Chemical Modification of Plant Alkaloids. 2. Reaction of Cotarnine with Barbituric Acid Derivatives and Structure of 5-Dihydrocotarnylbarbituric Acids

The reaction of barbituric acid and its N-substituted derivatives and 2-thio analogs with cotarnine forms 5-(4-methoxy-6-methyl-5,6,7,8-tetrahydro-2H-1,3-methylenedioxy-[4,5-g]isoquinolinyl-1)barbituric acids, a new class of zwitter-ions, the structure of which was studied by ¹ H and ¹³ C NMR spectroscopy and mass spectrometry. The prepared compounds exist in solution as stable intermolecular associates and have a complicated H-bonded structure.     

Distal γ-C(sp3)−H Olefination of Ketone Derivatives and Free Carboxylic Acids

Reported herein is the distal γ-C(sp³)−H olefination of ketone derivatives and free carboxylic acids. Fine tuning of a previously reported imino-acid directing group and using the ligand combination of a mono-N-protected amino acid (MPAA) and an electron-deficient 2-pyridone were critical for the γ-C(sp³)−H olefination of ketone substrates. In addition, MPAAs enabled the γ-C(sp³)−H olefination of free carboxylic acids to form diverse six-membered lactones. Besides alkyl carboxylic acids, benzylic C(sp³)−H bonds also could be functionalized to form 3,4-dihydroisocoumarin structures in a single step from 2-methyl benzoic acid derivatives. The utility of these protocols was demonstrated in large scale reactions and diversification of the γ-C(sp³)−H olefinated products.     

Facile One-Pot Synthesis of 1,2,3,4-Tetrahydroquinoline-3-carboxylic Acids and Their Heterocyclic Analogs

A facile one-pot method for the synthesis of 1,2,3,4-tetrahydroquinoline-3-carboxylic acids and their heterocyclic analogs based on the tert-amino effect. A set of 1,2,3,4-tetrahydroquinoline-3-carboxylic acids was readily prepared starting from various ortho-dialkylaminoaldehydes and Meldrum's acid using Me₃SiCl in dimethylformamide (DMF) solution.     

Distal γ‐C(sp3)−H Olefination of Ketone Derivatives and Free Carboxylic Acids

Reported herein is the distal γ‐C(sp³)?H olefination of ketone derivatives and free carboxylic acids. Fine tuning of a previously reported imino‐acid directing group and using the ligand combination of a mono‐N‐protected amino acid (MPAA) and an electron‐deficient 2‐pyridone were critical for the γ‐C(sp³)?H olefination of ketone substrates. In addition, MPAAs enabled the γ‐C(sp³)?H olefination of free carboxylic acids to form diverse six‐membered lactones. Besides alkyl carboxylic acids, benzylic C(sp³)?H bonds also could be functionalized to form 3,4‐dihydroisocoumarin structures in a single step from 2‐methyl benzoic acid derivatives. The utility of these protocols was demonstrated in large scale reactions and diversification of the γ‐C(sp³)?H olefinated products.     

Features of synthesis and structure of ethyl (2<Emphasis Type="Italic">Z</Emphasis>)-3-hydroxy-(2,3,4,5-tetrafluorophenyl)-propyl-2-enoate

The structure of key intermediates in the synthesis of fluoroquinolone antibiotics: diethyl (2,3,4,5-tetrafluorobenzoyl)malonate and ethyl (2Z)-3-hydroxy-(2,3,4,5-tetrafluorophenyl)prop-2-enoate was for first time studied using X-ray diffraction (XRD) and ¹H, ¹⁹F NMR spectroscopy. In solution both the esters were shown to exist as a mixture of enol and ketone tautomeric forms with predominance of the latter. According to the XRD analysis, ethyl (2Z)-3-hydroxy-(2,3,4,5-tetrafluorophenyl)prop-2-enoate in the solid state exists entirely in the enol form.     

Chemical modification of plant alkaloids. 5. Spirocyclic systems based on cotarnine and barbituric acids

Cotarnine was reacted with barbituric acid and its N-alkylbartituric and 1,3-dimethyl-2-thio analogs under forcing conditions to produce spirocyclic systems. Adducts, further transformations of which included skeletal rearrangements (a type of T-reaction) and subsequent deamination, were formed in the first step. The reaction of N-methylcotarnine and 1,3-dimethylbarbituric acid was analogous. The properties of the spirocyclic products were studied. They were further modified at the CH-acid and aromatic moieties. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 38–42, January–February, 2008.     

Synthesis and structure of new 3-pyrazolinylcoumarins and 3-pyrazolinyl-2-quinolones

The reactions of substituted 3-cinnamoyl-4-hydroxycoumarins and 3-cinnamoyl-4-hydroxy-2-quinolones with different phenylhydrazines gave 3-hetaryl-1H-4,5-dihydropyrazoles. The product structures were studied by ¹H NMR spectroscopy and mass spectrometry. 4-Hydroxy-3-pyrazo-linylcoumarins exist in DMSO as two tautomers (4-enol and chromane-2,4-dione), while 4-hydroxy-3-pyrazolinyl-2-quinolones exist only in the enol form. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1479–1486, July, 2008.     

Synthesis,Structure, and Keto-Enol Tautomerism of 3-R<Superscript>1</Superscript>-5,5-R<Superscript>2</Superscript>,R<Superscript>2</Superscript>-6-R<Superscript>3</Superscript>-2,3,5,6-Tetrahydropyran-2,4-diones

Ethyl esters of 2,4-dibromo-2-R¹-4-R²-3-oxopentanoic and -hexanoic acids react with zinc and aliphatic or aromatic aldehydes under the conditions of the Reformatskii reaction to give 3-R¹-5,5-R², R²-6-R³-2,3,5,6-tetrahydropyran-2,4-diones, which are obtained in three forms: keto, enol with enolization of the keto group, and enol with enolization of the ester group. The keto form is isolated by crystallization from a mixture of CCl₄ and petroleum ether; the first enol form, from MeOH, EtOH, and polar aprotic solvents; and the second enol form, from CHCl₃. The second enol form is oxidized in DMSO to form a keto compound containing a hydroxy group at the 3-position of the heteroring.     

Spectrophotometric Studies on Some Arylazo Barbituric Acids and Arylazo Pyrimidine in Organic Solvents and in Buffer Solutions

The UV and visible spectra of some arylazo barbituric acids and arylazo pyrimidine in pure and mixed organic solvents of varying polarities have been studied. The different absorption bands displayed in the electronic spectra of these compounds are assigned and the possibility of the existence of these compounds in tautomeric equilibrium as well as in intra‐ and intermolecular H‐bonding were examined. The solute‐solvents molecular complexes liable to exist in polar‐nonpolar mixed solvents are investigated. The structure of the azo compounds were confirmed by ¹H NMR and IR spectroscopy. The ionization processes of the compounds were investigated and the possible ionization constants were determined and discussed in terms of molecular structure of the azo compounds.     

Synthesis,Spectroscopic Studies and Keto-Enol Tautomerism of Novel 1,3,4-Thiadiazole Derivative Containing 3-Mercaptobutan-2-one and Quinazolin-4-one Moieties

In this study, a novel 1,3,4-thiadiazole derivative containing 3-mercaptobutan-2-one and quinazolin-4-one moieties (Compound 3) is synthesized by the coupling of 2-amino-1,3,4-thiadiazole-5-(3-mercaptobutan-2-one) (Compound 1) with 2-Phenyl-4H-3,1-benzoxazin-4-one (Compound 2) in one molecule moiety. Compound 3 is found to exist as two types of intra-molecular hydrogen bonding with keto-enol tautomerism characters, which is further confirmed using FTIR, ¹H-NMR, ¹³C-NMR, mass spectrometer, and UV-Visible spectra. The ¹H-NMR and UV-Visible spectra of Compound 3 are investigated in different solvents such as methanol, chloroform, and DMSO. Compound 3 exhibits keto-enol tautomeric forms in solvents with different percentage ratios depending on the solvent polarity. The ¹H-NMR and UV-Visible spectral results show that Compound 3 favors the keto over the enol form in polar aprotic solvents such as DMSO and the enol over the keto form in non-polar solvents such as chloroform. The ¹³C-NMR spectrum gives two singles at δ 204.5 ppm, due to ketonic carbon, and δ 155.5 ppm, due to enolic carbon, confirming the keto-enol tautomerism of Compound 3. Furthermore, the molecular ion at m/z 43 and m/z 407 in the mass spectrum of Compound 3 and fragmentation mechanisms proposed reveal the existence of the keto and enol forms, respectively.     

1, 5-Rearrangement of enol acylates of aryl 1H.-1, 2, 4-triazol-1-ylmethyl ketones

The rearrangement of enol acylates of aryl 1H-1, 2, 4-triazol-1-ylmethyl ketones at 140–150°C in acetic anhydride is studied. The migration of the acyl group to the C(5) atom of the heterocycle is found to be intramolecular. The characteristics of the original and final products are presented. X-ray structural studies of the enol acetates of 2, 4-dichlorophenyl 1H-1, 2, 4-triazol-1-ylmethyl ketone and 2, 4-dichlorophenyl 5-acetyl-1H-1, 2, 4-triazol-1-ylmethyl ketone are carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 560–564, March, 1993.     

Reaction of 1-Aryl-3-methylpyrazol-5-ones with 2-Cyanoaryldiazonium Bisulfates

2-Cyanoaryldiazonium bisulfates, obtained by the action of nitrosyl sulfuric acid on isatin 3-hydrazone and its 5-bromo and 5-nitro derivatives, couple with 1-aryl-3-methylpyrazol-5-ones and form 4-arylhydrazones of 1-aryl-3-methylpyrazole-4,5-diones. It was established on the basis of data of IR, UV, and ¹H NMR spectra and of X-ray structural analysis that the coupling products exist in the hydrazone form stabilized by an intramolecular hydrogen bond.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 210–215, February, 2005.     

Keto-Enol Tautomeric Equilibrium in 4-Oxo-1,1,3-Cyclohexanetricarboxylic Acid Trialkyl Esters and 4-Oxo-1, 1, 3-Cyclopentanetricarboxylic Acid Trialkyl Esters

4-Oxo-1,1,3-cyclohexanetricarboxylic acid trialkyl esters in deuterochloroform and dimethylsulfoxide-d⁶ (DMSO) exist exclusivly in the enol form. The keto form is the major component in the analogous compounds of five-membered ring. The 1, 3 interaction between carboalkoxy groups in the six-membered ring should be the reason why the carboalkoxy group at 3-position is in equatorial configuration and engages in the intramolecular hydrogen bond, so that the enol form is dominating.     

4-Hydroxy-2-quinolones 171*. Synthesis,isomerism, and antitubercular activity of 1-R-4-hydroxy-2-oxo-1,2-dihydro-quinoline-3-carboxylic acid alkylidenehydrazides

Alkylidenehydrazides have been synthesized by the reaction of 1-R-4-hydroxy-2-oxo-1,2-dihydro-quinoline-3-carboxylic acid hydrazides with lower dialkyl ketones in order to reveal a structure-antitubercular activity relationship. It was shown by ¹H NMR spectroscopy that hydrazones obtained from the unsymmetrical ketone – methyl ethyl ketone – exist primarily in the E-isomer form. It was found that the presence of two aliphatic substituents in the alkylidene fragment of the compounds investigated leads to a marked lowering of antimicobacterial properties.     

Ultraviolet spectra of 2-phenyl-4- and 2-phenyl-5-azaindan-1, 3-diones

The UV spectra of 2-phenyl-4-azaindan-1, 3-dione (I), 2-phenyl-5-azaindan-1, 3-dione (II), and their N-methylbetaines are investigated. 2×10^–5 M aqueous alcoholic solutions of 2-phenyl-4-azaindan-1, 3-dione (I) contain the anionic form (IA), and in solutions of 2-phenyl-5-azaindan-1, 3-dione (II) the betaine form (IIB) is also in equilibrium with the anion (IIA). Solutions of I and II in 0.1 M sulfuric acid are characterized by a wide and rather intense absorption band at about 500 m, indicating the presence of a betaine form (IB and IIB). In 2M hydrochloric acid solution 2-phenylazaindan-1, 3-diones and their N-methylbetaines (III and IV) are protonated at the oxygen atom, giving the enol forms of the N-protonated or corresponding N-methylated 2-phenylazaindandiones.     

5-(色酮基-3-次甲基)(硫代)巴比妥酸的合成

将巴比妥酸或硫代巴比妥酸、3-甲酰基色酮在乙酸-乙酸酐溶液(含乙酸酐10%)中进行缩合反应,制备了5-(色酮基-3-次甲基)(硫代)巴比妥酸.并经元素分析,IR,1H NMR及13C NMR确证了产物的结构.     

4-Methyl morpholinium bis-(thio)barbiturates: Synthesis,structure, anticancer evaluation,and CoMFA study

The reaction of symmetrical (thio)barbituric acids with aldehydes in the presence of 4-methyl morpholine yielded a new form of 4-methyl morpholinium bis-(thio)barbiturate containing charge-separated intermolecular and eight-membered intramolecular H-bonds. X-ray Crystallography, FT-IR, and ¹H and ¹³C-NMR spectroscopy techniques were used for structure characterizations. Some of these compounds showed potent anticancer activities. Cytotoxicity of the synthetic compounds against HeLa and MCF-7 cell lines were performed by MTT assay. In addition, a comparative molecular field analysis was carried out, and the effects of substituents on the biological activities of these compounds were explained.     

Cationic ruthenium complex of the formula [RuCl(2,6-diacetylpyridine)(PPh3)2]BArF and its catalytic activity in the formation of enol esters

A new ruthenium 2,6-diacetylpyridine complex was synthesized and applied in the atom-economic synthesis of enol esters through Markovnikov-directed addition of carboxylic acids to terminal alkynes. The ruthenium complex [RuCl(dap)(PPh₃)₂]⁺BArF^? was synthesized from [RuCl₂(PPh₃)₂] and the corresponding ligand 2,6-diacetylpyridine (dap). The complex was characterized structurally. The new ruthenium complex was utilized under ambient conditions as a catalyst in the Markovnikov addition of carboxylic acids to terminal alkynes to afford the corresponding enol esters in 93% to 52% isolated yields (85?°C, 16?h reaction time, 1?mol% catalyst loading).     

Interaction of Hydroxylamine with Esters of 2-Oxobutenoic Acids. Synthesis of 1-Hydroxy-3-hydroximino-2-pyrrolidinones

New 3-hydroximino-1-hydroxy-2-pyrrolidinones have been synthesized by the interaction of NH₂OH and NH₂OBn with the methyl esters of 2-oxo-3-butenoic acid derivatives. Some intermediate compounds have been isolated and identified and the reaction mechanism is discussed.     

Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds

Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1).