Showing papers on "Alkylation published in 1995"
TL;DR: In this paper, 2-and 4-nitrobenzenesulfonamides are obtained from primary amines and undergo smooth alkylation by Mitsunobu reaction or by conventional methods to give N-alkylated sulfonamide in near quantitative yields.
784 citations
TL;DR: The catalytic performance of zeolite β in the liquid-phase alkylation of benzene is compared with that of other solid catalysts as discussed by the authors, and a hypothesis to explain this behavior is given.
292 citations
TL;DR: In this paper, the reactions over HZSM-5 catalyst of a number of model compounds were studied in a fixed-bed micro-reactor operating at 3.6 WHSV, atmospheric pressure and temperature range 330-410°C.
Abstract: The reactions over HZSM-5 catalyst of a number of model compounds were studied in a fixed-bed micro-reactor operating at 3.6 WHSV, atmospheric pressure and temperature range 330–410°C. The compounds were propanoic acid, methyl ester of acetic acid, 4-methylcyclohexanol, cyclopentanone, 2-methylcyclopentanone, methoxybenzene, ethoxybenzene, phenol and 2-methoxy-4-(2-propenyl)phenol. These compounds represented the acid, ester, alcohol, aldehyde and ketone, ether and phenol chemical groups, which were identified as the main components of a bio-oil obtained by the high pressure liquefaction (HPL) of aspen poplar wood. Also, the reactions of a synthetically prepared volatile feed and bio-oil volatiles over HZSM-5 catalyst were investigated. The objective was to understand and identify the reaction steps involved in the HZSM-5 conversion of the bio-oil. The intent was to obtain a reaction pathway which could be used for modeling the conversion of the bio-oil. Based on the results, two reaction pathways were proposed. It was observed that the conversion of the bio-oil was complex and involved a number of reactions. These reactions could be categorized as: 1. 1. Primary reactions. These include cracking and deoxygenation. 2. 2. Intermediate or secondary reactions. These include secondary cracking, oligomerization, olefin formation and cyclization. 3. 3. Terminal or terminating reactions. These include alkylation, isomerization, disproportionation, polymerization and condensation reactions.
243 citations
TL;DR: Key studies defining the DNA alkylation properties and selectivity of a new class of exceptionally potent, naturally occurring antitumor antibiotics including CC-1065, duoc Carmycin A, and duocarmycin SA are reviewed.
Abstract: Key studies defining the DNA alkylation properties and selectivity of a new class of exceptionally potent, naturally occurring antitumor antibiotics including CC-1065, duocarmycin A, and duocarmycin SA are reviewed. Recent studies conducted with synthetic agents containing deep-seated structural changes and the unnatural enantiomers of the natural products and related analogs have defined the structural basis for the sequence-selective alkylation of duplex DNA and fundamental relationships between chemical structure, functional reactivity, and biological properties. The agents undergo a reversible, stereoelectronically controlled adenine-N3 addition to the least substituted carbon of the activated cyclopropane within selected AT-rich sites. The preferential AT-rich non-covalent binding selectivity of the agents within the narrower, deeper AT-rich minor groove and the steric accessibility to the alkylation site that accompanies deep AT-rich minor groove penetration control the sequence-selective DNA alkylation reaction and stabilize the resulting adduct. For the agents that possess sufficient reactivity to alkylate DNA, a direct relationship between chemical or functional stability and biological potency has been defined.
216 citations
TL;DR: In this article, the pyrolysis of surface-immobilized β-alkyl aryl ethers, m ≈ PhOCH 2 CH 2 Ph, m = PhCH 2CH 2 OPh, and m = ε 2.5 µm SiO 2 -1% Al 2 O 3 at 300 °C, where free-radical reactions are suppressed, produces an acceleration in the rate of decomposition and a substantial alteration in the product distribution as a consequence of the solid-solid interactions between the catalyst and substrate.
148 citations
TL;DR: The availability of methyl tert- tert-butyl ether and tert-amyl methyl ether allows tert -butyl and tert -amyl derivatives of phenolic substances to be produced with the attendant advantages as discussed by the authors.
Abstract: Cationic ion-exchange resins, particularly the macroporous variety, are versatile catalysts which offer several advantages over the homogeneous acid catalysts with respect to corrosion, product recovery, selectivity, etc. In some cases, such as etherification of phenols/naphthols with isobutylene/isoamylene, resin catalysts allow the reaction to occur, but the homogeneous catalysts fail. A noteworthy development has been the use of distillation column reactors (DCR) where the exothermicity of the reaction is usefully employed and the resin inventory, for a specified level of conversion and productivity, can be significantly reduced. The availability of methyl- tert -butyl ether and tert -amyl methyl ether allows tert -butyl and tert -amyl derivatives of phenolic substances to be produced with the attendant advantages. The removal of low concentrations of substances like formaldehyde in aqueous medium offers new opportunities for resin catalysts and methylal formation with methanol in DCR has been realized in bringing down formaldehyde concentration from 1 to 2% (wt) to as low as 0.02%. Resin catalysts are useful for oligomerization of olefins like isobutylene, isoamylene, α-methyl styrene, etc.; cross-dimerization of olefins for making precursors for synthetic musks, can also be advantageously carried out. The alkylation of dissolved polyvinyl phenol with isobutylene, with resin catalysts is interesting in several ways. Many close-boiling substances, such as isomeric and non-isomeric phenolic substances, can be separated through selective reactions based on resin catalysts.
139 citations
TL;DR: In this paper, a mesoporous aluminosilicate MCM-41 catalyst was used to accelerate the alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol.
Abstract: Owing to its large molecular size, alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol does not take plAcc using HY zeolite (pore opening 7.4 A) as catalyst even after controlled steaming treatment to increase its mesoporosity; by contrast, novel mesoporous aluminosilicate MCM-41 catalyses this reaction giving rise to 6,8-di-tert-butyl-2-phenyl-2,3-dihydro[4H]benzopyran (arising from intramolecular cyclization of the primary cinnamylphenol) together with 4-tert-butylphenol and small amounts of 6-tert-butyl-2-phenyl-2,3-dihydro[4H]benzopyran.
119 citations
TL;DR: The results show that His is the base catalyst for the dealkylation of the covalent intermediate, but that it is not essential for the initial nucleophilic attack of Asp on the C-1 atom of the haloalkane.
113 citations
111 citations
99 citations
TL;DR: Toluene was alkylated with benzyl chloride and benzyl alcohol using a series of clays (KSF, KSF/0, K0, KP10, K10, KS from Sud Chemie) obtained by treating a bavarian bentonite by different acids and a Hungarian bentonite (Mad) as catalysts in a batch reactor.
Abstract: Toluene was alkylated with benzyl chloride and benzyl alcohol using a series of clays (KSF, KSF/0, K0, KP10, K10, KS from Sud Chemie) obtained by treating a bavarian bentonite by different acids and a Hungarian bentonite (Mad) as catalysts in a batch reactor. The catalysts were characterized by chemical analysis, thermal analysis, nitrogen adsorption, solid state nuclear magnetic resonance, X-ray diffraction. The acidity of these solids was determined by infrared spectroscopy using pyridine as molecular probe. The structure, specific surface area, and distribution of Lewis/Bronsted acidity of these clays can be changed to a great extent by acidic or thermal treatment. The rate of alkylation is related to Bronsted acidity when the substrate is benzy alcohol. When benzyl chloride is used as alkylating agent, the Fe3+ content of the clay controls the activity, and iron containing clays show high activities in spite of their low Lewis acidities.
TL;DR: In this paper, chiral diselenides were synthesized from readily available chiral amines for catalytic addition of diethylzinc to aldehydes provided the secondary alcohols in up to 98 % ee.
TL;DR: Four principal products ofkylation of DNA by the nitrogen mustard bis(2-chloroethyl)methylamine (mechlorethamine; HN2) gave four principal products, derived by mono-alkylation of guanine at N-7 and adenine atN-3 and by cross-linking of Guanine to guaninea or guanines to adenines at these positions.
Abstract: Alkylation of DNA by the nitrogen mustard bis(2-chloroethyl)methylamine (mechlorethamine; HN2) gave four principal products, derived by mono-alkylation of guanine at N-7 and adenine at N-3 and by cross-linking of guanine to guanine or guanine to adenine at these positions. These products were isolated by hydrolysis from DNA at neutral pH, followed by ion-exchange chromatography on SP-Sephadex and reversed phase chromatography on ODS. They were characterized by identification with products from the reaction of nitrogen mustard with adenine or deoxyguanylic acid, and by their UV, mass, and proton magnetic resonance spectra.
TL;DR: In this paper, a detailed investigation of the H/D exchange reaction of benzene was carried out, which is the most simple example of the class of aromatic substitution reactions that includes important processes such as toluene alkylation.
Abstract: Nuclear magnetic resonance (NMR) studies of reactions on solid acids and bases, including zeolites, metal oxides, and metal halides, have characterized persistent intermediates, and the range of these investigations has been extended by monitoring label scrambling. However, there have been no detailed in situ NMR kinetic measurements. We have carried out the first such study, a detailed investigation of the H/D exchange reaction of benzene, which is the most simple example of the class of aromatic substitution reactions that includes important processes such as toluene alkylation. The avoidance of a free cation even for the energetically less demanding reaction studied here suggests that free cations in acid catalysis by zeolites at low temperature may be the exception rather than the rule; indeed, the only such species observed spectroscopically have been exceptionally stable cations. 27 refs., 3 figs.
TL;DR: The sequence specificity of alkylation by FCE 24517 is therefore the most striking yet observed for an alkylating agent of small molecular weight.
Abstract: FCE 24517, a novel distamycin derivative possessing potent antitumor activity, is under initial clinical investigation in Europe. In spite of the presence of a benzoyl nitrogen mustard group this compound fails to alkylate the N7 position of guanine, the major site of alkylation by conventional nitrogen mustards. Characterisation of DNA-drug adducts revealed only a very low level of adenine adduct formation. Using a modified Maxam-Gilbert sequencing method the consensus sequence for FCE 24517-adenine adduct formation was found to be 5'-TTTTGA-3'. A single base modification in the hexamer completely abolishes the alkylation of adenine. Using a Taq polymerase stop assay alkylations were confirmed at the A present in the hexamer TTTTGA and, in addition, in one out of three TTTTAA sequences present in the plasmid utilized. The sequence specificity of alkylation by FCE 24517 is therefore the most striking yet observed for an alkylating agent of small molecular weight.
TL;DR: In this paper, a comparative study of the alkylation of benzene or toluene with MeOH or C{sub 2}H{sub 4} over a medium (ZSM-5) and a large pore ({beta}) zeolite of comparable acidities was carried out.
Abstract: A comparative study of the alkylation of benzene or toluene with MeOH or C{sub 2}H{sub 4} over a medium (ZSM-5) and a large pore ({beta}) zeolite of comparable acidities was carried out. It was observed that the reaction temperature in combination with the structure of the zeolite plays an important role in the reactions that take place. The maximum yield of either the primary or secondary alkylation products may occur at an intermediate temperature, which is lower over {beta} zeolite. Due to its pore structure, {beta} zeolite favors secondary alkylation reactions and also disproportionation reactions of the generated alkylaromatics to a higher extent than ZSM-5 does. MeOH generates both primary and secondary alkylation products, while C{sub 2}H{sub 4} favors oligomerization reactions, primary alkylation reactions, and particularly, disproportionation reactions. Toluene is more reactive than benzene. The aromatic/alkylating agent molar ratio plays an important role in the relative importance of the reactions that take place. The size of the pores of the zeolite in combination with the sizes of the aromatic hydrocarbons and the alkylating agents employed determines whether the alkylation occurs via a Langmuir-Henshelwood (LH) or Rideal-Eley (RE) mechanism. When a LH mechanism occurs, the alkylation rate passes through a maximummore » with respect to the concentration of the aromatic hydrocarbon employed; no such maximum occurs for the RE mechanism.« less
TL;DR: A selective alkylating protocol for phosphorothioate oligonucleotides is developed which is a facile way of generating non-ionic nucleic acids and the problems of gas phase ion generation by matrix assisted laser desorption ionization can be controlled.
Abstract: A method which improves the detectability of DNA by mass spectrometry is presented. By quantitatively alkylating the backbone of phosphorothioate oligonucleotides the problems of gas phase ion generation by matrix assisted laser desorption ionization can be controlled. We have developed a selective alkylating protocol for phosphorothioate oligonucleotides which is a facile way of generating non-ionic nucleic acids. A variety of alkylating agents was studied and their kinetics were monitored in a gel electrophoretic assay and by mass spectrometry.
TL;DR: Aldehyde tosylhydrazones having an adjacent O-isopropylidene group undergo a condensation-fragmentation process in the presence of alkyl magnesium and alkyllithium reagents to yield chiral allyl alcohols as discussed by the authors.
TL;DR: The direct synthesis of coumarin derivatives from m-substituted phenols and α,β-unsaturated carboxylic acids catalysed by solid acid catalysts, such as zeolite H-Beta or Amberlyst-15, in toluene as solvent was studied in this paper.
Abstract: The direct synthesis of coumarin derivatives from m-substituted phenols and α,β-unsaturated carboxylic acids catalysed by solid-acid catalysts, such as zeolite H-Beta or Amberlyst-15, in toluene as solvent was studied. The conversion involves esterification followed by alkylation (ring closure). Ring closure of the ester is promoted both by an appropriate substituent on the aromatic ring and by Michael activation of the β-carbon of the ester. These influences were studied by variation of the reactants. 7-Hydroxy-3,4-dihydrocoumarin is formed in high yield when resorcinol and propenoic acid are used as reactants.
TL;DR: In this article, the authors highlight the advantages of using methyl formate which offers an alternative strategy for the production of basic chemicals via homogeneously catalyzed reactions (hydrogenation, carbonylation, homologation, decarbonylation and alkylation).
Abstract: The present review highlights the advantages of using methyl formate which offers an alternative strategy for the production of basic chemicals via homogeneously catalyzed reactions (hydrogenation, carbonylation, homologation, decarbonylation, alkylation).
TL;DR: Pd(0) catalysed bis- and tris-cyclisation reactions involving aryl-or vinyl-iodides and terminating in Tonnai Friedel-Crafts alkylation of aryal and heteroaryl rings occur regio- and stereo-specifically in good yield.
Patent•
24 Oct 1995TL;DR: In this article, a catalytic composition resulting from mixing at least one aluminum halide, at least quaternary ammonium halide and/or at least amine halohydrate and at least cuprous compound, preferable a halide was proposed.
Abstract: The invention concerns a catalytic composition resulting from mixing at least one aluminum halide, at least one quaternary ammonium halide and/or at least one amine halohydrate and at least one cuprous compound, preferable a halide. The invention also concerns a process for the alkylation of isoparaffins by olefins with that composition.
TL;DR: The alkylation of aniline with methanol was carried out at 673 K on X and Y zeolites exchanged with Li, Na, K, Rb and Cs cations as mentioned in this paper.
Abstract: The alkylation of aniline with methanol was carried out at 673 K on X and Y zeolites exchanged with Li, Na, K, Rb and Cs cations. At low time-on-stream the X catalysts are more active than the Y ones but they deactivate more rapidly. The activity and selectivity were shown to be strongly dependent on the acido-basicity. The selectivity may be oriented towards alkylation on the nitrogen or on the aromatic ring. The study made at equal conversion shows that the selectivity is governed by the balance between the basicity of the oxygen atoms of the framework and the Lewis acidity of the cations in the cages. Generally, the more basic zeolites (X and Y exchanged with K, Rb or Cs) favour the production of N-alkylates, mainly N-methylaniline. The zeolites with the more acidic cations, Li and Na, give rise to C-alkylation (para- or ortho-toluidine and small amounts of 2,4 or 2,6 dimethylaniline and N,N-dimethylparatoluidine). The more basic zeolites display a considerable aging.
TL;DR: In this paper, the carbonaceous deposits formed on LaHY-FAU used in a semi-batch reactor at 353 K to alkylate isobutane with 1-butene have been examined by in situ UV-VIS, FT-IR, and 13C CP/MAS NMR spectroscopies.
Abstract: The carbonaceous deposits formed on LaHY-FAU used in a semi-batch reactor at 353 K to alkylate isobutane with 1-butene have been examined by in situ UV-VIS, FT-IR, and 13C CP/MAS NMR spectroscopies. Only UV-VIS studies evidence unsaturated carbenium ions immediately on adsorption of 1-butene and or 1-butene/isobutane mixture. These ions are part of high molecular weight oligomers (low-temperature carbonaceous deposits) which remain attached to the active site, effecting catalyst deactivation by poisoning. Unsaturated carbenium ion formation is favored by higher reaction temperature (up to 523 K), longer contact times (lower LSHV) and increased Lewis acidity. The presence of isobutane greatly reduces oligomer formation. Thermal treatment of the used catalyst under vacuum causes the low-temperature deposits to desorb from the active site and conversion to aromatics (which remain up to 823 K). The acidic OH groups of the active sites are to a large part regenerated by this treatment yet the initial catalytic activity cannot be fully restored.
Patent•
05 Jun 1995TL;DR: In this article, a method for removing bile salts from a patient that includes administering to the patient a therapeutically effective amount of product produced by a process comprising alkylating one or more crosslinked amine polymers, salts or copolymers thereof with at least one alkylanating agent is described.
Abstract: The invention relates to alkylated amine polymers and a method for removing bile salts from a patient that includes administering to the patient a therapeutically effective amount of product produced by a process comprising alkylating one or more crosslinked amine polymers, salts or copolymers thereof with at least one alkylating agent. The reaction product is characterized in that: (i) at least some of the nitrogen atoms are unreacted with alkylating agent; and (ii) less than 10 mol % of the nitrogen atoms in the polymer react with the alkylating agent to form quaternary ammonium units.
Patent•
15 Jun 1995
TL;DR: In this article, a catalytic composition for the alkylation or transalkylation of aromatic compounds consisting of zeolite Beta, as such or modified by the isomorphic substitution of aluminium with boron, iron or gallium or by the introduction of alkaline/earth-alkaline metals following ion exchange processes, is described.
Abstract: A catalytic composition is described for the alkylation or transalkylation of aromatic compounds consisting of zeolite Beta, as such or modified by the isomorphic substitution of aluminium with boron, iron or gallium or by the introduction of alkaline/earth-alkaline metals following ion exchange processes, and of an inorganic ligand, wherein the extrazeolite porosity, i.e. the porosity obtained by adding the mesoporosity and macroporosity fractions present in the catalytic composition itself, is such as to be composed for a fraction of at least 25% of pores with a radius higher than 100 .ANG..
TL;DR: In this article, the transformation of an isobutane-2-butene mixture with a 41 molar ratio was carried out in liquid phase at 323 K on a USHY zeolite with a framework Si/Al ratio of 4.5.
Abstract: The transformation of an isobutane-2-butene mixture with a 41 molar ratio was carried out in liquid phase at 323 K on a USHY zeolite with a framework Si/Al ratio of 4.5. C5–C14 isoalkanes with about 70 wt.-% of C8 and a small amount of C8 alkenes were obtained. Moreover, about 7% of butene was transformed into undesorbed C10–C30 products containing three unsaturations or cycles. The C5–C14 products resulted from the following reactions: alkylation of isobutane with 2-butene, dimerization of butene, oligomerization-cracking and self-alkylation of isobutane. In order to determine the significance of this latter reaction, the transformation of an isobutane-propene mixture was investigated under similar operating conditions. Trimethylpentanes, and particularly the 2,2,4 isomer, were formed, which confirmed that isobutane self-alkylation was taking place. This reaction was about twice slower than the alkylation of isobutane with propene and twice faster than the dimerization of propene. From the hydrogen balance it was concluded that self-alkylation of isobutane supplied the main part of the hydrogen necessary for the saturation of the products of alkene dimerization and oligomerization-cracking. Hydride transfer would be the limiting step of the formation of isoalkanes. However, isomerization through hydride and methyl shifts of carbenium ion intermediates played also a significant role in the product distribution. This reaction occurred at a rate similar to that of hydride transfer to tertiary carbenium ions but much faster than hydride transfer to secondary carbenium ions.
TL;DR: In this paper, a supported Lewis acid catalyst system for catalyzing hydrocarbon conversion reactions including cationic polymerization, alkylation, isomerization and cracking reactions is disclosed, wherein the catalyst system comprises an inorganic oxide support having immobilized thereon a least one strong Lewis acid comprising at least one metal salt of a strong Bronsted acid.
Abstract: A supported Lewis acid catalyst system for catalyzing hydrocarbon conversion reactions including cationic polymerization, alkylation, isomerization and cracking reactions is disclosed, wherein the catalyst system comprises an inorganic oxide support having immobilized thereon a least one strong Lewis acid comprising at least one metal salt of a strong Bronsted acid wherein the metal is selected from the group consisting of aluminum, boron gallium, antimony, tantalum, niobium, yttrium, cobalt, nickel, iron, tin, zinc, magnesium barium strontium, calcium, tungsten, molybdenum and the metals of the lanthanide series and wherein the strong Bronsted acid is selected from the group consisting of mineral and organic acids stronger than 100% sulfuric acid.