Synthesis ofN-Substituted-2-Aminobenzothiazoles by Ligand-Free Copper(I)-Catalyzed Cross-Coupling Reaction of 2-Haloanilines with Isothiocyanates

Phenanthroline-Decorated Covalent Organic Framework for Catalytic Synthesis of 2-Aminobenzothiazoles in Water

2-Aminobenzothiazoles are widely used in the fields of pharmaceuticals and pesticides. Herein, we report a metal-free protocol for the preparation of 2-aminobenzothiazoles by a covalent organic framework (COF) catalyzed tandem reaction. In the presence of catalytic amount of phenanthroline-decorated COF (Phen-COF), a variety of 2-aminobenzothiazoles are obtained in excellent yields by the cross-coupling of 2-iodoanilines with isothiocyanates at room temperature in water. In addition, the COF-catalyst is very stable and can be reused at least seven times without loss of its catalytic activity.

Control of selectivity in the preparation of 2-substituted benzoazoles by adjusting the surface hydrophobicity in two solid-based sulfonic acid catalysts

A series of metal-free tandem reactions for the synthesis of pharmaceutically important 2-substituted benzoazoles from isothiocyanates and 2-aminothiophenol under catalyst-free conditions in the presence of Et-PMO-Me-PrSO₃H (1a) and SBA-15-PrSO₃H (1b) as solid acids were carried out in a highly selective way under solvent free conditions. A significant selectivity changeover toward either 2-mercaptobenzoxazole or 2-aminobenzoazole derivatives could be achieved by changing the employed catalyst from the relatively hydrophobic material 1a to the more hydrophilic catalyst 1b. This simple experimental procedure with a novel selective approach toward benzoazoles accompanied by green and reusable catalysts could be considered as an alternative to the existing methods for the synthesis of 2-substituted benzoazole derivatives.

One-Pot Synthesis of N,N-Diphenyl-2-benzothiazolamines from 1-(2-Iodophenyl)-3-phenylthioureas and Iodobenzenes

An efficient copper-catalyzed synthesis of a variety of N,N-diphenyl-2-benzothiazolamines was developed. Starting from substituted 1-(2-iodophenyl)-3-phenylthioureas and substituted iodobenzenes, the reaction proceeded smoothly via a tandem manner in the presence of CuI to afford the corresponding N,N-diphenyl-2-benzothiazolamine derivatives with good functional group tolerance. The protocol features simple performance, easily available starting materials, a one-pot manner, and good functional group tolerance, providing a practical strategy for the preparation of poly-functionalized amines.

Dioxygen-triggered oxidative cleavage of the C-S bond towards C-N bond formation

Research on the cleavage of C-C bonds has been well developed. By comparison with this, the activation of C-S bonds remains challenging. Herein, dioxygen-triggered oxidative cleavage of C-S bonds has been achieved, delivering a series of N-containing heterocyclic compounds that are frequently found in pesticides and pharmaceuticals. Additionally, the potential utility of this protocol was further demonstrated by a gram-scale experiment. Mechanistically, dioxygen plays a key role in the cleavage of C-S bonds towards C-N bond formation.

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.

On Water: Metal-Free Synthesis of Highly Functionalized Benzothiazolylidene from ortho-Haloanilines

An environmentally benign, transition-metal-free organic base promoted one-pot cascade synthesis of highly functionalized benzo[ d]thiazol-2(3 H)-ylidene benzamide in the presence of water was accomplished by three-component reaction of ortho-iodoanilines, acrylates, and aroyl isothiocyanates. The protocol involves the in situ generation of thiourea intermediate followed by triethylamine induced intramolecular SN_Ar displacement reaction and subsequent Michael addition onto acrylate leads to the formation of benzo[ d]thiazol-2(3 H)-ylidene benzamide. Benzo[ b]thiazole is also generated in good yields using amidation and intramolecular aromatic nucleophilic substitution chemistry. The control experiments support the proposed mechanistic pathway. Further X-ray crystallographic studies confirmed the assigned structures of the fused benzamide.

Copper-catalyzed synthesis of 2-aminobenzothiazoles from 2-iodophenyl isocyanides, potassium sulfide and amines

A simple and practically useful synthetic method for the synthesis of a variety of 2-aminobenzothiazoles was developed. This methodology could construct one C-N bond and two C-S bonds in a step reaction and provide the desired products in good to perfect yields.

Copper-catalyzed synthesis of 2-aminophenyl benzothiazoles: a novel approach

Substituted 2-aminophenyl benzothiazoles have been constructed from thiourea via copper-catalyzed desulfurization/nucleophilic substitution followed by domino intra- and intermolecular C–N cross-coupling reactions under moderate reaction conditions.

Synthesis and activity mechanism of some novel 2-substituted benzothiazoles as hGSTP1-1 enzyme inhibitors

Human GSTP1-1 is one of the most important proteins, which overexpresses in a large number of human tumours and is involved in the development of resistance to several anticancer drugs. So, it has become an important target in cancer treatment. In this study, 12 benzothiazole derivatives were synthesized and screened for their in vitro inhibitory activity for hGSTP1-1. Among these compounds, two of them (compounds #2 and #5) have been found to be the leads when compared with the reference drug etoposide. In order to analyse the structure-activity relationships (SARs) and to investigate the binding side interactions of the observed lead compounds, a HipHop pharmacophore model was generated and the molecular docking studies were performed by using CDocker method. In conclusion, it is observed that the lead compounds #2 and #5 possessed inhibitory activity on the hGSTP1-1 by binding to the H-site as a substrate in which the para position of the phenyl ring of the benzamide moiety on the benzothiazole ring is important. Substitution at this position with a hydrophobic group that reduces the electron density at the phenyl ring is required for the interaction with the H side active residue Tyr108.

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.

Application of Thio-Ugi Adducts for the Preparation of Benzo[b]thiophene and S-Heterocycle Library via Copper Catalyzed Intramolecular C-S Bond Formation

Fused heterocycles, such as benzo[b]thiophene, thiochroman, benzo[b][1,4]thiazine, and 1,4-benzothiazepine were generated from thio-Ugi adducts containing a thioamide group through copper-catalyzed intramolecular C-S bond formation under microwave irradiation.

Piperazinylpyrimidine modified MCM-41 for the ecofriendly synthesis of benzothiazoles by the simple cleavage of disulfide in the presence of molecular O2

Synthesis of benzothiazoles by metal free cleavage of disulfide bond.

Copper-catalyzed synthesis of 2-aminobenzothiazoles from carbodiimide and sodium hydrosulfide

Copper-catalyzed a coupling/addition tandem reaction for the synthesis of 2-aminobenzothiazoles from o-haloarylcarboniimide and NaHS.

Synthesis of 4-substituted imino-4H-benzo[d][1,3] thiazin-2-amines via palladium-catalysed isocyanide insertion in 2-bromophenylthioureas

The palladium-catalysed isocyanide insertion in 2-bromophenylthioureas leads to the formation of 4-substituted imino-4H-benzo[d][1,3]thiazin-2-amines via C–S cross coupling reaction of the intermediate imidoylpalladium species.

Transition-metal-free direct arylation: synthesis of halogenated 2-amino-2'-hydroxy-1,1'-biaryls and mechanism by DFT calculations

A transition-metal-free, regioselective direct aryl-aryl bond-forming process for the synthesis of halogenated 2-amino-2'-hydroxy-1,1'-biaryls that are currently either inaccessible or challenging to prepare using conventional methods is disclosed. The addition of ArMgX to an o-halonitrobenzene at low temperature generates a transient N,O-biarylhydroxylamine that rapidly undergoes either [3,3]- or [5,5]-sigmatropic rearrangement in one-pot to form a 2-amino-2'-hydroxy-1,1'-biaryl or 1-amino-1'-hydroxy-4,4'-biaryl, respectively. The periselectivity is controlled by the choice of solvent and temperature. This direct arylation process is also readily scalable (1-10 mmol). DFT calculations suggest that from the N,O-biarylhydroxylamine intermediate there is a low-energy stepwise pathway that involves initial Mg-mediated N-O bond cleavage followed by pathway branching toward either [3,3]- or [5,5]-rearrangement products via C-C bond formation and rearomatization.

Novel solid-phase parallel synthesis of N-substituted-2-aminobenzo [d]thiazole derivatives via cyclization reactions of 2-iodophenyl thiourea intermediate resin

A novel solid-phase methodology has been developed for the synthesis of N-alkyl, N-acyl, and N-sulfonyl-2-aminobenzo[d]thiazole derivatives. The key step in this procedure involves the preparation of polymer-bound 2-aminobenzo[d]thiazole resins 5 by cyclization reaction of 2-iodophenyl thiourea resin 3. The resin-bound 2-iodophenyl thiourea 3 is produced by addition of 2-iodophenyl isothiocyanate 2 to the amine-terminated linker amide resin 1. These core skeleton 2-aminobenzo[d]thiazole resins 5 undergo functionalization reactions with various electrophiles, such as alkyl halides, acid chlorides, and sulfonyl chlorides to generate N-alkyl, N-acyl, and N-sulfonyl-2-aminobenzo[d]thiazole resins 6, 7, and 8, respectively. Finally, N-alkyl, N-acyl, and N-sulfonyl-2-aminobenzo[d]thiazole derivatives 9, 10, and 11 are then generated in good yields and purities by cleavage of the respective resins 6, 7, and 8 using trifluoroacetic acid (TFA) in dichloromethane (DCM).

Copper(I) complexes with trispyrazolylmethane ligands: synthesis, characterization, and catalytic activity in cross-coupling reactions

Three novel Cu(I) complexes bearing tris(pyrazolyl)methane ligands, Tpm(x), have been prepared from reactions of equimolar amounts of CuI and the ligands Tpm, (HC(pz)(3)), Tpm*, (HC(3,5-Me(2)-pz)(3)), and Tpm(Ms), (HC(3-Ms-pz)(3)). X-ray diffraction studies have shown that the Tpm and Tpm(Ms) derivatives exhibit a 2:1 Cu:ligand ratio, whereas the Tpm* complex is a mononuclear species in nature. The latter has been employed as a precatalyst in the arylation of amides and aromatic thiols with good activity. The synthesis of a Tpm*Cu(I)-phthalimidate, a feasible intermediate in this catalytic process, has also been performed. Low temperature (1)H NMR studies in CDCl(3) have indicated that this complex exists in solution as a mixture of two, neutral and ionic forms. Conductivity measurements have reinforced this proposal, the ionic form predominating in a very polar solvent such as DMSO. The reaction of Tpm*Cu(I)-phthalimidate with iodobenzene afforded the expected C-N coupling product in 76% yield accounting for its role as an intermediate in this transformation.

Synthesis of 2-mercaptobenzothiazoles via DBU-promoted tandem reaction of o-haloanilines and carbon disulfide

An efficient strategy for the synthesis of a variety of 2-mercaptobenzothiazole derivatives has been developed. The reaction proceeded from o-haloaniline derivatives and carbon disulfide via a tandem reaction in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to afford the corresponding 2-mercaptobenzothiazole derivatives in good to excellent yields.