Showing papers on "Substituent published in 1984"

Substituent effects in the electropolymerization of aromatic heterocyclic compounds

Abstract: Oxydation electrochimique de l'indole, d'indoles substitues et de thianaphtene donnant des polymeres semiconducteurs avec des conductivites de 10 −2 ohm −1 cm −1 . Les effets electroniques induits par les substituants sont etudies par calculs d'orbitale moleculaire INDO

Synthesis of Branched-Chain Sugars

Abstract: Publisher Summary This chapter provides an overview of the synthesis of branched-chain sugars. The naturally occurring, branched-chain sugars were classified as rare sugars until the 1960's, but the discovery of numerous new sugars as the glycosidic component of antibiotics during the past two decades has stimulated extensive research on their chemistry and biochemistry. Most of the branched sugars found in Nature have a polar substituent at the branching carbon-atom (Type A); tertiary alcohols are commonest, but some of them are in the form of a methyl ether, acetate, or cyclic carbonate and, in several instances, an amino or a nitro group is attached to the tertiary carbon atom. Diversity is observed in the branchings, but some of them are chemically interconvertible and also can be derived from a common intermediate. This chapter explains the concepts related to the nucleophilic reactions of sugar oxiranes, aldol addition, and cyclization of dialdehydes with nitroalkanes. It also presents a brief discussion on methyl-branched sugars and two-carbon-branched sugar.

Substituent effects on the stability of three-electron-bonded radicals and radical ions from organic sulfur compounds

Abstract: Effet des substituants inducteurs d'electrons R sur la stabilite de (R 2 S...SR 2 ) + , (RS...SR) − et R 2 S...B 2 . L'etude est faite par radiolyse pulsee

Synthesis of biological markers in fossil fuels. 2. Synthesis and carbon-13 NMR studies of substituted indans and tetralins

Abstract: Synthese d'une serie de methyl-, ethyl-, propyl-, butyl indanes et tetralines par la methode de Kumada impliquant la reaction d'halogenures d'aryle ou de vinyle avec des reactifs de Grignard en presence du chlorure de [bis(diphenylphospino)-1,3 propyl] nickel II. On etudie ces composes par spectrometrie RMN du 13 C

Synthetic studies on the avermectins: substituent effects on intramolecular Diels-Alder reactions of N-furfurylacrylamides and further reactions of the cycloadducts

Abstract: samples at 80 K. The C-C band at 1558 cm-' represents the initial all-trans pigment while that at 1575 cm-* almost certainly arises from the short-wavelength M-type intermediate absorbing at ca. 380 nm. The results agree with previously determined correlation between A, and C=C stretching frequency and expected temperature dependence of M formation.12 On combination of the 6-cis and 2,6-dicis isomers of 2-4 with bacterioopsin, a broad absorption is noted with a A, , of 450-460 nm with a shoulder at 510 nm. Extraction of the pigment with methylene chloride yields the respective 6-cis or 2,6-dicis isomer. These pigments are rapidly (5 min) destroyed by hydroxylamine or all-trans-retinal. On irradiation, the absorption shifts to 487 nm, increases in intensity, and is identical with that of the all-trans pigments. Only the respective all-trans isomer is obtained when these irradiated pigments are extracted with methylene chloride. These results indicate that an unstable associate of the 6-cisand 2,6-dicis-2-4 retinals and bacterioopsin is formed, possibly allowed by the lack of the cyclohexyl ring and thus the greater flexibility of the chromophore. The above experiments demonstrate that these acyclic chromophores can form pigments with bacterioopsin which show light-induced absorption and pH changes. As these retinal derivatives lack both a cyclohexyl ring and the fifth C=C, neither of these structural elements are evidently essential for these functions of the pigment. A similar but more restrictive conclusion has been proposed for the 5,6-ethylene bond by our studies of the 5,6-dihydroretinal pigments.13 These results are consistent with isomerization and charge separation being thd primary event14 and indicate that the proton pumping and photocycling are dependent on the polyene chain portion of the retinal chromophore.

Gaba esters and gaba analogue esters

Abstract: Ester derivatives of gamma-aminobutyric acid (GABA) and GABA analogues which cross the blood-brain barrier are disclosed, as well as methods of synthesizing and using the compounds. The ester derivatives have the formula: ##STR1## where A is a radical compound having at least one esterifiable OH group; n varies from one to the total number of esterifiable OH group contained in A; and R1, R2, R3 and R4 are hydrogen or a substituent.

Herbicidal cyclohexane-1,3-dione derivatives

Abstract: The invention concerns compounds of formula I ##STR1## wherein: X and Y are independently selected from the group consisting of hydrogen, C 1 to C 4 alkyl, C 1 to C 4 haloalkyl, and the group wherein X and Y together from a three or four-membered carbon bridge the bridge optionally comprising one or both of a double bond and a carbonyl group; Z is selected from the group consisting of hydrogen, halogen, C 1 to C 4 alkyl and C 1 to C 4 alkanoyl; R 1 is selected from the group consisting of: hydrogen; an acyl group; and an inorganic or organic cation; R 2 is selected from the group consisting of: C 1 to c 6 alkyl; C 2 to C 6 alkenyl; C 2 to C 6 haloakenyl; C 2 to C 6 alkynyl; and substituted C 1 to C 6 alkyl wherein the alkyl group is substituted with a substituent selected from the group consisting of halogen, phenyl, and substituted phenyl wherein the benezene ring is substituted with from one to three substituents selected from the group consisting of halogen, and C 1 to C 6 alkyl; R 3 is selected from the group consisting of: C 1 to C 6 alkyl; and R 4 is selected from the group consisting of: hydrogen; C 1 to C 6 alkyl; and (C 1 to C 6 alkoxy) carbonyl. The compounds are herbicides and in further embodiments the invention provides processes for the preparation of compounds of formula I, herbicidal compositions comprising the compounds of formula I and processes for severly damaging or killing unwanted plants by application of compounds of formula I.

Molecular Requirements for the Mutagenicity of Malondialdehyde and Related Acroleins

Abstract: Malondialdehyde, a product of lipid peroxidation and prostaglandin biosynthesis, is mutagenic in Salmonella . To determine the molecular requirements for its mutagenicity, we tested a series of β-substituted acroleins in Salmonella typhimurium hisD3052. Mutagenicity is dependent on the steric bulk of the substituent (revertants/µmol) at the β position: β-methoxyacrolein, 220; β-ethoxyacrolein, 110; and β-isobutoxyacrolein, 40. A good leaving group at the β position substantially increases the mutagenic activity (revertants/µmol): β-( p -nitrophenoxy)acrolein, 620; β-benzoyloxyacrolein, 320; β-chloroacrolein, 890; and di-γ-oxopropenyl ether, 870. These data suggest that nucleophilic attack on the β-carbon followed by elimination of the β substituent is important for mutagenicity. Substitution of a methyl group at the α-carbon abolishes mutagenicity of these compounds. This effect can be explained by the lack of chemical reactivity of the α-methyl analogues toward oxygen or nitrogen nucleophiles. Propynal, which can add nucleophiles to generate a substituted acrolein, exhibits the highest mutagenicity (1370 revertants/µmol) in this series. The importance of the aldehyde functionality is suggested by the nonmutagenicity of propiolonitrile, ethylpropiolate, 4-benzoyloxy-3-buten-2-one, and 4-methoxy-3-buten-2-one. Aldehyde addition subsequent to the formation of the Michael adduct is, therefore, important for mutagenesis. An investigation of the toxicity of the present series indicates that toxicity and mutagenicity are independent events based on different chemical reactions.

The thermal isomerization of azobenzenes. III. Substituent, solvent, and pressure effects on the thermal isomerization of push-pull azobenzenes

Abstract: The substituent, solvent, and pressure effects on the rate of the thermal cis-to-trans isomerization of 4-dimethylamino-4′-nitroazobenzene(NDAAB) derivatives have been studied. 2-Methyl- and 2′-chloro–NDAAB isomerize faster than NDAAB, and 2′-methyl- and 2-chloro-NDAAB isomerize slower than NDAAB. For 2,2′-dimethyl- and 2,2′-dichloro-NDAAB, the rates are between those of the monosubstituted ones. These findings are very similar to those for 4-(dimethylamino)azobenzene (DAAB) derivatives, and no fundamental difference in the kinetic-substituent effects was observed between NDAAB and DAAB. The volume of activation, which is of a negative value, varies remarkably from solvent to solvent and from substituent to substituent; its magnitude increases generally with an increase in the solvent polarity. Even for DAAB and 4,4′-bis(diethylamino)azobenzene (BDEAAB), the rate is appreciably accelerated by external pressures in polar solvents. It is concluded that the observed results are more consistent with the inver...

Solid-state fluorescent photophysics of some 2-substituted benzothiazoles

Abstract: The solid-state fluorescence properties of a series of benzothiazoles with phenyl, naphthalene, and coumarin moieties substituted at the 2-position have been investigated. The necessity for a 2′-OH substituent for fluorescence has been confirmed and the effects of further substitution in the 2-phenyl ring are reported.

Substituent effects on benzyl radical hyperfine coupling constants. Part 2. The effect of sulphur substituents

Abstract: Several 4-substituted benzyl radicals of the general form R(On)SC6H4CH2•(n = 0, 1, 2; R = Me, Ph, Tol, COCH3 OCH3) have been investigated by electron spin resonance (esr) spectroscopy. In general, ...

Polymerization of 3-methyl-2,5-dibromothiophene utilizing n-butyl lithium and copper(II) chloride

Abstract: : In recent years, there have been extensive research activities focussed on macromolecules with extended pi-electron system. Among the many macromolecules studied, conjugated olefinic compounds (polyenes), have been given much attention. Various methods for their synthesis have been reported. In the heterocyclic category, there are four reports on the synthesis of poly(3-substituted-2,5-thienylene) (substituent = H, CH3) via coupling of 3-substituted-2,5-dibromothienylmagnesium by nickel salt promoters. Recently Afanas'ev, et al. reported also about the preparation of poly(2,5-thienylene) by an electrochemical method. The ability for charge transport through the thiophene polymer chain is an important criterion for achieving high conductivity. For that reason the synthesis of polyenes was studied. The present investigation was undertaken to improve the synthesis of poly(3-methyl-2,5-thienylene) and to obtain a magnesium free material. n-Butyl lithium was used as dehaloginating agent. Cu(II) chloride was utilized to serve as catalyst.

Organic counterions and micellar parameters: substituent effects in a series of benzoates

Abstract: Determination des concentrations critiques micellaires obtenues par la methode de tension de surface pour des micelles de decyltrimethylammonium dans des solutions 0,5000 M de 20 ions antagonistes aromatiques sous forme de sels de sodium

Benzonorbornenyl, benzopyranyl and benzothiopyranyl retinoic acid analogues

Abstract: Compounds of the formulas (I), (II) and (III), where R1, R2, R3 and R4 are hydrogen or methyl, X is hydrogen or fluorine and Q is formula (IV), (V), (VI), (VII), (VIII), or (IX), and X1 is hydrogen, hydroxy, methoxy or fluorine, R is hydroxy, alkoxy with 0 or 1 hydroxy substituent, aroxy or NR5R6, where R5 is hydrogen, alkyl with 0 or 1 hydroxy substituent or aryl, and R6 is alkyl with 0 or 1 hydroxy substituent or aryl, with the provisos that X is fluorine only when R2 is methyl, when R3 or R4 is methyl the other R3 or R4 is also methyl and when Q is said thienyl group Q may be in either the cis or trans position. These compounds are useful as chemopreventive agents for inhibiting tumor promotion in epithelial cells and for treating nonmalignant skin disorders.

Imidazolylphenyl)formamidines. A structurally novel class of potent histamine H2 receptor antagonists.

Abstract: Structure-activity considerations of N alpha-guanylhistamine, the first compound found with detectable H2-antagonist activity, led to the synthesis of a series of conformationally rigid guanylhistamine analogues, namely, (imidazolylphenyl)guanidines, imidazolylbenzamidines, and (imidazolylphenyl)formamidines. It was found that in the guanidine and benzamidine classes, the meta-substituted derivatives (3, 4, 7, and 8) possessed H2-antagonist activity, whereas in the class of formamidines, only the para-substituted derivative 10 was found active. A subsequent increase in the size of the substituent at the formamidino group of 10 led to compounds (15-20) of high H2-antagonist affinity, which was related to the gastric antisecretory effect. Members of this structurally novel class of H2 antagonists were 20- to 50-fold more potent than cimetidine both "in vitro" and "in vivo". Structure-activity relationships are discussed in terms of ionization properties, partitioning behavior, conformational aspects of the selected compound 17, and of possible modes of interaction with the histamine H2 receptor. It was found that the formamidine moiety was an important structural feature and that H2-antagonist activity requires correct steric and electronic properties. Compound 17 (DA 4577), owing to its pharmacological profile and demonstrated safety in animals, was selected to be clinically investigated.

Carbohydrate radicals: from ethylene glycol to DNA strand breakage.

Abstract: Radiation-induced DNA strand breakage results from the reactions of radicals formed at the sugar moiety of DNA. In order to elucidate the mechanism of this reaction investigations were first performed on low molecular weight model systems. Results from studies on deoxygenated aqueous solutions of ethylene glycol, 2-deoxy-D-ribose and other carbohydrates and, more relevantly, of D-ribose-5-phosphate have shown that substituents can be eliminated from the beta-position of the radical site either proton and base-assisted (as in the case of the OH substituent), or spontaneously (as in the case of the phosphate substituent). In DNA the C(4') radical undergoes strand breakage via this type of reaction. In the presence of oxygen the carbon-centred radicals are rapidly converted into the corresponding peroxyl radicals. Again, low molecular weights models have been investigated to elucidate the key reactions. A typical reaction of DNA peroxyl radicals is the fragmentation of the C(4')-C(5') bond, a reaction not observed in the absence of oxygen. Although OH radicals may be the important direct precursors of the sugar radicals of DNA, results obtained with poly(U) indicate that base radicals may well be of even greater importance. The base radicals, formed by addition of the water radicals (H and OH) to the bases would in their turn attack the sugar moiety to produce sugar radicals which then give rise to strand breakage and base release. For a better understanding of strand break formation it is therefore necessary to investigate in more detail the reactions of the base radicals. For a start, the radiolysis of uracil in oxygenated solutions has been reinvestigated, and it has been shown that the major peroxyl radical in this system undergoes base-catalysed elimination of O2-., a reaction that involves the proton at N(1). In the nucleic acids the pyrimidines are bound at N(1) to the sugar moiety and this type of reaction can no longer occur. Therefore, with respect to the nucleic acids, pyrimidines are good models only in acid solutions where the O2-. elimination reaction is too slow to compete with the bimolecular reactions of the peroxyl radicals. Moreover, the long lifetime of the radical sites on the nucleic acid strand may allow reactions to occur which are kinetically of first order, and which cannot be studied in model systems at ordinary dose rates. It is therefore suggested to extend model system studies to low dose rates and to oligonucleotides. Such studies might eventually reveal the key reactions in radical-induced DNA degradation.

3-Substituent effect and 3-methylene substituent effect on the structure-reactivity relationship of 7 beta-(acylamino)-3-cephem-4-carboxylic acid derivatives studied by carbon-13 and IR spectroscopies.

Abstract: Relationships between the chemical reactivity of 3-substituted cephalosporins or 3-methylene-substituted cephalosporins and several parameters observed by 13C NMR and IR spectroscopies are described. Among 3-substituted cephalosporins, the values of delta (C-3) and delta (COO) of 13C NMR spectra are correlated with the logarithms of the rate constants for alkaline hydrolysis (log kobsd) when substituents at the 3-position are classified into two groups, i.e., OR substituents and others. Among the 3-methylene-substituted cephalosporins, the difference values of the 13C chemical shifts for C-3 and C-4, delta delta (4-3), are correlated with log kobsd. The beta-lactam vC = O value of the solution IR spectra is a good index for the prediction of a significant change of the beta-lactam reactivity resulting from modification of a 3-substituent or a 3-methylene substituent. From analysis of these observed parameters, both resonance and inductive effects of the substituent at the 3-position were found to affect the chemical reactivity of the beta-lactam ring in cephalosporin, while only the inductive effect of the substituent at the 3'-position was found to affect the beta-lactam reactivity.

Pyridonecarboxylic acids as antibacterial agents. 4. Synthesis and antibacterial activity of 7-(3-amino-1-pyrrolidinyl)-1-ethyl-6-fluoro-1,4 -dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid and its analogues.

Abstract: The title compounds (28-56) with an amino- and/or hydroxy-substituted cyclic amino group at C-7 were prepared with 1-substituted 7-chloro-, 7-(ethylsulfonyl)-, and 7-(tosyloxy)-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3- carboxylic acids and their ethyl esters (3-7) with cyclic amines such as 3-aminopyrrolidine. The N-1 substituent includes ethyl, vinyl, and 2-fluoroethyl groups. As a result of in vitro and in vivo antibacterial screenings, three compounds, 1-ethyl- and 1-vinyl-7-(3-amino-1-pyrrolidinyl)-6-fluoro- 1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids (33a and 33b) and 1-vinyl-7-[3-(methylamino)-1-pyrrolidinyl] analogue 34b, were found to be more active than enoxacin (2) and to be worthy of further biological study. Structure-activity relationships are discussed.

Positional selectivity of the methylation of 5-substituted tetrazolate anions

Abstract: The methylation of a series of 15 sodium 5-substituted tetrazolates using iodomethane in acetone/water (4 : 1) has been studied. The reaction yields both 1- and 2-methyl products, and the ratio of these products is discussed in terms of the nature of the 5-substituent. Electronic and steric effects dominate the reaction pathway; both increased substituent electro negativity and steric bulk lead to predominant methylation at N2. Sodium 5-ethoxycarbonyltetrazolate (3n) goes against this trend and an intermediate is proposed where the incoming electrophile is associated with the ester carbonyl group.

Organosilicon compounds and preparation and use thereof

Abstract: Organosilicon compounds which are silanes or siloxanes characterized by the presence of silicon-bonded groups represented by the general formula ##STR1## in which R' is a divalent hydrocarbon group which may contain ether oxygen, R" represents --CHBCH 2 -- or --C 6 H 9 B-- in which B is OH or the group ##STR2## a and n are each 0 or 1 and Y is --OH, lower alkoxy or --NX 2 wherein X represents hydrogen or lower alkyl. The compounds are prepared by the reaction of an organosilicon compound having an organic substituent which contains an epoxy group, and the appropriate acid or acid chloride. They absorb ultra violet radiation and are useful as cosmetic and other sunscreen agents.

Thermoplastic resin composition

Abstract: PURPOSE:A composition obtained by blending a thermoplastic resin with a specific fluorine-contained polymer, showing improved lubricating effect with a small amount of it, having improved molding properties, providing molded articles having good appearance CONSTITUTION:100ptswt thermoplastic resin is blended with 0001-1ptwt, preferably 0005-07ptwt fluorine-contained polymer having a -SO3M group (M is alkali metal) A single polymer of a fluorine-contained vinyl compound shown by the formula (l and m are 0-4; n is 0 or 1; p is 0-12; R and R are F, or H; X is F, Cl, or CF3; X is F or CF3; Y is X ; Y is F or 1-10C perfluoroalkyl; M is alkali metal) or a copolymer of the compound and a fluorinated alpha-olefin compound shown by the formula FR =CR R (R is H or F; R and R are F, Cl, H, or CF3), fluorodivinyl compound, etc is used as the fluorine-contained polymer, and especially a polymer whose substituent groups are all F is preferable

Method of inhibiting sweetness

Abstract: The sweetness of an ingestible product containing a sweetening sugar or sugar alcohol in large quantities can be reduced by incorporating therein a sweetness-reducing amount of at least one compound of the general formula: ##STR1## in which m represents 0 or 1, and when m represents 0, n represents 1, 2 or 3, and p represents 1, 2, 3 or 4, and when m represents 1, n represents 1 or 2 and p represents 0, 1, 2, 3 or 4; the substituents R, which may be the same or different, each represent a lower alkoxy group, e.g. with 1 to 5 carbon atoms, phenoxy group or a lower alkyl or trifluoromethyl group; and/or two substituents R together represent an aliphatic chain linked to the phenyl ring at two positions, either directly or via an oxa-group, e.g. an alkylenedioxy, alkenylenedioxy, alkylenoxy or alkenylenoxy group; and/or one substituent R represents a hydroxy group while at least one other substituent R represents an alkoxy group; and X + represents a physiologically acceptable cation.

Toner for developing electrostatic charge image

Abstract: A toner for developing electrostatic latent images, comprises: 100 parts by weight of a binder resin; 20 to 200 parts by weight of magnetic powder; and 0.01 to 10 parts by weight of a compound represented by the following formula ##STR1## wherein A is a phenylene group, which may have a substituent selected from a nitro group, a halogen atom, an alkoxy group having 1 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an aralkyl group having 7 to 18 carbon atoms or an aryl group having 6 to 18 carbon atoms; B is a phenylene group or a naphthylene group which may have a substituent selected from a nitro group, a halogen atom, a carboxyl group, an anilide group, an alkoxy group having 1 to 18 carbon atoms, a carboxyester group having 2 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an aralkyl group having 7 to 18 carbon atoms or an aryl group having 6 to 18 carbon atoms; X and Y each are --O--, --COO--, --S-- or ##STR2## where R is hydrogen or an alkyl having 1 to 4 carbon atoms; M represents scandium, vanadium, manganese or zinc; C represents hydrogen, sodium, potassium, ammonium or organic ammonium; with the proviso that when A or B has plural substituents, they may be either the same or different.