Synthesis of 2-Thio-Substituted Benzothiazoles via a Domino Condensation/S-Arylation/Heterocyclization Process

One-Pot Synthesis of Benzoxazole/Benzothiazole-Substituted Esters by Michael Addition: A Selective Construction of C-N/C-S Bonds

An efficient and convenient synthesis of benzoxazole/benzothiazole-substituted esters in a one-pot strategy is reported. In this investigation, a selective construction of C-N and C-S bonds via simple addition is performed. Thus, using substituted 2-aminophenols/2-aminobenzenethiols, TMTD (tetramethylthiuram disulfide) and α,β-unsaturated esters as starting substrates, C-N and C-S bonds can be selectively constructed by means of the Michael addition reaction. This protocol features high selectivity, high atomic economy, mild conditions, good functional tolerance and good to excellent yields, showing the potential value for the preparation of some biologically and pharmaceutically active compounds.

Metal-Free Temperature-Controlled Intermolecular [3 + 2] Annulation to Access Benzo[d]thiazole-2(3H)-thiones and Benzo[d]thiazol-2(3H)-ones

A facile access to benzo[d]thiazole-2(3H)-thiones and benzo[d]thiazol-2(3H)-ones has been developed through a temperature-controlled intermolecular [3 + 2] annulation of N,N-disubstituted arylhydrazines with CS₂ in the presence of DMSO. This protocol can obviate the prefunctionalization of the starting materials. This direct C-S/C-N bond formation reaction was performed in the absence of any external catalysts, transition metals, bases, ligands, and oxidants with high step economy.

One-Pot Synthesis of Benzoazole-Substituted Thioenamines via a Cross Dehydrogenation Coupling (CDC) Reaction

An iodine-catalyzed synthesis of benzoazole-substituted thioenamines in a one-pot manner was reported. Using 2-aminothiophenols (or 2-aminophenols or 1,2-phenylenediamines), tetramethylthiuram disulfide (TMTD), and enamines (mainly indoles) as starting materials, the target C(sp²)-S formation products (benzoazole-substituted thioenamines) could be furnished smoothly in good yields. The reaction might proceed through an electrophilic substitution pathway in a cross dehydrogenation coupling (CDC) manner. The protocol is metal-free and features easy performance, a one-pot manner, a good functional group tolerance, and good yields.

Recent advances in the synthesis of benzothiazole and its derivatives

Abstract:

Benzothiazoles have recognized pharmacophores in the field of research, predominantly in synthetic and medicinal chemistry, on account of their significant pharmaceutical properties. This important class of derivatives endows an extensive range of biological activities like anti-inflammatory, antidiabetic, anticancer, anticonvulsant, antibacterial, antiviral, antioxidant, antituberculosis, enzyme inhibitors, etc. Hence, various methodologies have been accomplished to synthesize benzothiazole compounds considering the purity, yield, and selectivity of the products. This review provides different reaction methods that are involved in the synthesis of a variety of benzothiazole derivatives.

Ag-Cu copromoted direct C2-H bond thiolation of azoles with Bunte salts as sulfur sources

A direct C2-H thiolation of azoles with Bunte salts was achieved under the combined action of copper and silver salts. This protocol could furnish various substituted 2-thioazoles in moderate to good yields. This method has a broad substrate scope and shows good functional group tolerance.

Selective C-H chalcogenation of thiazoles via thiazol-2-yl-phosphonium salts

Thiazoles and benzothiazoles undergo regioselective C2-H chalcogenation via the sequence of thiazole C2-functionalization with phosphines to produce phosphonium salts which in turn react with S- and Se-centered nucleophiles to give products of C2-H chalcogenation and allow for recovery of the starting phosphine. The atom economical sequence proceeds under mild conditions and features broad scope for both the nucleophiles (electron-rich, electron-poor, sterically hindered thiols) and the various substituted benzothiazoles. The access to the substituted medicinally relevant C2-thio benzothiazoles also enables stereoselectivity improvements in the modified Julia olefinations.

Recent Advances in Synthesis of Benzothiazole Compounds Related to Green Chemistry

Benzothiazoles have played an important role in the field of biochemistry and medicinal chemistry due to their highly pharmaceutical and biological activity. The development of synthetic processes is undoubtedly one of the most significant problems facing researchers. In this review paper, we provided recent advances in the synthesis of benzothiazole compounds related to green chemistry from condensation of 2-aminobenzenethiol with aldehydes/ketones/acids/acyl chlorides and the cyclization of thioamide or carbon dioxide (CO2) as raw materials, and the future development trend and prospect of the synthesis of benzothiazoles were anticipated.

Facile Synthesis of a Series of Non-Symmetric Thioethers Including a Benzothiazole Moiety and Their Use as Efficient In Vitro anti-Trypanosoma cruzi Agents

A series of 2-benzylsulfanyl benzothiazole (BTA) derivatives were synthesized and fully characterized and in vitro tested against two strains of T. cruzi (NINOA and INC-5), exhibiting good activities at low concentrations.

Cu(i) catalysed annulation of isothiocyanates/isocyanates with 2-iodo-sulfonamides: synthesis of benzodithiazines, benzothiadiazinones, benzothiazinylidene-anilines and benzothiazolylidene-anilines

An efficient Cu(i)-catalysed cyclisation reaction of 2-iodobenzene sulfonamides with aryl-isothiocyanates and isocyanates that affords functionalised benzodithiazines and benzothiadiazinones, respectively, has been developed. Thus, in the reaction with aryl isothiocyanates (Ar-N[double bond, length as m-dash]C[double bond, length as m-dash]S), the C[double bond, length as m-dash]S moiety participates in the cyclisation leading to a dithiazine. By contrast, in the case of aryl isocyanates (Ar-N[double bond, length as m-dash]C[double bond, length as m-dash]O), the N[double bond, length as m-dash]C part is involved in the cyclisation and a thiadiazinone is obtained. Analogous reactions of isothiocyanates with N-tosyl-2-iodo-anilines and 2-iodo-benzyl sulfonamides afford (benzothiazin-2-ylidene)anilines and (benzothiazol-2-ylidene)anilines, respectively. Probable mechanistic pathways are briefly discussed.

One-Pot Synthesis of 2-Benzyl/2-Allyl-Substituted Thiobenzoazoles Using Transition-Metal-Free Conditions in Water

A transition-metal-free protocol for the one-pot synthesis of 2-benzyl/2-allyl-substituted thiobenzoazoles in water was developed. The cyclization of 2-aminothiophenols, 2-aminophenols, and 1,2-phenylenediamines with tetramethylthiuram disulfide (TMTD) gave mercapto benzoheterocycles, and the subsequent C-S coupling with benzyl or allyl halides furnished the desired products in good to excellent yields. This method features transition-metal-free conditions with water as a solvent, an easy performance, mild reaction conditions, a wide substrate scope, and good to excellent yields, thus paving an efficient and useful way to establish a library of potentially active drug molecules.

Copper(I)-Catalyzed Tandem One-Pot Synthesis of 2-Arylthiobenzothiazoles and 2-Arylthiobenzoxazoles in Water

An efficient tandem process for the preparation of 2-arylthiobenzothiazoles has been developed. By condensation of 2-aminobenzenethiol with tetramethylthiuram disulfide (TMTD), 2-mercaptobenzothiazoles was in situ generated, which susequently underwent coupling with iodobenzenes to give the desired 2-arylthiobenzothiazoles fluently in a one-pot manner. This method can also be used for the synthesis of 2-arylthiobenzoxazoles. Inexpensive metal catalyst and ligand, mild reaction temperature, and water as solvent make this protocol practically valuable and useful in organic synthesis.

Efficient synthesis of 2-substituted azoles: radical C–H alkylation of azoles with dicumyl peroxide, methylarenes and cycloalkanes under metal-free condition

A simple and efficient synthesis of 2-substituted azoles by alkylation of azoles with dicumyl peroxide, methylarenes and cycloalkanes under metal-free condition has been developed.

Switching Selectivity of α-Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles

An operationally simple cascade protocol has been developed for the construction of 1,2- and 1,3-dithiole derivatives from α-enolic dithioesters. 1,2-Dithioles are achieved by the reaction of dithioesters with elemental sulfur in the presence of InCl₃ under solvent-free conditions. 1,3-Dithioles have been constructed via DABCO mediated self-coupling of dithioesters in open air enabling the formation of two new C-S bonds and one ring in a single operation in contiguous fashion. The reactions proceeded smoothly affording the desired sulfur-rich heterocycles in good to excellent yields, exhibiting gram-scale ability and broad functional group tolerance utilizing easy to handle cheap and easily available reagents. The probable mechanisms for the formation of 1,2- and 1,3-dithioles from α-enolic dithioesters have been suggested.

An efficient approach to construct benzisothiazol-3(2H)-ones via copper-catalyzed consecutive reaction of 2-halobenzamides and carbon disulfide

An efficient copper-catalyzed reaction for the synthesis of benzisothiazol-3(2H)-ones has been developed, starting from easily available 2-halobenzamides and carbon disulfide, which gave the corresponding target products in 30-89% yield for 25 examples. The reaction proceeds via a consecutive process with S-C bond and S-N bond formation.

Unveiling the first indole-fused thiazepine: structure, synthesis and biosynthesis of cyclonasturlexin, a remarkable cruciferous phytoalexin

The structure, synthesis, biosynthesis and antifungal activity of cyclonasturlexin, the most intriguing indolyl phytoalexin isolated from watercress plants, are reported.

Silver-mediated thio-acetoxylation and TFA triggered cyclization of amino disulfides with unactivated alkenes: synthesis of 3-aryl/alkyl-1,4-benzothiazines

A protocol for the synthesis of 3-aryl/alkyl-1,4-benzothiazines has been developed, which involves silver-mediated 1,2-thioacetoxylation of an alkene followed by cyclization using TFA.

Efficient construction of C–S and C–N bonds via metal-free reductive coupling of N-tosylhydrazones with benzo[d]thiazole-2-thiol

An efficient procedure for the synthesis of diverse benzo[d]thiazole derivatives has been developed via metal-free reductive coupling of N-tosylhydrazones with benzo[d]thiazole-2-thiols.

Recent advances in the synthesis of 2-substituted benzothiazoles: a review

Recent advances in various synthetic protocols of 2-substituted benzothiazole derivatives.