Synthesis and antimycobacterial activity of pyrazine and quinoxaline derivatives

Coordinated assembly of a new 3D mesoporous Fe3O4@Cu2O–graphene oxide framework as a highly efficient and reusable catalyst for the synthesis of quinoxalines

A novel 3D mesoporous Fe₃O₄@Cu₂O–graphene oxide framework as a highly efficient and reusable catalyst was synthesized.

Palladium catalyzed ortho-halogenation of 2-arylbenzothiazole and 2,3-diarylquinoxaline

A Pd-catalysed mono and di-o-halogenation strategy has been demonstrated selectively using benzothiazoles and quinoxalines as the directing substrates.

I2/Cu-mediated self-sorting domino reaction of aryl β-ketoesters into symmetrical 2-carboalkoxy-1,4-enediones: application to synthesis of pyrazine, β-carboline and quinoxalines

A self-sorting domino reaction of aryl β-ketoesters into symmetrical 1,4-enediones is reported by an I₂/Cu system.

Ugi-based approaches to quinoxaline libraries

An expedient and concise Ugi-based unified approach for the rapid assembly of quinoxaline frameworks has been developed. This convergent and versatile method uses readily available commercial reagents, does not require advanced intermediates, and exhibits excellent bond-forming efficiency, thus exemplifying the operationally simple synthesis of quinoxaline libraries.

l-Proline mediated synthesis of quinoxalines; evaluation of cytotoxic and antimicrobial activity

A simple, greener and highly efficient method for the synthesis of functionalized quinoxalines has been developed employing l-proline as a catalyst in water. The newly synthesized quinoxaline–sulphonamide conjugates exhibited significant cytotoxic and antimicrobial activities.

6a-Nitro-6-(2,2,7,7-tetra-methyl-tetra-hydro-3aH-bis-[1,3]dioxolo[4,5-b:4',5'-d]pyran-5-yl)-6a,6b,7,8,9,11a-hexa-hydro-6H-spiro-[chromeno[3,4-a]pyrrolizine-11,11'-indeno-[1,2-b]quinoxaline]

In the title compound, C39H38N4O8, the quinoxaline and indene subunits are essentially planar, with maximum deviations of 0.071 (2) and 0.009 (2) Å, respectively. The indeno-quinoxaline system forms a dihedral angle of 72.81 (3)° with the chromenopyrrolizine system. The two dioxolane rings, as well as the pyran ring of the chromeno group and the terminal pyrrolizine, each adopt an envelope conformation with O and C as flap atoms. The central pyrrolizine ring adopts a twisted conformation. Intra-molecular C-H⋯O and C-H⋯N hydrogen bonds occur. The crystal structure exhibits C-H⋯O hydrogen bonds, and is further stablized by C-H⋯π inter-actions, forming a two-dimensional network along the bc plane.

Novel syntheses of aryl quinoxaline C-nucleoside analogs by mild and efficient three-component sequential reactions

Novel syntheses of aryl quinoxaline C-nucleoside analogs have been accomplished by mild and efficient three-component sequential reactions in high yields with a wide scope of substrates.

Synthesis and evaluation of a pyrazinoic acid prodrug in Mycobacterium tuberculosis

Tuberculosis (TB) is a disease caused mainly by infection of Mycobacterium tuberculosis affecting more than ten million people around the world. Despite TB can be treated, the rise of MDR-TB and XDR-TB cases put the disease in a worrying status. As pyrazinamide-resistant strains exhibit low or none pyrazinamidase activity, it is proposed that the active form of pyrazinamide (PZA) is pyrazinoic acid (POA), although this acid has poor penetration in mycobacteria. In this work, we present a convenient one-pot synthesis of 2-chloroethyl pyrazinoate, and its activity in M. tuberculosis H37Rv (ATCC27294) in MIC assay using the MABA technique. The obtained MIC of the compound was 3.96 g/mL, and discussion about the activity profile of some previously evaluated pyrazinoates is also performed.

Antimicrobial activity of imidazo[1,5-a]quinoxaline derivatives with pyridinium moiety

3-Phenyl(methyl)-5-alkyl-1-(pyridin-3-yl)imidazo[1,5-a]quinoxalin-4-ones (2a-f) and their N-alkyl-pyridinium salts (3a-o), including 1,n-bis{3-(3-phenylimidazo[1,5-a]quinoxalin-4(5H)-on-1-yl)pyridinium}alkane dibromides (4a-d, 5, 6) have been synthesized. It has been established that the antimicrobial properties of imidazo[1,5-a]quinoxaline derivatives are connected with the presence of various alkyl substituents in the position 1 of the pyridine ring and in the position 5 of the imidazo[1,5-a]quinoxaline system. Chlorides and iodides are more active towards bacteria than fungi. Compounds 3d, 3e, 3m and 3n showed an effective bacteriostatic activity. Compound showed not only well defined bacteriostatic activities but also good fungistatic activities, with the MIC values comparable with the reference drugs. Toxicity of more effective (imidazo[1,5-a]quinoxalin-4-on-1-yl)-1-pyridinium halides was examined in mice.

8,15-Dioxa-10,13-di-aza-tetra-cyclo-[14.4.0.0(2,7).0(9,14)]icosa-1(16),2,4,6,9(14),10,12,17,19-nona-ene

The asymmetric unit of the title compound, C₁₆H₁₀N₂O₂, contains one half-mol­ecule, the complete mol­ecule being generated by twofold rotation symmetry. The plane of the pyrazine ring forms a dihedral angle of 64.87 (6)° with that of the benzene ring, and the planes of the two benzene rings are inclined to one another by 54.20 (6)°. The O atom deviates from the plane of the benzene ring by 0.1549 (8) Å. There are no significant inter­molecular inter­actions in the crystal.

3-[2-(3-Phenyl-2-oxo-1,2-di-hydro-quin-oxalin-1-yl)eth-yl]-1,3-oxazolidin-2-one

The di­hydro­quinoxaline ring system of the title mol­ecule, C₁₉H₁₇N₃O₃, is approximately planar [maximum deviation = 0.050 (2) Å], the dihedral angle between the planes through the two fused rings being 4.75 (8)°. The mean plane through the fused-ring system forms a dihedral angle of 30.72 (5)° with the attached phenyl ring. The mol­ecular conformation is enforced by C—H⋯O hydrogen bonds. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds, forming a three-dimensional network.