Showing papers on "Substituent published in 1975"

Dispersants and process for their preparation

Abstract: Compositions useful as lubricant and fuel dispersants are prepared by reacting a hydroxyaromatic compound containing an aliphatic or alicyclic substituent which has at least about 6 carbon atoms with an aldehyde in the presence of an alkaline reagent and at a temperature up to about 125°C., substantially neutralizing the resulting intermediate at a temperature up to about 150°C., and then reacting with a primary or secondary amino compound.

4-Trifluoromethylimidazoles and 5-(4-pyridyl)-1,2,4-triazoles, new classes of xanthine oxidase inhibitors.

Abstract: The syntheses of a number of 2-substituted 4-trifluoromethylimidazoles and 3-substituted 5-(4-pyridyl)-1,2,4-triazoles are described. The trifluoromethylimidazoles were prepared from 3,3-dibromo-1,1,1-trifluoroacetone after hydrolysis with aqueous sodium acetate solution and condensation with an aldehyde in the presence of ammonia. Basic hydrolysis of the trifluoromethyl group was found to provide a facile method for the synthesis of imidazole-4-carboxylic acids. In the imidazole series a 2-aryl substituent and a free imino group were required for xanthine oxidase inhibitory activity. The triazoles were obtained through the reaction of an aroylhydrazine and an imino ether followed by thermal ring closure of the intermediate acylamidrazone. As in the imidazole series, a free imino group is an absolute requirement for in vitro activity. Additional structure-activity relationships of these compounds are presented.

Oil recovery method using a surfactant

Abstract: A method is disclosed for recovering oil from a subterranean oil-bearing formation wherein a liquid solution in injected into and driven through the formation and oil is recovered from the formation. The liquid solution contains an effective amount of a surface-active agent having the general formula: ##EQU1## or ##EQU2## wherein R1 is a benzene, toluene, or xylene radical having a linear or branched alkyl substituent containing from 6 to 24 carbon atoms; R2 is an alkyl, cycloalkyl, alkene or aryl radical containing up to 8 carbon atoms; R3 is a hydrogen atom, a hydroxyl radical, or an aliphatic radical containing from 1 to 8 carbon atoms; n has a value of 2 or 3; m has an average value of from 1 to 20; and X is a cation.

Photoelectron spectra and bonding in phosphorus compounds

Abstract: The results of (low energy) photoelectron spectroscopy render possible a better appreciation of bonding in molecules. The application of the new experimental method is demonstrated utilizing representative phosphorus compounds, and the close symbiosis delineated with molecular orbital models. Among the topics discussed are: the element P4, phosphine PH3 and derivatives, phosphorus substituent effects in organic compounds and phosphorus multiple bonding. ‘Actually, everything is much more complicated’2

Stereochemical aspects of the interaction between steroidal diamines and DNA

Abstract: A complete series of stereoisomeric quaternised diaminoandrostanes, differing in their stereochemistry at the 3,5 and 17 positions, has been examined for effects on the thermal denaturation of calf thymus DNA and for the ability to remove and reverse the supercoiling of closed circular duplex PM2 DNA. In both types of test the eight isomers rank in the same order of effectiveness. The preferred stereochemistry for the quaternary substituents at positions 3 and 17 is beta; of these the orientation of the 17- substituent is more critical. Folding of the steroid skeleton between the A and B rings, as in 5beta-androstanes, diminishes effectiveness but does not necessarily abolish the effect on supercoiling. The over-riding importance of the C-D ring end of the steroid nucleus bearing a 17beta-amino substituent is confirmed by a comparison of the effects of five mon-amino androstanes. Relative helix=unwinding angles per bound steroidal diamine molecule have been determined for four of the isomers; for three 17beta compounds the estimated values are similar to that previously reported for irehdiamine A. For a fourth isomer the angle is 0.22 times that of ethidium, the lowest yet determined for any DNA-binding drug. The results lend further support to the argument that intercalation can be reled out, and alternative models for the binding mechanism are discussed.

Electronic structures of cephalosporins and penicillins. 4. Modeling acylation by the beta-lactam ring.

Abstract: Molecular orbital calculations by the CNDO/2 method are used to study the molecular and electronic details involved in the initial phases of the opening of the beta-lactam ring of a model cephalosporin structure, 7-amino-3-acetoxymethyl-3-cephem. The effect of a simple nucleophile, OH-, approaching the carbonyl carbon center of the beta-lactam ring is monitored by following the charge redistributions that occur in the bicyclic system and in the 3 side chain. A migration of electron density to the ester oxygen of the CH2OAc group is observed with concomitant weakening of the CH2-OAc bond. The results are discussed in relation to the mechanism of acylation of bacterial cell wall enzymes by beta-lactam antibiotics and in relation to the hydrolysis of these molecules. The results indicate that the ability of the 3' substituent of cephalosporins to stabilize electron density transferred to it, i.e., the leavability of the 3' moiety, can be an important factor in activating the beta-lactam toward nucleophilic attack.

Carbon‐13 NMR spectra of coumarin and methoxycoumarins—a reinvestigation of charge density/Chemical Shift Relations

Abstract: The carbon-13 NMR spectra of coumarin, 6-, 7-, 8-methoxycoumarin, and 5,7-, 7,8-, 5,8- and 6,7-dimethoxycoumarin have been measured and assigned. It is shown that substituent induced chemical shifts S(δ) in the mono- and disubstituted systems correlate well with the HMO atom-atom polarisibilities πij of the parent compound: Si(δi) = 80.13 πij with a standard deviation of 1.42 ppm and a correlation factor of 0.994. Correlations between δ(13C) values and charge densities calculated by various semi-empirical methods are less successful.

A new parenteral cephalosporin. sk&f 59962: 7-trifluoromethylthioacetamido-3-(1-methyl-1h-tetrazol-5-ylthiomethyl)-3-cephem-4-carboxylic acid. chemistry and structure activity relationships

Abstract: The synthesis, microbiological profile and in vivo effectiveness in laboratory animals of a series of cephalosporins having 7-acyl substituents derived from methylthioacetic acid are described. Structure-activity relationships examined include the effect of oxidation of the side-chain sulfur atom, replacement of the (side-chain) methyl hydrogens by fluorine and replacement of the 3-acetoxy substituent by thioheterocycles. One derivative, 7-trifluoromethylthioacetamido-3-(1-methyl-1H-tetrazol-5-ylthiomethyl)-3-cephem-4-carboxylic acid (SK&F 59962), was found to have outstanding antibacterial activity in vitro and in vivo.

Pyrolysis of aryl azides. III. Steric and electronic effects upon reaction rate

Abstract: First-order rate constants have been measured for the pyrolysis of 15 phenyl azides in decalin solution. The rate for phenyl azide is increased only slightly by all para and many ortho substituents; in these cases Eact and ΔSact values are related linearly. The very large rate increases when the ortho substituent is phenylazo, nitro, acetyl or benzoyl cannot be from steric or normal electronic effects and therefore identify a specific involvement of these groups in the transition state. This rate enhancement is reduced to scarcely significant levels by a 6-chloro or 6-methyl group in 2- nitrophenyl azide, but not by a 6-nitro group. These results raise doubts about recent claims1 to establish mechanism by measuring polar effects on rates of pyrolysis of azides in which steric effects might also operate.

The Rearrangement of Aryl Thiohydrazonates

Abstract: Rearrangement and cyclization of a series of p-nitrophenyl and heteroaryl thiohydrazonates ArSCAr′ = NNHC6H3XY(2,4), where the displaced substituent X is Br or F and the remaining substituent Y is ...

Molecular orbital theory of the hydrogen bond. X. Monosubstituted carbonyls as proton acceptors

Abstract: Ab initio SCF calculations with a minimal STO−3G basis set have been performed to determine equilibrium structures and energies for a series of mixed dimers formed from water and substituted carbonyl compounds. These dimers may be represented by the general formula HOH⋅⋅⋅OCHR, where R may be CH3, NH2, OH, F, CHO, and C2H3. For each dimer in this series except water−formic acid, two equilibrium structures have been found, in which the substituent R is ’’cis’’ or ’’trans’’ to the proton donor water molecule with respect to the carbonyl CO bond. Except for a cyclic equilibrium water−formamide dimer, all equilibrium dimers have open−chain trans structures consistent with the General Hybridization Model. There is only a small variation in the hydrogen bond energies of equilibrium dimers HOH⋅⋅⋅OCHR, except for the water−formamide dimers which are significantly more stable than all others in this series. The structures and energies of the equilibrium dimers HOH⋅⋅⋅OCHR have been analyzed in terms of the effect of...

Nuclear Magnetic Resonance Spectroscopy. Carbon-13 Spectra of Some Macrolide Antibiotics and Derivatives. Substituent and Conformational Effects

Abstract: Carbon-13(^(13)C NMR) chemical shifts are reported and assigned for a series of naturally occurring macrolide antibiotics, biosynthetic precursors, shunt metabolites, and derivatives. Besides the usual ^(13)C NMR substituent effects, the results are interpreted with reference to conformational models proposed for these compounds. A number of proposals are made concerning the conformations of the various derivatives, the differences between them, and the possibility of internal motion. The usefulness of ^(13)C NMR in ascertaining hydrogen bonding and in the structural analysis of these important cornpounds is demonstrated.

Inclusion complexes of cinnamic acids with cyclodextrins. Mode of inclusion in aqueous solution.

Abstract: Inclusion complexation of various trans- and cis-cinnamic acid derivatives with α-and β-cyclodextrins in aqueous solution was studied by circular dichroism (CD), ultraviolet (UV), and nuclear magnetic resonance (NMR) spectroscopies By the analyses of the induced CD and UV spectral changes, the spatial relationships between guest and host molecules was investigated To elucidate the inclusion mechanism, stoichiometric ratio, which was found 1 : 1, formation constant, and thermodynamic parameters for trans-cinnamic acid-cyclodextrin systems were determined Various factors in guest molecule such as ionization, hydrophobic nature, and substituent effect were reflected in inclusion formation From the evidences of sign of the induced CD and NMR chemical shift, it was proposed that phenyl moiety of cinnamic acid was fixed into (R)-configuration within the cavity of cyclodextrin

Restricted Rotation Involving the Tetrahedral Carbon. XIV. Conformational Equilibria and Attractive Interactions in Substituted 9-Benzyltriptycenes

Abstract: Several 9-benzyltriptycene derivatives were prepared by addition of benzynes to 9-benzylanthracenes. Rotation about the C9–Cbenzyl bond of compounds with a substituent at a peri-position to the benzyl group was found to be frozen at low temperatures on the NMR time scale but not at room temperature. In contrast, compounds with two substituents at two peri-positions to the benzyl group showed a frozen rotation about the C9–Cbenzyl bond at room temperature. Distribution of the conformers, as judged from the PMR intensities, showed preference to the dl-isomers in spite of the fact that they are the ones which are highly disfavored by steric effects. Interpretation of the phenomenon was based on the fact that attractive interactions, mainly charge-transfer type, exist between the substituted benzo group in the triptycene skeleton and the benzene ring in the benzyl group.

Carbon-13 Nuclear Magnetic Resonance Studies of Compounds of the Vitamin B6 Group and Related Pyridine Derivatives

Abstract: The I3C chemical shifts and 13C–31P spin–spin couplings (where applicable) are reported for pyridoxine, pyridoxamine, pyridoxal, pyridoxamine phosphate, and pyridoxal phosphate. Resonance assignments are made by consideration of substituent chemical shift effects, as tested on an analogous series of pyridine derivatives. Increased shielding of the C4′ and C5′ methylene groups of the vitamin B6 compounds and the methyl groups of 3,4-dimethylpyridine relative to the predicted values are attributed to steric compression. In aqueous solution pyridoxal exists as the hemiacetal form, although at high pH it is in rapid equilibrium with a significant amount of the aldehyde form. Pyridoxal phosphate exists as the aldehyde at high pH, as the hydrated aldehyde at low pH, and in a slow equilibrium between detectable amounts of both species at pH 4. The 13C–31P couplings through two bonds lie in the range 4.5 ± 0.5 Hz found for a variety of other organic phosphates. The couplings through three bonds indicate a prefere...

Certain biphenyl derivatives used to treat disorders caused by increased capillary permeability

Abstract: Pharmaceutical compositions the essential active ingredient of which is a biphenyl derivative, at least one of the phenyl nuclei of which has two adjacent hydroxyl groups, the two phenyl nuclei being separated by a carbon chain having one or two carbon atoms and in general, a double bend between two chain carbon atoms or between a chain carbon atom and a substituent thereof. The compositions are useful for the treatment of disorders of the blood micro-circulation.

Carbon-13 Nuclear Magnetic Resonance Spectra of Isothiazole, 1,2-Dithiole, and 1,3-Dithiole Derivatives

Abstract: Carbon-13 chemical shift data have been obtained for a number of isothiazole, benzo[c]isothiazole, 1,2-dithiole, and 1,3-dithiole derivatives. A number of these compounds are thiones and the chemical shifts of the C=S carbons are discussed in the light of recent attempts to predict such chemical shifts from those of the analogous carbonyl compounds. Comparisons of substituent chemical shift (s.c.s.) effects in these heterocyclic compounds with those in simpler aromatic or conjugated systems have been made and additivity correlations tested in a number of cases.