Molecular Rearrangement of Pyrazino[2,3-c]quinolin-5(6H)-ones during Their Reaction with Isocyanic Acid.

New tetrahydropyrazino[2,3-c]quinolin-5(6H)-ones were prepared from 3-chloroquinoline-2,4(1H,3H)-diones and ethylene diamine. In their reaction with HNCO, an unprecedented molecular rearrangement produced new types of hydantoin derivatives. All prepared compounds were characterized on the basis of their 1H, 13C, and 15N NMR and ESI mass spectra and some were authenticated by X-ray analysis of single crystalline material. A proposed mechanism for rearrangement is discussed in this essay. The CDK and ABL inhibition activity as well as in vitro cytotoxicity of the prepared compounds was also tested.

Reaction of Tertiary 2-Chloroketones with Cyanide Ions: Application to 3-Chloroquinolinediones.

3-Chloroquinoline-2,4-diones react with cyanide ions in dimethyl formamide to give 3-cyanoquinoline-2,4-diones in small yields due to the strong hindrance of the substituent at the C-3 atom. Good yields can be achieved if the substituent at this position is the methyl group. In the methanol solution, the reaction proceeds by an addition mechanism to form 2-oxo-1a,2,3,7b-tetrahydrooxireno[2,3-c]quinoline-7b-carbonitriles, from which 4-hydroxy-3-methoxy-2-oxo-1,2,3,4-tetrahydroquinoline-4-carbonitriles are subsequently formed by opening of the epoxide ring with methanol. Some minor products of these reactions have also been isolated. The 1 H, 13 C and 15 N NMR spectra of the prepared compounds were measured, and all resonances were assigned using appropriate two-dimensional spectra.

New Mono- and Diesters with Imidazoquinolinone Ring- Synthesis, Structure Characterization, and Molecular Modeling.

The objective of the studies was to synthesize and characterize new mono- and diesters with an imidazoquinolin-2-one ring with the use of 2,3-dihydro-2-thioxo-1H-imidazo[4 ,5-c]-quinolin-4(5H)-ones and ethyl bromoacetate. The products were isolated at high yield and characterized by instrumental methods (IR, 1H-, 13C-, and 15N- NMR, MS-ESI, HR-MS, EA). In order to clarify the places of substitution and the structure of the derivatives obtained, molecular modeling of substrates and products was performed. Consideration of the possible tautomeric structures of the substrates confirmed the existence only the most stable keto form. Based on the free energy of monosubstituted ester derivatives, the most stable form were derivatives substituted at sulfur atom of enolic form the used imidazoquinolones. Enolic form referred only to nitrogen atom no 1. The modeling results were consistent with the experimental data. The HOMO electron densities at selected atoms of each substrate has shown that the most reactive atom is sulfur atom. It explained the formation of monoderivatives substituted at sulfur atom. The diester derivatives of the used imidazoquinolones had second substituent at nitrogen atom no. 3. The new diesters can be used as raw material for synthesis of thermally stable polymers, and they can also have biological activity.

Design, synthesis and antitubercular potency of 4-hydroxyquinolin-2(1H)-ones.

In this study, a 50-membered library of substituted 4-hydroxyquinolin-2(1H)-ones and two closely related analogues was designed, scored in-silico for drug likeness and subsequently synthesized. Thirteen derivatives, all sharing a common 3-phenyl substituent showed minimal inhibitory concentrations against Mycobacterium tuberculosis H37Ra below 10 µM and against Mycobacterium bovis AN5A below 15 µM but were inactive against faster growing mycobacterial species. None of these selected derivatives showed significant acute toxicity against MRC-5 cells or early signs of genotoxicity in the Vitotox™ assay at the active concentration range. The structure activity study relation provided some insight in the further favourable substitution pattern at the 4-hydroxyquinolin-2(1H)-one scaffold and finally 6-fluoro-4-hydroxy-3-phenylquinolin-2(1H)-one (38) was selected as the most promising member of the library with a MIC of 3.2 µM and a CC50 against MRC-5 of 67.4 µM.

Synthesis of 1,4-Benzodiazepine-2,5-diones by Base Promoted Ring Expansion of 3-Aminoquinoline-2,4-diones.

An unprecedented reactivity of 3-aminoquinoline-2,4-diones is reported. Under basic conditions, these compounds undergo molecular rearrangement to furnish 1,4-benzodiazepine-2,5-diones. The transformations take place under mild reaction conditions by using 1,1,3,3-tetramethylguanidine, NaOEt, or benzyltrimethylammonium hydroxide as a base. A proposed mechanism of the rearrangement and the conformational equilibrium of 1,4-benzodiazepine-2,5-dione rings are discussed.

New modification of the Perkow reaction: halocarboxylate anions as leaving groups in 3-acyloxyquinoline-2,4(1H,3H)-dione compounds.

Substituted 3-(fluoroacyloxy)quinoline-2,4(1H,3H)-diones including 3-(fluoroiodoacetoxy) derivatives react with triethyl phosphite to afford either the product of the Perkow reaction or the corresponding 4-ethoxyquinolin-2(1H)-one. In both reactions, the fluorocarboxylate anion acts as the first observed leaving group. This observation restricts the application of the intramolecular Horner-Wadsworth-Emmons synthesis to modify quinoline-2,4(1H,3H)-diones by the annulation of fluorinated but-2-enolide rings.

Novel tandem hydration/cyclodehydration of alpha-thiocyanatoketones to 2-oxo-3-thiazolines. Application to thiazolo[5,4-c]quinoline-2,4(3aH,5H)-dione synthesis.

Novel tandem hydration of alpha-thiocyanatoketones to thiocarbamates followed by in situ cyclodehydration to fused 2-oxo-3-thiazolines is described. The reaction is applied to the synthesis of [1,3]thiazolo[5,4-c]quinoline-2,4(3aH,5H)-diones (4). Concentrated sulfuric acid was found to be critical for the reaction as both corresponding 2,3-dioxo-1,2,3,4-tetrahydroquinolin-3-yl thiocyanates (2) and S-(2,4-dioxo-1,2,3,4-tetrahydroquinolin-3-yl) thiocarbamates (3) rapidly hydrolyze in the presence of water to 4-hydroxyquinolin-2(1H)-ones (1).