Convergent Assembly of 1,4-Benzothiazide Spiroindolinones via [4 + 2] Spiroannulation Under Open-Air Conditions

This report discloses a transition-metal-free [4 + 2] spirocyclization of isatin-derived β-silylcarbinols and 2-aminobenzenethiols, providing a facile approach to 1,4-benzothiazide spiroindolinones in decent yields. Control experiments indicate that 3-methylene oxindoles and disulfides are key intermediates in this tandem reaction. Moreover, the resulting products can be facilely converted into pharmaceutically significant sulfone and sulfoxide scaffolds, which further demonstrates the potential utility of this protocol.

Synthesis and crystal structures of two racemic 2-heteroaryl-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-ones

3-Phenyl-2-(thio-phen-3-yl)-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one (C17H12N2OS2, 1) and 2-(1H-indol-3-yl)-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one 0.438-hydrate (C21H15N3OS·0.438H2O, 2) crystallize in space groups P21/n and C2/c, respectively. The asymmetric unit in each case is comprised of two parent mol-ecules, albeit of mixed chirality in the case of 1 and of similar chirality in 2 with the enanti-omers occupying the neighboring asymmetric units. Structure 2 also has water mol-ecules (partial occupancies) that form continuous channels along the b -axis direction. The thia-zine rings in both structures exhibit an envelope conformation. Inter-molecular inter-actions in 1 are defined only by C-H⋯O and C-H⋯N hydrogen bonds between crystallographically independent mol-ecules. In 2, hydrogen bonds of the type N-H⋯O between independent mol-ecules and C-H⋯N(π) type, and π-π stacking inter-actions between the pyridine rings of symmetry-related mol-ecules are observed.

Novel 1,2-thiazine-pyridine hybrid: Design, synthesis, antioxidant activity and molecular docking study

Background & objectives:

1,2-thiazine and pyridine heterocycles drew much attention due to their biological activities including antioxidant activity. Based upon fragment based drug design, novel pyrido[1,2]thiazines 9a-c, thiazolidinopyrido[1,2]thiazines 10a-c and azetidinopyrido[1,2]thiazines 11a-c were designed and prepared.

Methods:

These novel derivatives 9a-c, 10a-c and 11a-c were subjected to screening for their antioxidant activity via various assays as DPPH radical scavenging potential, reducing power assay and metal chelating potential.

Results:

All the assayed derivatives exhibited excellent antioxidant potential and the tested compounds 9a, 9b, 10a, 10b, 11a and 11b exhibited higher DPPH scavenging potential (EC50 = 32.7, 53, 36.1, 60, 40.6 and 67 µM, respectively) than ascorbic acid (EC50 = 86.58 µM). While targets 9a, 10a and 11a (RP50 = 52.19, 59.16 and 52.25 µM, respectively) exhibited better reducing power than the ascorbic acid (RP50 = 84.66 µM). Computational analysis had been utilized to prophesy the bioactivity and molecular properties of the target compounds.

Conclusion:

To predict the binding manner of the novel derivatives as antioxidants, in-silico docking study had been performed to all the newly prepared compounds inside superoxide dismutase (SOD) and catalase (CAT) active site. The most active antioxidant candidate 9a (EC50 = 32.7 µM, RP50 = 52.19 µM) displayed excellent binding with Lys134 amino acid residing at Cu-Zn loop of SOD with binding energy score = -7.54 Kcal/mol thereby increase SOD activity and decrease reactive oxygen species.

T3P-Promoted Synthesis of a Series of 2-Aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones and Their Activity against the Kinetoplastid Parasite Trypanosoma brucei

A series of fourteen 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-phenyl-C-aryl imines with thionicotinic acid, two difficult substrates. The reactions were operationally simple, did not require specialized equipment or anhydrous solvents, could be performed as either two or three component reactions, and gave moderate–good yields as high as 63%. This provides ready access to N-phenyl compounds in this family, which have been generally difficult to prepare. As part of the study, the first crystal structure of neutral thionicotinic acid is also reported, and showed the molecule to be in the form of the thione tautomer. Additionally, the synthesized compounds were tested against T. brucei, the causative agent of Human African Sleeping Sickness. Screening at 50 µM concentration showed that five of the compounds strongly inhibited growth and killed parasites.

Crystal structures of two solvated 2-aryl-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-ones

The synthesis and crystal structures of 2-(4-fluoro-phen-yl)-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one toluene hemisolvate (1), C19H13FN2OS·0.5C7H8, and 2-(4-nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one iso-propanol 0.25-solvate 0.0625-hydrate (2), C19H13N3O3S·0.25C3H7O·0.0625H2O, are reported. Both are racemic mixtures (centrosymmetric crystal structures) of the individual com-pounds and incorporate solvent mol-ecules in their structures. Compound 2 has four thia-zine mol-ecules in the asymmetric unit. All the thia-zine rings in this study show an envelope pucker, with the C atom bearing the substituted phenyl ring displaced from the other atoms. The phenyl and aryl rings in each of the mol-ecules are roughly orthogonal to each other, with dihedral angles of about 75°. The extended structures of 1 and 2 are consolidated by C-H⋯O and C-H⋯N(π), as well as T-type (C-H⋯π) inter-actions. Parallel aromatic ring inter-actions (π-π stacking) are observed only in 2.

rac-2,3-Diphenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-one 1-oxide

In the title compound, C19H14N2O2S, the thiazine ring exhibits a screw-boat pucker. The oxygen atom on the sulfur atom of the ring is pseudo-axial on the thiazine ring. In the crystal, 21screw-related molecules are linked by C—H...Ocarbonylhydrogen bonds, forming helices propagating along theb-axis direction.

5-Hydroxy-7-azaindolin-2-one, a novel hybrid of pyridinol and sunitinib: design, synthesis and cytotoxicity against cancer cells

Synthesis of a series of hybrid compounds of pyridinol and sunitinib and their cytotoxicity against human cancer cell lines and improved safety windows are described.

1,1′-Sulfinyldipyridinium bis (hydrogen sulfate) ionic liquid: synthesis and application in the temperature-influenced synthesis of novel pyranopyrimidinediones and pyranopyrimidinetriones

A novel and robust dication Brønsted acidic ionic liquid as a catalyst for the temperature influenced synthesis of novel pyranopyrimidinediones and pyranopyrimidinetriones.

Synthesis of novel dispiropyrrolothiazoles by three-component 1,3-dipolar cycloaddition and evaluation of their antimycobacterial activity

A series of dispiropyrrolothiazoles derivatives has been synthesized screenedin vitroagainstMycobacterium tuberculosisH37Rv. The observed regio- and stereoselectivity of the cycloaddition reaction has been rationalized by DFT calculations.