Knoevenagel condensation of 2-carbethoxycyclohexanone and malononitrile: Synthesis of 4-cyano-3-ethoxy-1-hydroxy-5,6,7,8-tetrahydroisoquinoline, an isomer of the abnormal product

The structure of the abnormal product 1a formed in the Knoevenagel condensation of 2-carbethoxycyclohexanone and malononitrile has been further confirmed. Oxidation of the tetrahydroisoquinoline 3b using Na2Cr2O-AcOH-H2SO4 gave the keto isoquinoline 3d and the isoquinoline-1-carboxylic acid 5a. The acid chloride of 5a was condensed with diethyl ethoxymagnesiomalonate to afford after decarbethoxylation the methyl ketone 5d which on Baeyer-Villiger oxidation gave a mixture of the acetate 1g and the title compound 1b. The unambiguous synthesis of 1b confirms the structure assigned earlier to the title compound also formed during the partial hydrolysis of the diethoxy compound 1c. Condensation of 2-acetylcyclohexane-1,3-dione with malononitrile gave the quinoline derivative 4c which on ethylation yielded the ketoquinoline 4d. The present studies have confirmed that the quinoline compound 4a is also formed in the condensation of 2-acetylcyclohexanone and cyanoacetamide.

Bufadienolides. 8. 12(13→14)abeo skeletal rearrangements

Several methods were developed for converting isodigitoxigenin (2a) into methyl acetals 4b and 4c. Of these, methanolysis (followed by acetylation) of isodigitoxigenin in the presence of p-toluenesulfonic acid proved most useful. Each isomer reached an equilibrium corresponding to ca. 3:1 acetal 4c to 4b within 15 min in benzene containing p-toluenesulfonic acid. Addition of dihydropyran to the equilibrium mixture resulted in excellent conversion into vinyl ether 5a. Heating either acetal 4b or 4c in benzene containing p-toluenesulfonic acid led to a skeletal rearrangement culminating in formation of C-norcardenolide 6. In addition to results of physical measurements, the structure of spiran 6 was confirmed by degradation to methyl ketone 8. Similar rearrangement of isodigitoxigenin gave spiran 9 accompanied by C-norcardenolide 6. Treating lactone 9 with p-toluenesulfonic acid in methanol-water provided acetals 10a and 10b, which on further contact with p-toluenesulfonic acid in refluxing benzene gave lactone 9 and cardenolide 6. Evidence underlying the stereochemical assignments noted for structures 4, 9, and 10 was also discussed.

Methyl ethyl ketone plus water plus secondary butyl alcohol: A potential system for the exploration of a quadruple critical point

We report preliminary experiments on the ternary-liquid mixture, methyl ethyl ketone (MEK)+water (W)+secondary butyl alcohol (sBA)-a promising system for the realization of the quadruple critical point (QCP). The unusual tunnel-shaped phase diagram shown by this system is characterized and visualized by us in the form of a prismatic phase diagram. Light-scattering experiments reveal that (MEK+W+sBA) shows near three-dimensional-Ising type of critical behavior near the lower critical solution temperatures, with the susceptibility exponent (gamma) in the range of 1.217 <=gamma <= 1.246. The correlation length amplitudes (xi(o)) and the critical exponent (nu) of the correlation length (xi) are in the ranges of 3.536 <=xi(o)<= 4.611 A and 0.619 <=nu <= 0.633, respectively. An analysis in terms of the effective susceptibility exponent (gamma(eff)) shows that the critical behavior is of the Ising type for MEK concentrations in the ranges of 0.1000 <= X <= 0.1250 and X >= 0.3000. But, for the intermediate range of 0.1750 <= X < 0.3000, the system shows a tendency towards mean-field type of critical behavior. The advantages of the system (MEK+W+sBA) over the system (3-methylpyridine+water+heavy water+potassium Iodide) for the realization of a QCP are outlined.

Vapor-liquid equilibriums: systems methyl ethyl ketone-p-xylene and chlorobenzene-p-xylene

Vapor-liquid equilibrium data have been measured for the binary systems methyl ethyl ketone-p-xylene and chlorobenzene-p-xylene, at 685 mmHg pressure. The activity coefficients have been evaluated taking Into consideration the vapor-phase nonideallty. The f-x-y data have been subjected to a thermodynamic consistency test and the activity coefficients have been correlated by the Wilson equation.

Metabolism of a monoterpene ketone, R-(+)-pulegone—a hepatotoxin in rat

R-(+)-Pulegone was administered orally to rats and the urinary metabolites were investigated. Six metabolites were isolated and purified using column and thin layer chromatographic techniques. Metabolites were identified by i.r., n.m.r. and mass spectral analyses.The neutral metabolites isolated from urine of rats treated with pulegone (I) were: pulegol (II), 2-hydroxy-2(1'-hydroxy-1'-methylethyl)-5-methylcyclohexanone (III), 3,6-dimethyl-7a-hydroxy-5,6,7,7a-tetrahydro-2(4H)-benzofuranone (V) and menthofuran (VII). Metabolites II and III were also excreted in conjugated form.Acidic metabolites isolated from urine of rats treated with pulegone (I) were: 5-methyl-2(1'-methyl-1'-carboxyethylidene)cyclohexanone (IV) and 5-methyl-5-hydroxy-2(1'hydroxy-'-carboxyethyl)cyclohexanone (VI).

Destruction Of Rat-Liver Microsomal Cytochrome-P-450 Invitro By A Monoterpene Ketone, Pulegone A Hepatotoxin

Significant destruction (68%) of liver microsomal cytochrome P-450 and homogeneous cytochrome P-450 purified from PB-treated rats is noticed upon incubation with 10 mM pulegone at 37-degrees-C for 30 min. There is also a concomitant loss of heme. The destructive phenomenon does not require metabolic activation of pulegone. The destruction of purified cytochrome P-450 is time-dependent and saturable. Structure-activity studies suggest that an alpha-isopropylidine ketone unit with a methyl positioned para to the isopropylidine group as in pulegone is necessary for the in vitro destruction of cytochrome P-450. SKF-525A at a concentration of 4-mM obliterates the destruction of cytochrome P-450 by pulegone. Experiments with C-14-pulegone suggest that pulegone or its rearranged product binds covalently to the prosthetic heme of cytochrome P-450.

Studies on the metabolism of a monoterpene ketone, R-(+)-pulegone-a hepatotoxin in rat: isolation and characterization of new metabolites

1. The metabolic disposition of R-(+)-pulegone (1) was examined in rats following four daily oral doses (250 mg/kg). 2. Six metabolites, namely pulegol (II), 2-hydroxy-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanone (III), 3,6-dimethyl-7a-hydroxy-5,6,7,7a-tetrahydro-2(4H)-benzofuranone (IV), menthofuran (V), 5-methyl-2-(1-methyl-1-carboxyethylidene)cyclohexanone (VI), and 5-methyl-5-hydroxy-2-(1-hydroxy-1-carboxyethyl)cyclohexanone (VII) have previously been isolated from rat urine, and identified (Moorthy et al. (1989a). Eight new metabolites have now been isolated from rat urine, namely, 5-hydroxy-pulegone (VIII), piperitone (IX), piperitenone (X), 7-hydroxy-piperitone (XI), 8-hydroxy piperitone (XII), p-cresol (XIII), geranic acid (XIV) and neronic acid (XV). These were identified by n.m.r., i.r. and mass spectrometry. 3. Based on these results, metabolic pathways for the biotransformation of R-(+)-pulegone in rat have been proposed.

Photochemical intramolecular gamma-hydrogen abstraction in a ketone and an alkene and the role of tunneling of hydrogen

Intramolecular gamma-hydrogen abstraction reactions were examined in pentane-2-one and 2-methyl-1-pentene in their lowest triplet states using the AM1 semi-empirical molecular orbital method with the complete geometry optimization in the unrestricted Hartree-Fock frame. The results reveal that the oxygen atom of the carbonyl group and the end carbon atom of the olefinic bond acquire high free valence and spin density indices in their respective lowest triplet states, leading to abstraction of hydrogen from the gamma-position relative to the carbonyl and olefinic bonds. The theoretical energy profiles fit with a polynomial and the probability of tunneling of hydrogen was estimated by the WKB (Wentzel, Kramer and Brillouin) method. The results, after thermal averaging of the rate constants, reveal that tunneling of hydrogen is significant at room temperature.

ChemInform Abstract: Synthesis Based on Cyclohexadienes. Part 16. Synthesis of Methyl 2,7-Dimethyltricyclo (5.2.2.01,5)undec-5-ene-6-carboxylates

Synthesis of methyl 2, 7-dimethyltricyclo{5.2.2.0(1,5}undec-5-en-6-carboxylates, the tricyclic skeleton present in (+)-allo-cedrol (1) is described using the Diels-Alder strategy. Thus, Birch reduction of the aromatic acid 8 gives 5, the methyl ester of which is isomerised with DBU to a 1:1 mixture of the dienes 6 and 4. Cycloaddition of this mixture with 2-chloroacrylonitrile followed by hydrolysis yields the ketone 60 having the tricyclo{5.2.2.0(1.5)}undec-5-ene framework. Similar reaction with methyl vinyl ketone affords the regioisomeric adducts 61 and 62.

Gas Phase Oxygen Quenching Studies of Ketone Tracers for Laser-Induced Fluorescence Applications in Nitrogen Bath Gas

In this paper we report the quantitative oxygen quenching effect on laser-induced fluorescence of acetone, methyl ethyl ketone, and 3-pentanone at low pressures (approximate to 700torr) with oxygen partial pressures up to 450torr. Nitrogen was used as a bath gas in which these molecular tracers were added in different quantities according to their vapor pressure at room temperature. These tracers were excited by using a frequency-quadrupled, Q-switched, Nd:YAG laser (266nm). Stern-Volmer plots were found to be linear for all the tracers, suggesting that quenching is collisional in nature. Stern-Volmer coefficients (k(sv)) and quenching rate constants (k(q)) were calculated from Stern-Volmer plots. The effects of oxygen on the laser-induced fluorescence of acetone, methyl ethyl ketone, and 3-pentanone were compared with each other. Further, the Smoluchowski theory was used to calculate the quenching parameters and compared with the experimental results.

A promising ketone containing alternating copolymer for organic photovoltaics

An alternating copolymer containing dithienylcyclopentadienone, thiophene and benzothiadiazole was synthesized by palladium (0) catalyzed Stille coupling reaction. Structural characterization of the synthesized alternating copolymer was carried out by NMR and FTIR spectroscopy. This solution processable copolymer shows an excellent thermal stability and has a broad absorption range from 300-800 nm. High LUMO energy level and low band gap of the synthesized copolymers suggest that, this copolymer will be a better donor material for application in organic photovoltaics. Particle size analysis and molecular weight determination of the synthesized copolymer through dynamic light scattering experiment indicates that, high molecular weight copolymer was obtained by this polymerization route. Photovoltaic devices were fabricated from the blend of copolymer and phenyl-C61- butyric acid methyl ester as the active material. Fabricated photovoltaic device results show that this alternating copolymer is a promising candidate for use in organic photovoltaics.

Photocatalytic and Thermal Degradation of Poly(methyl methacrylate), Poly(butyl acrylate), and Their Copolymers

The photocatalytic and thermal degradations of poly(methyl methacrylate), poly(butyl acrylate), and their copolymers of different compositions were studied. The photocatalytic degradation was investigated in o-dichlorobenzene in the presence of two different catalysts, namely, Degussa P-25 and combustion synthesized nanotitania (CSN-TiO2). The samples were analyzed by using gel permeation chromatography (GPC) to obtain the molecular weight distributions (MWDs) as a function of reaction time. Experimental data indicated that the photodegradation of these polymers occurs by both random and chain end scission. A continuous distribution kinetic model was used to determine the degradation rate coefficients by fitting the experimental data with the model. Both the random and specific rate coefficients of the copolymers decreased with increasing percentage of butyl acrylate (BA). Thermal degradation of the copolymers was investigated by thermo-gravimetry. The normalized weight loss profiles for the copolymers showed that the thermal stability of the copolymers increased with mole percentage of BA in the copolymer (PMMABA). The Czawa method was used to determine the activation energies at different conversions. At low acrylate content in the copolymer, the activation energy depends on conversion, indicating multiple degradation mechanisms. At high acrylate content in the copolymer, the activation energy is independent of conversion, indicating degradation by a one-step mechanism.

Methyl 1H-1,2,3-triazole-4-carboxylate

The title compound, C4H5N3O2, features an essentially planar molecule (r.m.s. deviation for all non-H atoms = 0.013 angstrom). The crystal structure is stabilized by intermolecular N-H center dot center dot center dot O hydrogen bonds and pi-pi stacking interactions (centroid centroid distance 3.882 angstrom).

Solid state stacked trimers of 1,10-phenanthroline in a supramolecular tubular motif of C-methyl calix[4]resorcinarene

The self-assembly of bidentate ligand, 1,10-phenanthroline with C-methyl calix[4]resorcinarene (CMCR) in presence of coumarin results in a unique trimer stacking arrangement of phenanthroline molecules in a nanotubular motif generated by the supramolecular assembly of the host.

Reversible Insertion of Methyl Isothiocyanate into Copper(I)Aryloxides

MeNCS undergoes insertion into the copper(I)-aryloxide bond to form [N-methylimino(aryloxy)methanethiolato]-copper(I) complexes. This insertion occurs in the absence of ancillary ligands unlike the analogous insertion of PhNCS. The reaction with 4-methylphenoxide results in the formation of hexakis[[N-methylimino(4-methylphenoxy) methanethiolato]copper(I)] (1), which has been characterized by X-ray crystallography. Crystal data for 1: hexagonal , a = 12.365(3) Angstrom, c = 36.734(16) Angstrom, gamma = 120 degrees, Z = 3, V = 4863(3) Angstrom(3), R = 0.0306. Reactions of 2,6-dimethyl- and 4-chlorophenoxides also result in analogous copper(I) complexes 2 and 3. Addition of stochiometric amounts of PPh(3) to the oligomeric complexes typically results in the extrusion of MeNCS. The ease of extrusion is dependent on the substituents on the aryloxide, and this deinsertion is accelerated by water. However, the extrusion reaction is slow enough in the case of the N-methylimino(2,6-dimethylphenoxy)-methanethiolate complex and the isolation of an intermediate monomeric product bis(triphenylphosphine)[N-methylimino(2, 6-dimethylphenoxy)methanethiolato] copper(I) (4) is possible. Crystal data for 4: triclinic , a = 10.088(2) Angstrom, b = 11.302(1) Angstrom, c = 17.990(2) Angstrom, alpha = 94.06(1)degrees, beta = 95.22(2)degrees, gamma = 103.94(1)degrees, Z = 2, V = 1974.4(7) Angstrom(3), R = 0.0361. In the presence of of PPh(3), the insertion reaction becomes reversible. This allows the exchange of the heterocumulene MeNCS or the aryloxy group in these molecules with another heterocumulene or a phenol, respectively, when catalytic amounts of PPh(3) are added. Oligomers with exchanged heterocumulmes and phenols could be characterized by independent synthesis.