhibited moderate to significant antimicrobial and analgesic activities.
Substituted benzothiazoles: synthesis and medicinal characteristics
hc, 2013
The attractiveness of heterocyclic compounds in medicinal chemistry has increased significantly in the past few decades as they have been proven to be highly active for a number of purposes. More specifically, the benzothiazole-containing heterocyclic compounds have shown great promise in the pharmaceutical industry. As continuation of our first review article of the synthesis and specific applications of various benzothiazole cyanine dyes (Henary, M.; Paranjpe, S.; Owens, E. A. Synthesis and application of benzothiazole containing cyanine dyes. Heterocycl. Commun. 2013, 19, 1–11), we will focus in this review on the synthesis and medical applications of alternate compounds that utilize the benzothiazole scaffold as a part of their molecular structure. Benzothiazole derivatives encompass an attractive heterocyclic class that exhibits exciting medicinal properties. The applicability of these heterocyclic structures includes positron emission tomography probes for monitoring Alzheimer...
Preparation and Characterization of some new Benzothiazole-Heterocyclic Derivatives
Egyptian Journal of Chemistry
In this work new different hetero cyclic derivatives were synthesized that which including β-Lactam, teterazole and also thiazole rings.The starting material is 2-amino-6-methoxy-Benzothiazole. All these reactions follow by (TLC) and Measurement melting points for some of these derivatives. The compounds identified by FT-IR and some of them by 1H-NMR and 13C-NMR spectra., The prepared benzothiazole derivatives in this study gave good results through appearance of new bands and disapearance of other bands in formatted compounds that gave first data to formation benzothiazole derivative , while second technique represented by resonance spectra that gave also good results for formatted benzothiazole derivative.m in addition to flowing of all reactions by paper chromatography.
Synthetic access to some new benzothiazole-based 1,3,4-thiadiazole and 1,3-thiazole derivatives
TURKISH JOURNAL OF CHEMISTRY, 2016
1-(Benzothiazol-2-yl)-3-phenylthiourea 2 was prepared and treated with hydrazonoyl chlorides 3a-e to yield the corresponding 5-(benzothiazol-2-ylimino)-1,3,4-thiadiazole derivatives 6a-e, respectively. Reaction of the thiourea derivative 2 with ethyl 2-chloro-3-oxobutanoate 9 afforded the corresponding 2-(benzothiazol-2-ylimino)thiazole-5-carboxylate derivative 11. The newly synthesized heterocyclic derivatives were confirmed from their elemental and spectral analyses.
Synthesis and study of new antimicrobial benzothiazoles substituted on heterocyclic ring
Arkivoc, 2008
New 2-styryl benzothiazolium salts substituted on the heterocyclic ring have been synthesised by the condensation of 3-alkyl-2-methylbenzothiazolium halides with 4-substituted benzaldehydes. The intramolecular charge transfer from the electron-donor substituent to the benzothiazolium ring is a typical feature of the prepared compounds. This type of benzothiazolium derivatives can be used as pharmaceutical substances as well as compounds with nonlinear optical response. Antimicrobial in vitro activity was determined and the influence of substituents has been evaluated. The substituents on the heterocyclic ring in positions 5 and 6 do not increase the biological activity significantly.
Synthesis, Characterization and Biological Activity of Various Substituted Benzothiazole Derivatives
2010
A series of 2-(benzo[d]thiazol-2-ylthio)-N-(2-oxoindolin-3-ylidene)acetohydrazide (3a-3g), 2-(benzo [d]thiazol-2-ylthio)-N-(2,4'-dioxospiro[indolin-3,2'-thiazolidin)-3'yl)acetamide (4a-4g) and 2'-((benzo[d]thiazol-2-ylthio)methyl)spiro[indoline-3,5'thiazolo[4,3-b][1,3,4]oxadiazol]-2-ones (5a-5g) have been synthesized and screened for their anti-inflammatory, analgesic and antibacterial activities. The most potent antiinflammatory and antibacterial compound of this series was compound 5d and most potent analgesic compound was compound 5e. Structures of all the compounds were established by elemental and spectral (IR and 1 H NMR) analysis.
Synthesis and cyclization of benzothiazole: review
Benzoheterocycles such as benzothiazoles, benzimid azoles and benzoxazoles can serve as unique and versatile scaffolds for experimental drug design. Among the all benzohaterocycles, benzothiazole has considerable place in research area especially in synthetic as well as in pharmaceutical chemistry because of its potent and significant pharmacological activities. Since, a wide range of methods are available for synthesizing benzothiazole nucleus and its derivatives but a real need exists for new procedures that support many kinds of structural diversity and various substitution. The present review deals with the common methods adopted and reported to focus the synthesis as well as cyclisation of benzothiazole nucleus. INTRODUCTION Benzothiazole is a privileged bicyclic ring system. Due to its potent and significant biological activities it has great pharmaceutical importance; hence, synthesis of this compound is of considerable interest. The small and simple benzothiazole nucleus if present in compounds involved in research aimed at evaluating new products that possess interesting biological activities. 2-substitued benzothiazole has emerged in its usage as a core structure in the diversified therapeutically applications. The studies of structure–activity relationship interestingly reveal that change of the structure of substituent group at C-2 position commonly results the change of its bioactivity. Among those 2-substituted benzothiazole derivatives with fluorine substituted molecules have already received considerable attention due to their potential bioactivities (Jian Haoa et al.; 2007). Since most of the benzothiazole derivatives were reported for their diversified activity viz., antitumor, antitubercular, antimalarial, anticonvulsant, anthelmintic, analgesic, antiinflammatory, antifungal, a topical carbonic anhydrase inhibitor and an antihypoxic (Hutchison et al., 2003; Latrofa et al., 2005; Yoshida et al., 2005; Latrofa et al., 2005; Caryolle et al., 1990) In 1887, 2 substituted benzothiazole was first synthesized by A. W. Hofmann then because of diversified activity as well as simple cyclization mechanism number of synthetic routes have been adopted and reported. 2-substitutedbenzothiazoles are most commonly synthesized via one of two major routes: the most common direct method involves the condensation of an ortho-amino thiophenol with a substituted aromatic aldehyde, carboxylic acid, acyl chloride or nitrile. This method, however, is often not appropriate for manysubstituted 2-arylbenzothiazoles due to the difficulties encountered in the synthesis of the readily oxidisable 2-amino thiophenols bearing substituent groups. The other methods used extensively in the laboratories which are based on the potassium ferricyanide (Jacobsen cyclization) radical cyclization of thiobenzanilides which involve cyclization onto either carbon atom ortho to the anilido nitrogen produces only one product, hence, the Jacobsen cyclization is a highly effective strategy for benzothiazole synthesis e.g. for the synthesis of 6- substituted benzothiazoles, radical cyclization of the 3-fluoro- or 3,4-difluoro-substituted thiobenzanilides (Ben-Alloum et al., 1997). A similar mixture of regioisomeric products from the Jacobsen cyclization has also been observed by Roe and Tucker for the synthesis of 5- and 7-fluoro-2-phenylbenzothiazoles (Roe et al., 1965). A regiospecific synthesis of 2-arylbenzothiazoles unsubstituted in the phenyl ring was developed through the use of a bromo substituent ortho to the anilido nitrogen and formation of a benzyne intermediate followed by intramolecular cyclization. A similar strategy has been developed for the synthesis of wide range of 7-substituted benzothiazoles via directed ortho metallation followed by benzyne formation and subsequent cyclization (Stanetty et al 1996). These strategies, however, were found to be incompatible with the nitro functionality on the aryl ring and do not represent a general route to functionalised 2- arylbenzothiazoles (Hutchinson et al., 2000; Shi et al., 1996). CONCLUSION Benzothiazole belongs to an important class of heterocyclic compounds and exhibits a wide range of biological properties and due to its potent activities, thus the synthesis of benzothiazole is an area of current interest. Several methods for the synthesis and cyclization of benzothiazole have been reported such as Hofmann Method Jacobson synthesis and oxidation by bromine, sulphuric acid, benzyltrimethylammoniumtribromide, copper and palladium, chloroformamidium salt, Appel's salt to facilitate formation of the thiyl radical from the thiobenzamide, which cyclizes with loss of a hydrogen atom and Baker's yeast cyclization to produce the benzothiazole. Since, individual method has their own advantages and disadvantages, but the most common classical methods for the synthesis of benzothiazole are based on cyclization of thiobenzamides (Jacobson synthesis) which involves the use of potassium ferricyanide with sodium hydroxide and cyclization of substituted aniline in the presence of potassium thiocyanate achied through oxidation by bromine. The cyclization as well as structural elaboration in lead optimization, the points of attachment on the benzoheterocycle can be through a number of atoms on either the benzene or heterocyclic rings. In general, the formation of heteroatom linkages between any points on the benzoheterocyclic nucleus for example, any aromatic, lipid-like, peptide, heterocyclic or even carbohydrate appendage may take advantage of S, and N nucleophilicity. However, the formation of carbon–carbon bonds to the benzoheterocyclic nucleus from these appendages may be more involved, particularly in the presence of sensitive heteroatom functionality on the heterocyclic portion of the nucleus