Showing papers on "Substituent published in 1978"

Some reactions of meso-formyloctaethylporhyrin

Abstract: Grignard reactions on nickel meso-formyloctaethylporphyrin (1a) yield methyl and phenyl carbinols. The former is readily dehydrated to the meso-vinyl derivative, which by hydrogenation yields the meso-ethyl analogue, and by bromination and dehydrobromination affords the meso-ethynyl compound. The latter is readily oxidised to the 1,4-diporphyrinylbuta-1,3-diyne. Reaction of sulphuric acid with the meso-phenyl carbinol gives a meso-benzyl derivative in which one β-ethyl group has been dehydrogenated to give a β-vinyl substituent. Attempts to form a carbene from (1a) with triethyl phosphite gave the meso-propenyl compound and with boron trifluoride and zinc amalgam gave the meso-formyloxy derivative, which is transformed readily into the meso-methoxy compound. Mechanisms for these novel reactions are suggested.

New applications of palladium in organic syntheses

Abstract: The palladium catalyzed vinylic substitution reaction with organic halides is a new and useful method for producing carbon-carbon bonds. The reaction is useful with aryl, heterocyclic, benzylic, and vinylic bromides and iodides. The most useful reactions are with bromides in which cases a triarylphosphine is required with the palladium catalyst. The best phosphine to employ for a specific synthesis can now be predicted based upon knowledge of how the phosphines influence vinylic substitution rates and side reactions forming phosphonium salts and palladium metal. Essentially all common functional groups can be tolerated by the reaction under the same conditions with the exception of α,β-unsaturated ketones and aldehydes. These react normally in the form of their acetals or ketals, however. Reactions proceed well with conjugated or isolated double bonds with mono-, di- and often tri-substituted olefins, generally in a stereospecific manner. A syn addition of the organopalladium compound to the olefin followed by a syn elimination of the palladium hydride is observed. The direction of addition of the organopalladium complex to the olefin depends upon the substituents present. Both steric and electronic influences have been observed. The direction of addition is dominated by steric effects; the organic group always adds, at least mainly, to the least substituted carbon of the double bond. Electron withdrawing substituents on the double bond generally cause exclusive addition of the organic group to the olefinic carbon not having the substituent. With electron donating groups, some addition to the carbon carrying the substituent is usually observed.

2-Halomethyl-5-vinyl-1,3,4-oxadiazole compounds

Abstract: Compounds represented by the following general formula: ##STR1## wherein W represents a phenyl group, a phenyl group substituted with a member selected from the group consisting of a halogen atom, a nitro group, a cyano group, an alkyl group containing 1 to 3 carbon atoms and an alkoxy group containing 1 to 4 carbon atoms, with the number of the substituents being 1 or 2 when said substituent is a halogen atom and 1 when said substituent is other than halogen, or an unsubstituted naphthyl group, and said phenyl group may take the form of ##STR2## X represents a hydrogen atom, an unsubstituted phenyl group or an alkyl group containing 1 to 3 carbon atoms, Y represents a halogen atom, and n represents an integer of 1 to 3 These compounds are useful as photo-initiators

1,4-Dihydro-quinoline-3-carboxylic acid derivatives, process for their preparation and compositions containing them

Abstract: New 7-dialkylamino-1-substituted-6-halogeno-4-oxo-1,4-dihydroquinoline-3 carboxylic acids of the formula: ##STR1## wherein the R 1 substituent is methyl, ethyl, vinyl or allyl and non-toxic pharmaceutically acceptable acid addition salts thereof. These compounds are useful as antibacterial agents. Also disclosed are processes for preparing the compounds.

Inductive, Hyperconjugative and Frangomeric Effects in the Solvolysis of 1‐Substituted 3‐Bromoadamantanes. Polar effects IV

Abstract: Three kinds of polar substitutent effects are observable in the solvolyses of 1-R-substituted 3-bromoadamantanes (VI). This follows from the relationship between products, rate constants k in 80% ethanol, and the inductive substituent constants σ of the substituent R. Alkyl groups and electron-attracting substituents at C (1) control the rate by their inductive effects alone, since logk correlates closely with σ. However, rates are higher than predicted on the basis of the respective σ values when conjugating (+ M)-substituents or electrofugal groups are attached to C(1). These exalted substituent effects are attributed to CC-hyperconjugative relay of positive charge from the cationic center at C(3) to the substituent at C(1). When the substituent is a strong electron donor (e.g. O− and S−), accelerated substitution gives way to heterolytic fragmentation, rates and products then being controlled by the frangomeric effect.

Preparation of Liquid Crystal Intermediates: 4-Substituted Alkoxybenzenes

Abstract: Improvements in the O-alkylation of 4-substituted phenols with alkyl bromides in the presence of base by using anhydrous conditions has led to better methods for the preparation of 4-substituted alkoxybenzenes in which the substituent is either an aldehyde or a protected functional group. The protected groups can be benzyloxy, acetamido and carboxylic acid methyl ester which are easily converted to hydroxy, amino and acid chloride groups. A mixture of N,N-dimethylformamide and benzene containing molecular sieves and sodium hydroxide as the base along with an azeotropic distillation provides the necessary anhydrous conditions to avoid hydrolysis of the protecting groups. A variety of mesomorphic compounds such as 4,4′-disubstituted phenylbenzoates, phenylthiobenzoates, benzylideneamino (Schiff's bases) compounds and azoxybenzenes in which at least one of the terminal substituents is an alkoxy group can be prepared from these 4-substituted alkoxybenzenes.

Radikalionen, XIX: Einelektronen‐Oxidationen (H3C)3SiCH2‐substituierter Benzole in der Gasphase und in Lösung

Abstract: Trimethylsilylmethyl-Gruppen stabilisieren als Donatorsubstituenten insbesondere Radikalkationen Dies verdeutlichen die teils ungewohnlich niedrigen 1 und 2 Ionisierungsenergien (H3C)3SiCH2-substituierter Benzole, die sich mit einem erweiterten Storungsmodell parametrisieren und mit den 1 und 2 Charge-Transfer-Anregungsenergien ihrer TCNE-Komplexe korrelieren lassen Geeignet substituierte Benzolderivate, deren 1 Ionisierungsenergie 78 eV unterschreitet, konnen mit AlCl3 in H2CCl2 selektiv oxidiert werden Hochaufgeloste ESR-Spektren belegen Spindelokalisation und liefern — zusammen mit PE- und CT-Spektren — zusatzlich Informationen uber die Vorzugskonformation sowie uber die Beweglichkeit der Substituentengruppen in den sterisch uberfullten Benzol-Radikalkationen Radical Ions, XIX: One-Electron Oxidations of (H3C)3SiCH2-Substituted Benzenes in the Gaseous Phase and in Solution Trimethylsilylmethyl groups are donor substituents capable of stabilizing especially radical cations This is illustrated by the partly unusually low 1 und 2 ionization energies of (H3C)3SiCH2-substituted benzene derivatives, which can be parametrized within an extended perturbation model and correlated with the 1 and 2 charge transfer excitation energies of their TCNE complexes Suitably substituted benzene derivatives with first ionization potentials below 78 eV can be oxidized selectively with AlCl3 in H2CCl2 High-resolution ESR spectra confirm spin delocalization and — together with PE and CT spectra — yield additional information on the preferred conformation and on the mobility of the substituent groups in the sterically overcrowded benzene radical cation

Heterocyclic free radicals. Part 8. The influence of the structure and the conformation of the side-chain on the properties of phenothiazine cation-radicals substituted at nitrogen

Abstract: In 10-substituted phenothiazine cation-radicals the extent of variation in nitrogen hyperfine splitting is greatest for purely hydrocarbon substituents and is reduced on introduction of polar functions into the alkyl group. It is concluded that the substituent effect is mainly a through-bond inductive effect of the classical kind. Substituents greater than methyl show strong preferences for particular conformations about the N–C bond. Variations in the ratio a(N) : a(3-H) are interpreted in terms of changes in the fold angle of the radicals occurring in response to changes of substituent type. Chiral substituents, as found in certain phenothiazine drugs, have characteristic effects on the e.s.r. spectra of the derived cation-radicals: two non-equivalent proton splittings arise from the β-CH2 group.

Substituent and Medium Effects on Nitrogen-15 Shieldings of Compounds with >C=N Bonds (Imines, Oximes, and Phenylhydrazones)

Abstract: The ^(15)N chemical shifts of ^(13)N -(arylmethylidene)alkanamines, seven N-(arylmethylidene)azanols, five 1-(aryImethylidene)- 2-phenyldiazanes, and 11 N-(arylmethylidene)arenamines have been determined at the natural abundance level of ^(15)N in several solvents. The shifts of several of the N-(phenylmethylidene)alkanamines with different alkane groups have been analyzed in terms of α-,β- and y-methyl substituent effects. For those N-(arylmethylidene) azanes substituted at the para position, linear correlations with Hammett σ parameters having negative slopes are found for the ^(15)N chemical shifts. However, the ^(15)N shifts of N-(phenylmethylidene)arenamines (substituted at the para position of the arenamine moiety) are essentially insensitive to the nature of the substituent. The slopes of the Hammett correlations become more negative with increasing proton-donating power of the solvent for most series of compounds studied. In general, the ^(15)N shifts were found to be 5-12 ppm toward higher fields in methanol compared to chloroform, and except for the alkylidenazanols (oximes), about the same in dimethyl sulfoxide as in chloroform. In contrast, the alkylidenazanol resonances move 13-16 ppm downfield for the change from chloroform to dimethyl sulfoxide.

Substituent and steric effects in the oxidation of alkyl aryl sulfides by peroxydisulfate

Abstract: The kinetics of oxidation of a number of alkyl aryl sulfides with potassium peroxydisulfate in aqueous ethanol have been investigated. The effect of substituents on the oxidation has been studied by employing a number of p- and m-substituted phenyl methyl sulfides: the reaction is accelerated by electron-releasing and retarded by electron-withdrawing substituents, indicating a rate-determining electrophilic attack by the peroxydisulfate ion at the reaction site, sulfur. A good correlation is found to exist between the rate constants and the Hammett σ+/σ− constants, the ρ+ value for the reaction being −0.56 with a correlation coefficient of 0.979. The activation parameters have also been determined.Studies with different alkyl phenyl sulfides clearly indicate that the reaction is quite sensitive to steric congestion around the reaction site. The results obtained in this study are compared with those found for the oxidation of the same set of sulfides with different oxidants.

Surfactants for producing low interfacial tensions: II. Linear alkylbenzenesulfonates with additional alkyl substituents

Abstract: The synthesis and low interfacial tension behavior of a variety of di- and trialkylbenzenesulfonates are described. The benzene ring carries one major alkyl substituent, consisting of a linear chain eight to sixteen carbon atoms long, and one or two additional methyl, ethyl, propyl, i-propyl, butyl, or t-butyl groups. The addition of these extra groups causes the low interfacial tensions to shift to higher molecular weight alkanes when compared to the parent linear alkylbenzenesulfonate. Surfactants in these structural classes can give very low interfacial tensions against those alkanes which best model the behavior of crude oils, but this is influenced by the number and type of the short alkyl substituents. These surfactant structures are more attractive from the point of view of tertiary oil recovery than linear alkylbenzenesulfonates.

The effect of substituents at a coordinated center on the strength of P → Sn donor-acceptor bond

Abstract: 1. The thermodynamic parameters for the complexing of SnCl4 and organotin chlorides with organophosphorus donors satisfy the general linear ΔH° vs ΔS° relation applying to donor-acceptor complexes. 2. The energy of the P → Sn bond in the (C2H5)nSnCl4−n · (C4H9)3P complexes falls off as the number of Cl atoms in the acceptor molecule is reduced. 3. The energy of the P → Sn bond in the SnCl4 · R1R2R3P complexes, and of the O → Sn bond in the SnCl4 · R1R2R3PO complexes, are closely dependent on inductive and resonance effects from the substituents R1, R2, and R3. The sensitivity of the coordination centers to substituent effects is higher in the phosphines than in the phosphine oxides.

The carbon‐13 nuclear magnetic resonance spectra of anthraquinone, eight polyhydroxyanthraquinones and eight polymethoxyanthraquinones

Abstract: The 13C NMR spectra of anthraquinone, eight hydroxyanthraquinones and eight methoxyanthraquinones are reported. Peak assignment for the carbon atoms of these compounds is achieved by using decoupling techniques and by intercomparison of the variously-substituted derivatives. Carbonyl chemical shifts in the hydroxyanthraquinones can be rationalized in terms of cross conjugation and intramolecular hydrogen bonding and in terms of cross conjugation in the methoxyanthraquinones. Hydroxy and methoxy substituent chemical shifts are also reported.