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Showing papers on "Substituent published in 1990"


Patent
14 Aug 1990
TL;DR: In this article, the authors proposed to increase an effect to activate interfaces by incorporating a sulfated oligosaccharide deriv. which is useful as a vehicle when emulsion layers or auxiliary layers are formed on various kinds of supporting bodies.
Abstract: PURPOSE: To increase an effect to activate interfaces by incorporating a sulfated oligosaccharide deriv. which is useful as a vehicle when emulsion layers or auxiliary layers are formed on various kinds of supporting bodies. CONSTITUTION: This silver halide photographic sensitive material contains a glycoside of sulfated oligosaccharide expressed by (sugar A)-Q-(sugar)n -Q-(sugar B)-QR or its salt in which >=20% of hydroxyl groups in the sugar part is sulfated with sulfuric acid. In formula, (sugar A) and (sugar B) are same or different monosaccharides. (sugar)n represents a sugar chain with n= 0 to 30 of single monosaccharide or plural kinds of monosaccharides.-Qbetween the monosaccharides is a glycoside bond which represents an ether bond between the first position as the molecular end of the one sugar and a hydroxyl group except for the first position of the other sugar. -QR is a substituent which is bonded with the first position of the molecular end of reduced oligosaccharide. R is C1-C30 alkyl group, alkylene group or alkynyl group which may be substituted or C6-C40 aryl group or heterocyclic group which may be substituted.

790 citations


Book
01 Jan 1990
TL;DR: The Mechanism of Electrophilic Aromatic Substitution as discussed by the authors replaces a Substituent X by a substitute Y by the replacement of X by Y. Quantitative Evaluation of Electronic and Steric Effects in EAS Substitution.
Abstract: The Mechanism of Electrophilic Aromatic Substitution. Hydrogen Exchange. The Replacement of a Substituent by Hydrogen. Metallation. Reactions Involving Electrophilic Carbon. Reactions Involving Nitrogen Electrophiles. Oxygen, Sulphur, and Selenium Electrophiles. Electrophilic Halogenation. The Replacement of a Substituent X by a Substituent Y. Quantitative Evaluation of Electronic and Steric Effects in Electrophilic Aromatic Substitution.

403 citations


Patent
01 Oct 1990
TL;DR: Sulfonium, selenonium and phosphonium salts, useful as photoinitiators, include: a chromophore which absorbs visible radiation, a removable positive hydrogen ion and exhibiting a higher energy occupied molecular orbital than at least one other substituent attached to the S, Se, As, N or P atom of the salt.
Abstract: Sulfonium, selenonium, arsonium, ammonium and phosphonium salts, useful as photoinitiators, comprise: a chromophore which absorbs visible radiation, the chromophore (1) having a removable positive hydrogen ion and (2) exhibiting a higher energy occupied molecular orbital than at least one other substituent attached to the S, Se, As, N or P atom of the salt; a group which links the chromophore to the S, Se, As, N or P atom of the salt, the group partially preventing π resonance between the chromophore and the other substituents in the salt; at least one substituent comprising an electron withdrawing group and exhibiting a lower unoccupied molecular orbital than the chromophore; and, an anion; the salts being capable, upon exposure to visible radiation, of forming a Bronsted acid.

263 citations


Journal ArticleDOI
Otto J. Scherer1
TL;DR: In this article, the phosphorus, arsenic, antimony and bismuth ligands were nearly always understood to be molecules such as R3E, R2E(CH2)nER2, and RC[(CH 2 nER2]3(E = P, As, Sb, Bi) in which the lone pair of the atom E functions as a 2e donor.
Abstract: Until recently, phosphorus, arsenic, antimony and bismuth ligands were nearly always understood to be molecules such as R3E, R2E(CH2)nER2, and RC[(CH2)nER2]3(E = P, As, Sb, Bi) in which the lone pair of the atom E functions as a 2e donor. Current research interests, however, increasingly involve substituent-free En ligands (n = 1–6), the various types of which are mainly accessible via EX3 (X = F,Cl,Br,Ph), E (SiMe3)3, (RAs)n, P4S3, As4S4, gray arsenic, and especially P4 and As4; these ligands can be stabilized in the coordination spheres of certain transition metal fragments. P1, As1 and Sb1 units with multiple M-E bonds are found in bi- and trinuclear complexes; E1 units can also be encapsulated (partially or completely) in cavities of a variety of metal cluster frameworks. Metallatetrahedranes with up to three E atoms are especially common. Besides E1 units, the greatest variety of coordination modes is exhibited by E4 ligands, which are found as intact tetrahedra and also as parts of chains, polycycles, cubes and a trigonal prism. The phosphorus and arsenic species cyclo-En, isoelectronic to the carbocyclic (CH)n species, are suitable ligands for forming sandwich complexes (n =3, 4, 5) and triple-decker sandwich complexes (n = 3, 5, 6). In addition to the wide variety of chemical reactions, remarkable parallels are found in organic chemistry as well as in solid-state chemistry for many of these substance classes. Some of the molecules have received lively interest from theoretical chemists.

233 citations


Journal ArticleDOI
Abstract: A number of substituted 1,8-naphthalimides and naphthalic anhydrides have been prepared and their absorption and fluorescence properties in absolute ethanol have been determined. In the absence of an alkylamino substituent in the naphthalene ring, the compounds are colourless and weakly fluorescent. In the presence of such a substituent they become yellow and frequently fluoresce strongly with quantum yields of the order of 0.8.

210 citations


Journal ArticleDOI
TL;DR: The complete synthesis of chlorophyll a starting from Knorr's pyrrole was described in detail in this article, with full experimental detail, in which the four pyrroles which are required for rings A, B, C and D were elaborated largely by known reactions, although with considerable improvements.

172 citations



Journal ArticleDOI
TL;DR: In this paper, the electrochemical oxidation and reduction potentials of substituted benzyl, cumyl, and diphenylmethyl radicals are found to give linear correlations with σ + and σ −.
Abstract: The electrochemical oxidation and reduction potentials of substituted benzyl, cumyl, and diphenylmethyl radicals are found to give linear correlations with σ + and σ − . Although the redox potentials reflect the thermochemical properties of both the radicals and the product ions substituent effects on the ion dominate leading to a simple relationship between the oxidation potential and pK R + and the reduction potential and pK a (R−H)

105 citations


Patent
25 Apr 1990
TL;DR: A compound of the formula as discussed by the authors can have suitable sub-substituent(s) or pyridyl(lower)alkyl which may have suitable substrate(s).
Abstract: A compound of the formula : wherein R¹ is lower alkyl, aryl, arylamino, pyridyl, pyrrolyl, pyrazolopyridyl, quinolyl, or a group of the formula : wherein the symbol of a line and dotted line is a single bond or a double bond, X is CH or N, and Z is O, S or NH, each of which may have suitable substituent(s); R² is hydrogen or lower alkyl; R³ is hydrogen or hydroxy; R⁴ is lower alkyl which may have suitable substituent(s), and R⁵ is ar(lower)alkyl which may have suitable substituent(s) or pyridyl(lower)alkyl, or R⁴ and R⁵ are linked together to form benzene-condensed lower alkylene; A is an amino acid residue excepting D-Trp, which may have suitable substituent(s); and Y is bond, lower alkylene or lower alkenylene, and a pharmaceutically acceptable salt thereof, processes for their preparation and pharmaceutical compositions comprising them as active ingredient in association with a pharmaceutically acceptable carrier or excipient.

97 citations


Patent
12 Sep 1990
TL;DR: A monocyclopentadienyl or substituted cyclopentadiyl metal complex containing compound useful as an addition polymerization catalyst corresponds to the formula: CpMXn⁺A⁻ where n is 1 or 2 depending on the valence of M; n is a noncoordinating compatible anion of a Bronsted acid salt.
Abstract: A monocyclopentadienyl or substituted monocyclopentadienyl metal complex containing compound useful as an addition polymerization catalyst corresponds to the formula: CpMXn⁺A⁻ wherein: Cp is a single η⁵-cyclopentadienyl or η⁵-­substituted cyclopentadienyl group optionally covalently bonded to M through a substituent; M is a metal of Group 3-10 or the Lanthanide Series of the Periodic Table bound in an η⁵ bonding mode to the cyclopentadienyl or substituted cyclopentadienyl group; X each occurrence is hydride or a moiety selected from halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide, siloxy,and combinations thereof having up to 20 non-hydrogen atoms, neutral Lewis base ligands having up to 20 non-hydrogen atoms; or optionally one X together with Cp forms a metallocycle of up to 20 non-­hydrogen atoms with M; n is 1 or 2 depending on the valence of M; and A⁻ is a noncoordinating, compatible anion of a Bronsted acid salt.

87 citations


Journal ArticleDOI
TL;DR: In this paper, a unified explanation of deformation and substituent effects for group IV double bonds is given, which is correlated with ab initio calculations on electron withdrawal by substituents to determine the factors that govern geometry and bonding.
Abstract: A unified explanation of deformation and substituent effects is given for group IV double bonds. Results from experiments and previous theoretical work are correlated with ab initio calculations on electron withdrawal by substituents to determine the factors that govern geometry and bonding. Predictions are made and calculations carried out for a silyl substituent as a test of our hypotheses. In order to systematically investigate substituent effects we have adopted a nuclear charge perturbation approach. The GAUSSIAN set of ab initio electronic structure programs has been modified so that a continuous range of electron withdrawal is available

Journal ArticleDOI
TL;DR: A series of eleven 6-substituted 2-aminopurines was N-alkylated with 2-acetoxymethyl-4-iodobutyl acetate.

Journal ArticleDOI
TL;DR: In this paper, a kinetic and ab initio study of the prooxidant effect of vitamin E derivatives has been carried out and the second-order rate constant for the hydrogen abstraction dramatically increases as the number of π-electron systems activating the hydrogen (C=C double bonds) increases from zero to two.
Abstract: A kinetic and ab initio study of the prooxidant effect of vitamin E derivatives has been carried out. Rates of hydrogen abstraction from various fatty acid esters and egg yolk lecithin by tocopheroxyl radicals have been determined spectrophotometrically. The second-order rate constant for the hydrogen abstraction dramatically increases as the number of π-electron systems activating the hydrogen (C=C double bonds) increases from zero to two. The rate constants per an active hydrogen for the various fatty acid esters that contain hydrogens activated by two π-electron systems are similar to one another. In order to interpret the observed features of the rate constants, ab initio calculations of models for the fatty acid esters have been carried out. From the calculation results, it is shown that the observed features of the rate constant can be explained in terms of the pseudo-π-conjugation between the C=C double bond and the active hydrogen-carbon bond. The bulkier the substituent groups at the 5- and 7-positions of the tocopheroxyl radical, the smaller the rate constant of the hydrogen abstraction

Journal ArticleDOI
TL;DR: In this article, the eight-membered C-ring can be closed by introducing a three-carbon bridge between the isoquinuclidine nitrogen and the 3 position of the indole ring.
Abstract: The Diels-Alder adducts formed from 1-(benzyloxycarbonyl)-1,2-dihydropyridine or 1-(benzyloxycarbonyl)-4-methoxy-1,2-dihydropyridine by reaction with methyl 2-[1-(phenylsulfonyl)-1H-indol-2-yl]-1-propenoate can serve as precursors of the 5,6-homologues of the iboga alkaloid skeleton. The eight-membered C-ring can be closed by introduction of a three-carbon bridge between the isoquinuclidine nitrogen and the 3-position of the indole ring. Electrophilic cyclization proceeds in modest yield. Intramolecular Heck reactions involving a 3-iodinated indole ring and N-acryloyl or N-allyl derivatives of the isoquinuclidine ring are efficient only when the indole ring is N-methylated. Intramolecular radical addition of a 3-iodinated indole occurs when a 2-ethoxycarbonyl, 2-phenylsulfonyl, or 2-phenylsulfinyl substituent is present on a N-allyl isoquinuclidine substituent. The cyclization products from the 2-phenylsulfonyl case can be converted to various homoiboga derivatives

Journal ArticleDOI
TL;DR: In this paper, it was shown that the ratio of cis to trans structural units obtained by isomerization prior to double bond formation dictates the degree of backbiting and intramolecular cyclization reactions.
Abstract: The polymerization of phenylacetylene initiated by MoCl5 and WCl6 based initiators was monitored directly in the NMR sample tube and demonstrated the presence of backbiting and intramolecular cyclization reactions. It was shown that the ratio of cis to trans structural units obtained by isomerization prior to double bond formation dictates the degree of backbiting and intramolecular cyclization reactions. This cis–trans ratio determines the length of cis–transoidal sequences present in the polymer backbone which are available for both backbiting and intrachain cyclization reactions. The cyclic trimers obtained in the metathesis polymerization of phenylacetylene are formed only through the cis–cisoidal-induced backbiting and/or intramolecular reactions. The o-trimethylsilylphenylacetylene follows a living mechanism of polymerization. This is due to the fact that the size of the ortho substituent suppresses the cis–transoidal to cis–cisoidal isomerization reactions and therefore eliminates the backbiting reactions. The steric hindrance provided by the size of the ortho substituent also eliminates interchain and intrachain reactions.

Journal ArticleDOI
TL;DR: In this paper, the regioselectivity of palladium-catalyzed arylation reactions of a series of nitrogen-containing vinyl ethers was reported, and the presence of a β-amino substituent gave a profound influence on regiochemistry.
Abstract: The regioselectivity of palladium-catalyzed arylation reactions of a series of nitrogen-containing vinyl ethers is reported. The presence of a β-amino substituent gives a profound influence on regiochemistry. Thus, the arylation of [2-(dimethylamino)ethoxy]ethene (1c) with a variety of aryl iodides and bromides provides the β-arylation products [2-[2-(dimethylamino)ethoxy]ethenyl]arenes (3) with at least 95% selectivity and in good yields. The corresponding arylation of butoxyethene is a nonselective process giving a mixture of α- and β-substitution products. The palladium-catalyzed arylation of 1c constitutes an entry to 2-arylethanals after cleavage of the enol ether. The directing effect of the amino group is discussed in terms of chelation with the intermediate arylpalladium halide

Journal ArticleDOI
TL;DR: In this article, 15N NMR spectra of 8-hydroxy-2'-deoxyguanosine and its RNA analogue were analyzed with respect to their tautomeric structures.
Abstract: The favored tautomeric and ionic structures were examined for the oxidative DNA damage adduct 8-hydroxy-2'-deoxyguanosine and its RNA analogue 8-hydroxyguanosine by 15N NMR spectroscopy. In addition, 15N chemical shifts and coupling constants from 13 different guanine nucleosides, including a wide variety of C8 substitutions (OH, SH, Br, OCH2C6H5, OCH3, SCH3, and SO2CH3), have been analyzed with respect to their tautomeric structures. A -98.5-Hz proton-nitrogen coupling constant observed for the N7 resonance of 8-hydroxyguanosine in dimethyl sulfoxide was evidence for 8-keto substitution, which is contrary to the structure implied by the generally used nomenclature. The pH dependence of 15N NMR spectra of 8-hydroxyguanosine in aqueous solution showed downfield shifts of the N1 and N7 resonances that were greater than 50 ppm, which indicated the conversion from a neutral 6,8-diketo to a 6-enolate-8-keto (pKa1 = 8.6) and finally to a 6,8-dienolate structure (pKa2 = 11.7). There was no evidence of an 8-enol substituent in the absence of ionization. It is proposed that the syn conformation of these oxidized bases in duplex DNA and RNA can be further stabilized by abnormal hydrogen bonding or mispairing that involves N7-H. The combined data show that 15N NMR is a sensitive probe to examine tautomerism of the guanine ring system. The analysis indicates that the change from a single to a double bond for the C8 substituent, and the accompanying removal of the normal double bond between N7 and C8 on the imidazole ring system, has no detectable effect on the tautomerism at the N1-O6 site of the pyrimidine ring system for both the 8-keto and 8-thio substitutions. In addition, large differences in electronegativity of the C8 substituents do not alter the N1-O6 tautomerism.

Patent
05 Mar 1990
TL;DR: In this article, a compound represented by the following general formula (I): wherein R₁ and R represent a hydrogen atom, an alkyl group, an aralkyl group, a nobornylidene group, or a bicyclic aromatic fused ring which is substituted with at least one substituent selected form the group consisting of a halgoen atom.
Abstract: Disclosed is a compound represented by the following general formula(I): wherein R₁ and R₂, which may be the same or different, represent a hydrogen atom, an alkyl group, an aryl group, an aralkyl group or a substituted amino group, R₃ and R₄, which may be the same or different, represent an alkyl group, or R₃ and R₄ together form a nobornylidene group or bicyclo[3,3,1]9-nonylidene group which may have a substituent, and represents a divalent aromatic hydrocarbon group or divalent unsaturated heterocyclic group which may have a substituent, with the proviso that when R₃ and R₄ represnet an alkyl group, represents a bicyclic aromatic fused ring which is substituted with at least one substituent selected form the group consisting of a halgoen atom, an alkyl group, an alkoxy group, -R₅- S-R₆ and (in which R₅ represents an alkylene group or ( O-R₈ ) (in which R₈ represents an alkylene group and n is a positive integer), R₆ and R₇, which may be the same or different, represent an alkyl group, and X represents at least one of the substituents beign an alkyl group having 6 to 20 carbon atoms, an alkoxy group having 6 to 20 carbon atoms,

Patent
12 Dec 1990
TL;DR: A compound of forumula is a group of the formula as discussed by the authors, where R 1 is aryl, R 2 is hydroxy or lower alkoxy, R 3 is hydrogen or lower alkyl which may have suitable substituent(s), R 4 is ar(lower)alkyl, R 5 is carbonyl or sulfonyl, and Y is lower alkenylene.
Abstract: A compound of forumula: wherein R 1 is aryl, or a group of the formula : wherein X is CH or N, and Z is 0 or N-R 5 , in which R 5 is hydrogen or lower alkyl, R 2 is hydroxy or lower alkoxy, R 3 is hydrogen or lower alkyl which may have suitable substituent(s), R 4 is ar(lower)alkyl which may have suitable substituent(s), A is carbonyl or sulfonyl, and Y is bond or lower alkenylene, and pharmaceutically acceptable salt thereof, processes of their preparation and pharmaceutical compositions comprising them as an active ingredient in admixture with pharmaceutically acceptable carriers.

Patent
06 Apr 1990
TL;DR: In this article, a group of Peptide compounds having Substance P antagonism of the formula is defined, where the symbol of a line and dotted line is a single bond or a double bond; X is CH or N; Z is O, S or NH; and Y is bond, lower alkylene or lower alkenylene; their pharmaceutically acceptable salts are disclosed.
Abstract: Peptide compounds having Substance P antagonism of the formula: ##STR1## wherein R1 is lower alkyl, aryl, arylamino, pyridyl, pyrrolyl, pyrazolopyridyl, quinolyl, or a group of the formula: ##STR2## wherein the symbol of a line and dotted line is a single bond or a double bond; X is CH or N; Z is O, S or NH; R2 is hydrogen or lower alkyl; R3 is hydrogen or hydroxy; R4 is lower alkyl which may have suitable substituent(s); R5 is ar(lower)alkyl which may have suitable substituent(s) or pyridyl(lower)alkyl, or R4 and R5 are linked together to form benzene-condensed lower alkylene; A is an amino acid residue excepting D-Trp, which may have suitable substituent(s); and Y is bond, lower alkylene or lower alkenylene; and their pharmaceutically acceptable salts are disclosed.

Journal ArticleDOI
TL;DR: The results of the homogeneous asymmetric hydrogenation of several dehydroamino acids by rhodium-diene complexes of the chiral ligands are reported in this article.
Abstract: The results of the homogeneous asymmetric hydrogenation of several dehydroamino acids by rhodium-diene complexes of the chiral ligands; 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino)butane, 2a ; 2,4-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino)pentane, 3a ; and 2,3-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino) butane, 4a ; and their N-protonated and N-Me quaternized analogues are reported. The ligands comprise a versatile set which can be used both in organic and aqueous solvents. A detailed investigation of solvent and substituent effects is provided. The presence of p-NMe 2 groups enhances the rate of reaction in all cases. For the DIOP derivative, 2a , the presence of the dimethylamino group causes a reversal in the observed dominant product antipode. This is attributed predominantly to a change in preferred ligand conformation rather than to a kinetic difference between the two diastereomers of a single ligand conformation.


Journal ArticleDOI
TL;DR: An efficient procedure using free radical chemistry for introducing a carbon substituent to the 3′position of 3′-deoxythymidine is described in this article, and an application of this procedure to the synthesis of 3''-deoxy-3''-(2-propynyl)thymidine and 3''−cyanomethyl-3′−3''−deoxyntychymidine, two close analogs of AZT, is presented


Journal ArticleDOI
TL;DR: In this article, a two-step procedure consisting of an asymmetric epoxidation mediated by a poly-L-leucine polymer, followed by a previously unreported Baeyer-Villiger oxidation was found to depend on the aryl substituent.

Journal ArticleDOI
TL;DR: In this paper, the precursors with methyl, methoxy, and acetoxy substituents have been examined, and the results show that 2-tetralones are obtained directly.
Abstract: Rhodium(II) acetate-catalysed cyclisation of α-diazoketones derived from 3-arylpropionic acid produces bicyclo[5.3.0]decatrienones or 2-tetralones depending on the substitution pattern of the aryl ring in the precursor; the former products are transformed into the latter catalytically with trifluoroacetic acid. Precursors with methyl, methoxy, and acetoxy substituents have been examined, efficient cyclisation occurring in all cases. When the precursor contains a meta-methoxy substituent, 2-tetralones are obtained directly. The efficient conversion of 3-phenylpropionic acid into trans-1-methylbicyclo[5.3.0]decan-2-one is also described, partial asymmetric synthesis having been realised through the use of rhodium (S)-mandelate as the cyclisation catalyst. Cyclisations of diazoketones derived from 4-phenylbutyric acid and 5-phenylpentanoic acid have also been studied; the former provides a new entry into the bicyclo[5.4.0]undecane system whereas the latter produces a 2,3-disubstituted cyclopentanone via C–H insertion. Aspects of the cycloheptatriene-norcaradiene equilibrium in fused ring systems are discussed.


Journal ArticleDOI
TL;DR: In this paper, a photodeconjugation of α, β -unsaturated esters or lactones using catalytic amounts of new chiral cyclic inductors derived from (+) camphor is described.


Journal ArticleDOI
TL;DR: In this article, the temperature dependence of the rates of alkaline hydrolysis of five-membered cyclic phosphate and phosphonate esters has been determined, and the enthalpies of activation for the cyclic esters are much less than those for the corresponding acyclic ones.
Abstract: The hydrolysis of five-membered cyclic phosphate and phosphonate esters is about 10 6 -fold more rapid than the hydrolysis of related acyclic esters. The origin of the enhanced reactivity of the cyclic esters has been ascribed to enthalpic factors, associated with ground-state strain, and to entropic factors, associated with optimal orbital orientations. The temperature dependence of the rates of alkaline hydrolysis of ethyl and methyl esters of ethylene phosphate and of ethyl and methyl esters of propylphosphonate have been determined. The enthalpies of activation for the cyclic esters are much less than those for the corresponding acyclic esters while differences in entropies of activation are dependent on the nature of the alkyl substituent, varying from less than 1 cal mol −1 deg −1 (eu) for the methyl esters to about 8 eu for the ethyl esters