Thiazolo[3,2-a]benzimidazoles: synthetic strategies, chemical transformations and biological activities

Design and synthesis of benzothiazole-based SLC-0111 analogues as new inhibitors for the cancer-associated carbonic anhydrase isoforms IX and XII

In this work, different series of benzothiazole-based sulphonamides 8a-c, 10, 12, 16a-b and carboxylic acids 14a-c were developed as novel SLC-0111 analogues with the goal of generating potent carbonic anhydrase (CA) inhibitors. The adopted strategy involved replacing the 4-fluorophenyl tail in SLC-0111 with a benzothiazole motif that attached to the ureido linker to produce compounds 8c and its regioisomers 8a-b. In addition, the ureido spacer was elongated by methylene or ethylene groups to afford the counterparts 10 and 12. In turn, the primary sulfamoyl zinc binding group (ZBG) was either substituted or replaced by carboxylic acid functionality in order to provide the secondary sulphonamide-based SLC-0111 analogues 16a-b, and the carboxylic acid derivatives 14a-c, respectively. All compounds (8a-c, 10, 12, 14a-c and 16a-b) were tested for their ability to inhibit CA isoforms CA I, II, IX and XII. Additionally, the in vitro anticancer properties of the developed CAIs were evaluated.

Visible light-promoted intermolecular cyclization/aromatization of chalcones and 2-mercaptobenzimidazoles via an EDA complex and a mechanism study

Visible-light-promoted cyclization and aromatization of chalcones with 2-mercaptobenzimidazoles have been successfully developed to obtain diverse imidazo[2,1-b]thiazoles, and C-S and C-N bonds were constructed in one step. The reaction uses oxygen in the air as an oxidant, and the method does not need an external photocatalyst or a transition metal catalyst. The strategy features mild conditions, a simple system, readily accessible feedstocks, and a friendly environment. UV absorption spectroscopy and control experiments have shown that the reaction mechanism involves the formation of an electron-donor-acceptor (EDA) complex from thiolate anions and chalcones. In order to verify the mechanism, we studied the structure and HOMO/LUMO of the EDA complex by density functional theory (DFT) calculations. The results show that the π-π stacking between chalcones and 2-mercaptobenzimidazoles will cause a red shift of the UV absorption wavelength in the presence of Cs₂CO₃, and also provide a theoretical basis for the electron transfer of EDA complexes.

Selective Thiocyanation and Aromatic Amination To Achieve Organized Annulation of Enaminone with Thiocyanate

A tandem insertion of thiocyanate to enamine was performed for the regioselective synthesis of multisubstituted benzoimidazo[2,1-b]thiazoles. This method was shown to be effective in addressing the issue of isomerization encountered in common strategies. With a change made to the leading group on the aniline fragment of enamine, the reaction achieved different transformations, thus enabling multisubstituted benzo[4,5]imidazo[2,1-b]thiazoles and thiazoles in satisfactory yields.

The Potential of Peroxidases Extracted from the Spent Mushroom (Flammulina velutipes) Substrate Significantly Degrade Mycotoxin Deoxynivalenol

Little is known about the degradability of mycotoxin deoxynivalenol (DON) by the spent mushroom substrate (SMS)-derived manganese peroxidase (MnP) and lignin peroxidase (LiP) and its potential. The present study investigated the growth inhibition of Fusarium graminearum KR1 and the degradation of DON by MnP and LiP extracted from SMS. The results from the 7-day treatment period showed that mycelium inhibition of F. graminearum KR1 by MnP and LiP were 23.7% and 74.7%, respectively. Deoxynivalenol production in the mycelium of F. graminearum KR1 was undetectable after treatment with 50 U/mL of MnP or LiP for 7 days. N-acetyl-D-glucosamine (GlcNAc) content and chitinase activity both increased in the hyphae of F. graminearum KR1 after treatment with MnP and LiP for 1, 3, and 6 h, respectively. At 12 h, only the LiP-treated group had higher chitinase activity and GlcNAc content than those of the control group (p < 0.05). However, more than 60% of DON degradabilities (0.5 mg/kg, 1 h) were observed under various pH values (2.5, 4.5, and 6.5) in both MnP (50 U/g) and LiP (50 U/g) groups, while DON degradability at 1 mg/kg was 85.5% after 50 U/g of LiP treatment for 7 h in simulated pig gastrointestinal tracts. Similarly, DON degradability at 5 mg/kg was 67.1% after LiP treatment for 4.5 h in simulated poultry gastrointestinal tracts. The present study demonstrated that SMS-extracted peroxidases, particularly LiP, could effectively degrade DON and inhibit the mycelium growth of F. graminearum KR1.

Mol-ecular and crystal structure, Hirshfeld analysis and DFT investigation of 5-(furan-2-yl-methyl-idene)thia-zolo[3,4-a]benzimidazole-2-thione

The thia-zolo[3,4-a]benzimidazole fused-ring system in the title compound, C14H8N2OS2, is nearly planar, the r.m.s. deviation being 0.0073 Å. The thia-zolo-benzimidazole-2-thione system is almost in the same plane as the furan-2-yl-methyl-ene moiety, with a dihedral angle of 5.6 (2)° between the two least-squares planes. In the crystal, adjacent mol-ecules are connected by weak inter-molecular inter-actions (C-H⋯N and slipped π-π stacking) into a three-dimensional network. The nature of the inter-molecular inter-actions was also qu-anti-fied by Hirshfeld surface analysis. DFT analysis indicates a good agreement of the experimentally determined and the theoretically calculated mol-ecular structures.

Fused azole-thiazolines via one-pot cyclization of functionalized N-heterocyclic carbene precursors

Various bi/tricyclic azole-thiazolines are obtained via a new one-pot protocol from cheap starting materials.

Copper-catalyzed aminothiolation of terminal alkynes with tunable regioselectivity

A simple, mild, and efficient catalytic aminothiolation of terminal alkynes for the synthesis of both 2- and 3-substituted thiazolo[3,2-a]benzimidazoles is established upon catalysis with copper(i), in which complementary regioselectivities could be achieved by using sterically different phenanthroline-based ligands.

The synthesis of benzimidazoles via a recycled palladium catalysed hydrogen transfer under mild conditions

An efficient synthesis of benzimidazoles was developed by virtue of a recycled palladium catalyzed hydrogen transfer.

A review on bis-hydrazonoyl halides: Recent advances in their synthesis and their diverse synthetic applications leading to bis-heterocycles of biological interest

This review covers a summary of the literature data published on the chemistry of bis-hydrazonoyl halides over the last four decades. The biological activities of some of the bis-heterocyclic compounds obtained from these bis-hydrazonoyl halides are also reviewed and discussed.

Synthesis of novel thiazole-based 8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines as potential antitumor and antifungal agents

A new series of novel thiazole-based 8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines 6a-g and 7a-g were obtained with high regioselectivity from the reaction of triamino- or tetraaminopyrimidines 4 and 5 with α,β-unsaturated carbonyl compounds 3a-g based on 2,4-dichlorothiazol-5-carbaldehyde 1. Twelve of the synthesized compounds were selected and tested by US National Cancer Institute (NCI) for their antitumor activity against 60 different human tumor cell lines. Compounds 7d and 7g showed important GI50 ranges of 1.28-2.98 μM and 0.35-2.78 μM respectively under in vitro assays. In addition, 6a-g and 7a-g were tested for antifungal properties against the clinical important fungi Candida albicans and Cryptococcus neoformans. Although these compounds showed moderate activities against C. albicans, the 2-amino derivatives 7a-g and mainly 7a and 7b, showed high activity against standardized and clinical isolates of C. neoformans with MIC50 = 7.8-31.2 μg/mL, MIC80 = 15.6-31.2 μg/mL and MIC100 = 15.6-62.5 μg/mL. In addition, since both compounds were fungicide rather than fungistatic these thiazole-based 8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines appear as good candidates for further development not only as antifungal but also as antitumor drugs.

Synthesis of 2-arylbenzimidazoles under mild conditions catalyzed by a heteropolyacid-containing task-specific ionic liquid and catalyst investigation by electrospray (tandem) mass spectrometry

A task-specific ionic liquid constituted by a Bronsted acid (1-(3-sulfopropyl)-3-methyl-imidazolium hydrogen sulfate), namely MSI, and by [PW₁₂O₄₀]³⁻, namely PW, was used for the condensation reaction in the synthesis of 2-arylbenzimidazoles.

(Z)-2-Benzyl-idenebenzo[d]thia-zolo[3,2-a]imidazol-3(2H)-one

The mol-ecule of the title compound, C(16)H(10)N(2)OS, is approximately planar, the dihedral angle between the 1,3-benzothia-zolo[3,2-a]imidazol-3(2H)-one and the benzyl-idene moieties being 4.10 (8)°. A weak intra-molecular C-H⋯S inter-action generates an S(6) ring. No inter-molecular hydrogen bonds are observed in the crystal structure.

3-(3-Methoxyphenyl)benzo[d]thiazolo[3,2-a]imidazol-9-ium hydrogen sulfate

In the title mol­ecular salt, C₁₆H₁₃N₂OS⁺·HSO₄⁻, the thia­zolo[3,2-a]benzimidazolium ring system is roughly planar [maximum deviation = 0.046 (3) Å] and makes a dihedral angle of 58.22 (11)° with the benzene ring. The meth­oxy group is almost coplanar with its attached benzene ring [C_meth­yl—O—C—C = −1.6 (5)°]. In the crystal, the cation is linked to the anion by a bifurcated N—H⋯(O,O) hydrogen bond, generating an R₁²(4) ring motif. The ion pairs are then connected by a C—H⋯O hydrogen bond into inversion dimers and these dimers are further linked by O—H⋯O hydrogen bonds into an infinite tape along [100]. A π–π stacking inter­action [centroid-to-centroid distance = 3.5738 (18) Å] and a short inter­molecular contact [S⋯O = 2.830 (3) Å] are also observed.

(Z)-2-(4-Chloro-benzyl-idene)benzo[d]thia-zolo[3,2-a]imidazol-3(2H)-one

The mol-ecule of the title compound, C(16)H(9)ClN(2)OS, is approximately planar, the dihedral angle between the thia-zolo[3,2-a]benzimidazole ring system and the 4-chloro-phenyl ring being 2.10 (5)°. An intra-molecular C-H⋯S inter-action generates an S(6) ring motif. In the crystal, mol-ecules are stacked into columns along the b axis by π-π inter-actions with centroid-centroid distances of 3.6495 (7)-3.9546 (8) Å.

(Z)-Ethyl 2-(2,4-dimethyl-benzyl-idene)-7-methyl-3-oxo-5-phenyl-3,5-dihydro-2H-thia-zolo[3,2-a]pyrimidine-6-carboxyl-ate

In the title compound, C₂₅H₂₄N₂O₃S, the dihedral angles between the thia­zole ring and the phenyl and substituted benzene rings are 84.91 (11) and 11.58 (10)°, respectively. The dihydro­pyrimidine ring adopts a flattened boat conformation. The olefinic double bond is in a Z configuration.

Ethyl (Z)-2-(2-fluoro-benzyl-idene)-7-methyl-3-oxo-5-phenyl-3,5-dihydro-2H-thia-zolo[3,2-a]pyrimidine-6-carboxyl-ate

The title compound, C₂₃H₁₉FN₂O₃S, a fused-pyrimidine derivative, displays dihedral angles between the thia­zole ring and the benzene ring and substituted benzene ring of 7.10 (14) and 3.48 (12)°, respectively. The dihydro­pyrimidine ring adopts a flattened boat conformation. The olefinic double bond is in a Z configuration.

2-(1H-1,3-Benzodiazol-2-ylsulfanyl)-1-(4-chlorophenyl)ethanone

The mol­ecule in the structure of the title compound, C₁₅H₁₁ClN₂OS, displays two planar residues [r.m.s. deviation = 0.014 Å for the benzimidazole residue, and the ketone group is co-planar with the benzene ring to which it is attached forming a O—C—C—C torsion angle of −173.18 (14) °] linked at the S atom. The overall shape is based on a twisted V, the dihedral angle formed between the two planes being 82.4 (2) °. The amine-H atom is bifurcated, forming N—H⋯O and N—H⋯S hydrogen bonds leading to dimeric aggregates. These are linked into a supra­molecular chain along the c axis via C—H⋯π hydrogen bonds. Chains form layers in the ab plane being connected along the c axis via weak π–π inter­actions [3.9578 (8) Å] formed between centrosymmetrically related chloro-substituted benzene rings.