Synthetic Access to New Pyridone Derivatives through the Alkylation Reactions of Hydroxypyridines with Epoxides

General methods for the preparation of a variety of pyridone and oxypyridine derivatives are described. 2‐,3‐,4‐Hydroxy pyridine and 2‐pyridinemethanol were alkylated with ethylene‐, propylene‐, and stryrene‐oxide and epichlorohydrin in the presence of different Lewis acids as a catalyst. The best yield of 3a was achieved in the presence of CdI₂/BF₃ · OEt₂. The corresponding pyridone derivatives (3a–d, 7a–d) were obtained from the reaction of 2‐and 4‐hydroxypyridine with oxiranes in good yields, whereas oxypyridine derivatives (5a–d, 9a,b) were obtained from reactions of 3‐hydroxypyridine and 2‐pyridinemethanol with oxiranes. Chlorohydrines (3d, 5d, 7d) were easily converted to corresponding epoxy derivatives (10, 11, 12) in basic medium; then amino alcohols (13–17) were obtained from the reaction of these epoxy derivatives with amines.     

Nanocomposites of Tantalum‐Based Pyrochlore and Indium Hydroxide Showing High and Stable Photocatalytic Activities for Overall Water Splitting and Carbon Dioxide Reduction

Nanocomposites of tantalum‐based pyrochlore nanoparticles and indium hydroxide were prepared by a hydrothermal process for UV‐driven photocatalytic reactions including overall water splitting, hydrogen production from photoreforming of methanol, and CO₂ reduction with water to produce CO. The best catalyst was more than 20 times more active than sodium tantalate in overall water splitting and 3 times more active than Degussa P25 TiO₂ in CO₂ reduction. Moreover, the catalyst was very stable while generating stoichiometric products of H₂ (or CO) and O₂ throughout long‐term photocatalytic reactions. After the removal of In(OH)₃, the pyrochlore nanoparticles remained highly active for H₂ production from pure water and aqueous methanol solution. Both experimental studies and density functional theory calculations suggest that the pyrochlore nanoparticles catalyzed the water reduction to produce H₂, whereas In(OH)₃ was the major active component for water oxidation to produce O₂.     

Interactions of water and methanol with a mixture of copper and zinc metals: a theoretical <Emphasis Type="Italic">ab initio</Emphasis> study

Ab initio cluster quantum chemical calculations at the Hartree–Fock and second-order Møller–Plesset perturbation theory levels were carried out to mimic the interactions of water and methanol with a mixture of Cu and Zn metals. It was shown that both molecular and dissociative adsorption of methanol on a mixture of Cu and Zn metal catalyst are preferred over the corresponding adsorptions of water. Estimated transition-state structures for dissociation of methanol into CH·₃ and OH· lie about 9.0 and 22.0 kcal/mol higher compared to the dissociated (forward reaction) and molecular adsorption (reverse reaction) complexes, respectively. Based on distinct radicals' bond energies with the active sites of the catalyst considered, it is suggested that hydrogen molecules could be formed through a chain of homogeneous reactions of methyl radicals released into the gas phase with the water and/or methanol molecules.     

Synthesis of 1,4-dioxene from diethylene glycol in the presence of bifunctional copper-containing catalysts. Effect of support on the selectivity of dioxene formation

In the synthesis of 1,4-dioxene from diethylene glycol in the presence of a bifunctional copper-containing catalyst, the composition of the byproducts has been studied and the effect of the support on the overall direction of the reactions has been investigated. It has been established that on Cu/SiO ₂,1,4-dioxanone is formed together with dioxene, the yield of the former increasing with an increase in the content of copper in the catalyst. This is due to an increase in the dehydrogenating function of the latter. On the more acidic Cu/Al ₂O₃,1, 4-dioxane is mainly obtained together with, to a lesser degree, methyl-1, 3-dioxolane. This is due to the predominance of dehydration reactions followed by isomerization. Dioxene, dioxane, and methyldioxolane are formed on Cu/HNaY, and the yield of the latter increases with an increase in the degree of acidity (degree of decationization) of the zeolite. It is possible to increase the selectivity of dioxene formation substantially with the use of a catalyst with a moderately acidic zeolite, by varying its copper content and by dilution with water vapor.     

BIS-DESULFOGLUCOSINOLATES: A NEW CLASS OF BOLAFORMS

ABSTRACT

Bis-desulfoglucosinolates 14–18 bearing d-gluco, lacto, malto and cellobio saccharidic moieties were synthesized in two steps from the corresponding protected 1-thio-β-d-glycopyranoses 5, 8, 10 and 12 and bis-hydroximoyl chlorides 3a and 4a derived from 1,8-octanedial (1) and 1,12-dodecanedial (2). Fully deprotections of the intermediate O-acetylated derivatives 6, 7, 9, 11 and 13 were realized either using Zemplén method or methanol/triethylamine/water mixture, the choice of the conditions being dependent on the solubility in methanol of the fully and partially acetylated derivatives.     

CHOLESTERYL PHOSPHITE AND RELATED COMPOUNDS

Abstract

The preparation of cholesteryl phosphorodichloridite (2) is described; this compound with aniline (2 mol. equiv.) gave the N-phenylphosphoramidochloridite (5) and the latter by condensation with water afforded the N-phenyl-amidophosphite (6).

Similarly the N-phenylphosphoramidochloridite (5) with morpholine gave the morpholidite (7); phenylhydrazine gave the hydrazinophosphite (8) and ethanol the amidoethyl phosphite (9). Cholesteryl phosphorodichloridite (2) by reaction with aniline (4 mol. equiv.) gave the N,N ¹?diphenylphosphorodiamidite (10).

The reaction of cholesteryl phosphorodichloridite (2) with methanol and ethanol are discussed in relation to the analogous reactions with cholesteryl phosphorodichloridate. Boiling ethanol gave cholesterol as the only isolatable product but at room temperature a low yield of the diethylphosphite (11; R=Et) was obtained. The yield of the phosphite was greatly increased in the presence of base. Similarly the dichloridite 2 with boiling water gave cholesterol (1), but at room temperature cholesteryl phosphite 3 was isolated: the mechanistic basis for these different results is briefly discussed.

trans-4-t-Butylcyclohexanol with phosphorus trichloride gave the phosphorodichloridite, which was characterised by conversion to the corresponding N,N ¹?diphenylphosphorodiamidite.     

Highly efficient desilylation of 3-trimethylsilylprop-2-ynamides by the action of KF-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A highly effective procedure has been developed for desilylation of 3-trimethylsilylprop-2-ynamides in the presence of KF-Al₂O₃ as catalyst. The corresponding terminal prop-2-ynamides were obtained in high yield in methanol at 25°C using 5 mol % of the catalyst (reaction time 20 min). Rise in temperature leads to the formation of Z,E-3-methoxyprop-2-enamides or 3,3-dimethoxypropanamides as a result of tandem desilylation-addition of methanol, depending on the conditions.     

Preparation of Some Glycosyl Amino Acid Building Blocks via Click Reaction and Construction of a Glycotetrapeptide Library Using Spot Synthesis

The copper-catalyzed 1,3-dipolar cycloaddition reaction between ethyl 2,3,4-tri-O-actetyl-6-azido-6-deoxy-1-thio-β -d-glucopyranoside (2), ethyl 2,3,4-tri-O-actetyl-6-azido-6-deoxy-1-thio-β -d-galactopyranoside (4), methyl 2,3,4-tri-O-acetyl-6-azido-6-deoxy-α -d-mannopyranoside (7), and methyl 2,3,6-tri-O-acetyl-2-azido-2-deoxy-β -d-glucopyranoside (9), and tert-butyl-protected Fmoc-asparaginic acid propargylamide (10) gave the corresponding protected glycosyl amino acid building blocks 11, 13, 15, and 17 in 67% to 95% yield. The latter were converted into the corresponding pentafluorophenyl esters 12, 14, 16, and 18, which were used for a spot synthesis of a combinatorial library containing 256 glycotetrapeptides. The library was screened for lectin-binding affinity with the lectins Concanavalin A (Con A), phaseolus vulgaris (PHA-E), and galantus nivalis (GNA).     

Steam Reforming Reactions of Methanol Over Nickel and Copper Catalysts

Steam-reforming reactions of methanol over NiO/Al₂O₃ and CuO/ZnO have been investigated. Over the nickel catalyst, the reaction rate is of zero kinetic order with respect to either methanol or steam, and the activation energy is 12.4 kJmol^?1, whereas with copper catalyst, the rate is expressed according to the literature as kP_a/(1 + K_aP_a + K_b+P_b) in which “a” and “b” are methanol and steam, respectively. The rate-controlling step of the reaction is assigned to the dissociation of O-H bond with dehydrogenation of C-H bond proceed rapidly to form carbon oxides. With copper catalyst the intrinsic participation of a water molecule during the dehydrogenation of C-H bond leads to the formation of carbon dioxide. With nickel catalyst, the dehydrogenation proceed more rapidly than the migration of a water molecule from an alumina site to a nickel site and causes almost exclusively the formation of carbon monoxide and hydrogen at a lower reaction temperature.     

Properties of surface compounds in methanol conversion on copper-containing catalysts based on CeO2 according to in situ IR-spectroscopic data

Formate and carbonate complexes and bridging and linear methoxy groups were detected on the surfaces of CeO₂ and 5.0% Cu/CeO₂ under the reaction conditions of methanol conversion using IR spectroscopy. The reaction products were H₂, methyl formate, CO, CO₂, and H₂O. The bridging and linear methoxy groups were the sources of formation of bi- and monodentate formate complexes, respectively. Methyl formate was formed as a result of the interaction of the linear methoxy group and the formate complex. The study demonstrated that the recombination of hydrogen atoms on copper clusters and the decomposition of methyl formate were the main reactions of hydrogen formation. Formate and carbonate complexes were the source of CO₂ formation in the gas phase, and the decomposition of methyl formate was the source of CO. It was found that the addition of water vapor to the reaction flow considerably decreased the rate of CO formation at a constant yield of hydrogen. The effects of water vapor and oxygen on the course of surface reactions and the formation of products are discussed. To explain the mechanism of methanol conversion, a scheme of surface reactions is proposed.     

CeCl3 · 7H2O‐KI‐Catalyzed,Environmentally Friendly Synthesis of N,N′‐Disubstituted Ureas in Water Under Microwave Irradiation

N,N′‐Disubstituted ureas were efficiently synthesized by reactions of urea with a variety of amines in water under microwave irradiation using CeCl₃ · 7H₂O‐KI as catalyst. This protocol has advantages of not using toxic phosgene and hazardous organic solvents, high reaction rate, high yield, and a simple workup procedure.     

Interaction of Methanol Spray and Water‐Deficit Stress on Photosynthesis and Biochemical Characteristics of Phaseolus vulgaris L. cv. Sadry

This study was a factorial experiment with a completely randomized design and three replications. The four levels of methanol spraying were used. Spraying was carried out three times during the growing season at 10‐day intervals beginning at 4 weeks after sowing. The spraying of solution continued until saturation of droplets on the leaves was achieved. The levels of water‐deficit stress applied were nonstress, moderate water stress and severe water stress. The results showed that there was a significant difference (P ≤ 0.05) between the methanol and water‐deficit stress treatments for chlorophyll (Chl) a and Chl b, carotenoid, total chlorophyll, net photosynthesis (P_N), intercellular CO₂ (C_i), maximal quantum yield of photosystem II photochemistry (F_v/F_m), leaf moisture, water use efficiency and relative water content. The application of foliar methanol at all levels of water‐deficit stress significantly decreased the catalase activity of the roots. Under all levels of water‐deficit stress, the 30% (v/v) methanol treatment significantly decreased peroxidase activity in the roots over that for the control. The results suggest that foliar application of methanol can decrease the negative effects of water‐deficit stress on Phaseolus vulgaris L. cv. Sadry.     

Eine semiempirische Gleichung zur Beschreibung des Lösungsmitteleinflusses auf Statik und Kinetik chemischer Reaktionen,Teil II: Praktische Anwendungen

Based on the model developed in Part I¹, equilibrium and rate data have been calculated for various chemical reactions in a variety of dipolar aprotic solvents of medium to high dielectric constants. Examples include solubility determinations, complex formation equilibria, ion pair equilibria and a nucleophilic substitution reaction with changes in the standard free energies of reaction or activation between about 3 and 8 kcal/mole. Experimental data were analyzed by the method of multiple linear regression. The physical meaning of the individual constants of the regression equations are discussed. Deviations observed between calculated and experimental free energies in structured solvents like water, methanol, formamide and N-methyl-formamide are indicative of changes in solvent structure associated with the solvation process and can be interpreted in terms of the structure making or breaking properties of the solutes.

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Teil I:U. Mayer, Mh. Chem.109, 421 (1978).     

Synthesis of amine-phenol ligands in water – a simple demonstration of a hydrophobic effect

Abstract

The synthesis in water of a series of tetradentate amine-phenol ligands derived from formaldehyde, 2,4-disubstituted phenols and amines is presented. These molecules, which are used in catalyst development, include 4,6-di-alkyl-2-bis(2-methoxyethyl)aminomethylphenols and 4,6-di-tert-amyl-2-bis(3-(dimethylamino)propyl)aminomethylphenols. Yields were generally greater than reactions performed in methanol and near quantitative for hydrophobic phenols.     

Bis-Thiourea Bearing Aryl and Amino Acids Side Chains and Their Antibacterial Activities

Abstract

A series of symmetrical 1,3-bis thiourea 1a–e and 1,4-bis thiourea derivatives 2a–e have been successfully synthesized from the reactions of amines with 3-acetylbenzoyl isothiocyanate and 4-acetylbenzoyl isothiocyanate, respectively. All the synthesized compounds were characterized by FT-IR spectroscopy and ¹H and ¹³C NMR spectroscopy. The compounds were screened for their antibacterial activity by turbidimetric method using gram-negative bacteria (E. coli ATCC 8739) using turbidimetric method. The newly synthesized bis-thiourea derivatives bearing aryl side chains showed good antibacterial activity against E. coli. The effect of the molecular structure of the synthesized compounds on the antibacterial activity is discussed.     

Catalytic Three‐Component Domino Reaction for the Preparation of Trisubstituted Oxazoles

Multicomponent reactions are attractive for assembling functionalized heterocyclic compounds. To this end, an efficient gold‐catalyzed three‐component domino reaction to form oxazoles directly from imines, alkynes, and acid chlorides is presented. The reaction proceeds in a single synthetic step by using a gold(III)–N,N′‐ethylenebis(salicylimine) (salen) catalyst to give trisubstituted oxazoles in up to 96 % yield. The substrate scope, a mechanistic study exploring the role of the gold catalyst, and the synthetic applications of the oxazole products are discussed.     

Selective alkylation of xylenes by alcohols on zeolite catalysts

The peculiarities of catalytic performance of crystalline aluminosilicates of different types and compositions (X, Y including dealuminated Y, mordenite, pentasil ZSM-5), as well as of amorphous aluminosilicate catalyst in conversion of xylene + alcohol mixtures were studied. New data were obtained for alkylation ofo-xylene withtert-butyl alcohol, concerning controlling the selectivity and stability of the zeolite catalysts in reactions proceeding with the participation of water, including the water evolved during the reaction, in particular by controlling the acidic properties and hydrophobycity of the zeolites. A catalyst ensuring production of 1,2-dimethyl-4-tert-butylbenzene (DMTBB) with a 94% yield and selectivity of alcohol conversion to the target product of 94–97% was developed. The catalyst can be used as the basis for a high-performance and environmentally safe method for the synthesis of DMTBB. The catalysts developed can be also used for selective alkylation ofo-xylene by C₃-C₅ alcohols and for alkylation ofm-xylene bytert-butyl alcohol.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp, 2912–2917, December, 1996.     

Spectral and luminescence properties and photochemical transformations of 7,7,9-trimethyl-6,7-dihydrofuro[3,2-<Emphasis Type="Italic">f</Emphasis>]quinoline

Spectral, luminescent, and photochemical properties of 7,7,9-trimethyl-6,7-dihydrofuro[3,2-f]quinoline (FDHQ) have been studied in hexane, alcohols, and water. Unlike 1,2-dihydroquinolines without the furo substituent, the fluorescence quantum yields for FDHQ in water and methanol are high (0.4 and 0.2, respectively), thereby indicating a difference in routes of excitation energy degradation in these compounds. The regularities in the FDHQ phototransformations have been studied by steady-state photolysis. The composition and the yield of final products depend on the presence or absence of oxygen in the system to a higher extent than on the solvent nature. This indicates the participation of the triplet excited state in the photo-chemical reactions in oxygen-free systems.     

Novel polycyclic heterocycles. XI. Synthesis of 11,12-dihydropyrido[2,1-b] [1,3]benzodiazepines, 6H-pyrido[1,2-c] [1,3,5]benzoxadiazepines,and 6H-Pyrido[1,2-c] [1,3,5]benzothiadiazepines

An unusually facile dehydrobromination, involving the ortho-bromine atom and the = NH proton of a 2-imino-1-(phenethyl)-, 2-imino-1-(phenoxymethyl)-, or 2-imino-1-(phenylthiomethyl)-pyridine ( 2a-e ) has led to the synthesis of three novel bridgehead nitrogen tricyclic systems: 11,12-dihydropyrido[2,1-b] [1,3]benzodiazepines ( 3a,b ), 6H-pyrido[1,2-c] [1,3,5]benzoxadiazepines ( 3c,d ) and 6H-pyrido[1,2-c][1,3,5]benzothiadiazepines ( 3e ). As anticipated, these cyclizations required a base, e.g., potassium carbonate, and a catalyst, e.g., copper bronze. What was unusual, was that these reactions occurred in methanol or n-propanol, under reflux, either under anhydrous conditions, or in the presence of large amounts of water. The pmr spectra of these compounds are discussed.     

Reduction of 2-amino-1-(4-nitrophenyl)-1 H-pyrido[3,2-b]indole-3-carbonitrile by sodium borohydride and sodium cyanoborohydride

The reduction of pyridoindole derivative 1 by sodium borohydride in methanol gives 4,5-dihydropyridoindole 2. On treatment of 5H-pyrido[3,2-b]indolium chloride 3 with sodium cyanoborohydride in methanol in the presence of hydrogen chloride, reduction of the pyridine ring is accompanied by reduction of the CN group, resulting in the formation of tetrahydropyridoindole 4. Compound 4 reacts with DMF dimethyl acetal to yield amidine 6, and refluxing of 4 with acetic anhydride results in tetrahydropyridine ring cleavage yielding indolylacrylonitrile 9. The hydrochloride and chloride of compounds 4 and 6 were obtained