Effect of the nature of solid metal fluorides on the alkylation kinetics of CH-acids in the presence of onium salts

The selective C-alkylation of ethyl 2-methylacetoacetate by prenyl chloride in the presence of solid metal fluorides proceeds at room temperature with yields of from 2.5 to 87.5% depending on the nature of the deprotonating agent. The alkylation rate increases in going from LiF to CsF. A linear correlation was found between the activation free energy for the alkylation reaction and the crystal lattice energy of the solid metal fluorides. Ion exchange was not observed between tetrabutylammonium chloride and solid KF, CsF, and CaF₂ in acetonitrile. The extent of the exchange with KF·2H₂O over 10 h did not exceed 6%. Deprotonation of ethyl 2-methylacetoacetate by the action of the solid metal fluorides was not observed. Loss of the CH-acid is found in the presence of an onium salt, which varies upon, changing the nature of the deprotonating agent: LiF-NaF=KF (30%), RbF (54%), CsF (90%), CaF₂ (35%).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2690–2696, December, 1989.     

Solid–liquid two‐phase alkylation of tetraethyl methylenebisphosphonate under microwave irradiation

Optimum conditions for the solid–liquid phase alkylation of tetraethyl methylenebisphosphonate are dependent on the nature of the alkyl halide. The benzylation with benzyl bromide takes place efficiently in boiling acetonitrile in the presence of potassium carbonate and a phase transfer catalyst. The ethylation with ethyl iodide was best accomplished under solventless microwave conditions in the presence of cesium carbonate and in the absence of an onium salt. The analogous propylation and butylation were complicated by the formation of mixed esters. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:11–, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20648     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VII. Additional details of the mechanism

Mechanism of metals alkylation with an organic halide in the presence of binary systems has been defined in more detail. It has been shown that the passivating film on the surface of zinc and cadmium is partially preserved in the course of the process, and the reaction in diethyl ether is decelerated due to the competitive adsorption of the organyl halide and diethyl ether on the surface of the reacting metal. The ratelimiting stages of the studied alkylation process have been elucidated basing on the experimental data on the effect of the reagents (organyl halide and alkylated metal) nature on the rate of the steady-state reaction and modeling of the suggested catalytic cycle.     

Selective synthesis of acetic acid from hydrogen and carbon monoxide by homogeneous bimetallic catalysts

Alcohols which are the main products of the reaction of hydrogen and carbon monoxide in onium halide promoted ruthenium systems, are changed to acetic acid with the addition of cobalt carbonyl as the second catalyst component. Among Group VIa-VIIIa transition metal complexes, cobalt carbonyl is the only compound which promoted acetic acid formation when combined with ruthenium carbonyl under the conditions studied. The selectivity to acetic acid varied appreciably with the combinations of solvents and promoters, and exceeded 80% with optimal catalyst composition. The effects of solvents and promoters were investigated together with ¹³C tracer experiments from which the roles of halide anions of onium salts were determined.     

Isobutane Alkylation with Butenes and the Oligomerization of C<Subscript>4</Subscript> Olefins in Supercritical Reagents

The competing reactions of isobutane alkylation with butenes and butene oligomerization under supercritical and ordinary gas-liquid conditions are studied over a variety of catalysts: sulfated zirconia, titania-supported heteropolyacids and tungstia, and chlorinated aluminum-platinum catalyst. Both reactions proceed rapidly, showing no substantial decrease in catalytic activity, under supercritical conditions at 140–165° C and 40–45 atm. By contrast, alkylation and oligomerization in the liquid phase and particularly in the gas phase are accompanied by a rapid deactivation of the catalyst. Passing from ordinary gas-liquid conditions to supercritical conditions dramatically accelerates the reaction and the regeneration of the deactivated catalyst. Reaction selectivity depends significantly on the isobutane/olefins (butenes) (I/Ol) ratio in the initial mixture. At I/Ol = 14, isobutane alkylation with butenes is the main reaction pathway, which results in the complete conversion of the butenes to C₈ alkylation products. The yield of saturated isoalkanes is as high as 70%. Reducing the I/Ol ratio to 0.5 results in the domination of butenes over alkylation.     

Reductive Activation of Arenes: XV. Anionic Products of m-Tolynitrile Reduction with Sodium in Liquid Ammonia, and Their Alkylation

From results of oxidation, protonation, and alkylation of the products arising in one- or two- electron reduction of m-tolunitrile with sodium in liquid ammonia followed a conclusion that these products are respectively anion-radical of the compound and 3-methyl-1-cyano-2,5-cyclohexadienyl anion. The reaction of both reduction products with alkyl halides gives rise to compounds of ipso-alkylation with respect to cyano group: the corresponding alkyltoluenes and 1-alkyl-3-methyl-1-cyclohexadienes. The ratio of these products depends on the structure of alkyl halide. The possibility to prepare selectively m-alkyltoluenes by reaction of the product of two-electron reduction of m-tolunitrile with alkyl halides was demonstrated.     

Soluble polymer-supported catalysts containing pendant quaternary onium salts for the addition reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 15a-d ) with carbon dioxide (CO₂) was carried out using 1 mol % of soluble polymer-supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a-d with CO₂ proceeded very smoothly to give the corresponding five-membered cyclic carbonates ( 16a-d ) in high yields at 90-100°C. The catalytic activity of the soluble polymer-supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer-supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.     

Decomposition mechanism of dinitramide onium salts

Thermal decomposition of dinitramide onium salts proceedsvia the dissociative mechanism when pK _a of the base is lower than 5.0 andvia the monomolecular decay of the anion at pK _a>7.0. On going from the melt to the solid state, the reaction mechanism does not change, and the rate decreases by 1–2 orders of magnitude. No anomalous effects inherent in dinitramide metal salts in the solid phase are observed during decomposition of onium salts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1951–1953, November, 1997     

Insoluble polystyrene-bound quaternary onium salt catalysts for the synthesis of cyclic carbonates by the reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 26a—e ) with carbon dioxide (CO₂) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO₂ proceeded smoothly catalyzed by 1–2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates ( 27a—e ) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back-bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer-supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer-supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc.     

Reaction of Amino Acid Salts with 4-Nitrophenyl Acetate under Solid-Liquid Phase Transfer Conditions

The reaction of amino acid salts with 4-nitrophenyl acetate in a system consisting of a solid phase and organic solvent with catalysis by crown ethers and quaternary onium salts may be carried out both on the phase separation surface and in the organic phase depending on the nature of the participants in the phase transfer catalysis reaction.     

Synthesis of perfluoroalkyl-substituted azines via nucleophilic substitution of hydrogen with perfluoroisopropyl carbanions

Perfluoroisopropyl carbanions generated in situ by treatment of perfluoropropene (HFP) with solid KF in the appropriate solvents add to N-alkylpyridinium, quinolinium, and other azinium salts to give reasonably stable N-alkyldihydroazines containing a perfluoroisopropyl group. In most cases, addition proceeds in position 2 of the heterocyclic ring. Stability of these dihydroazines depends on the nature of the N-alkyl group and other substituents present in the azine ring. The least stable of them were converted into their stable C-trifluoroacetyl derivatives in reaction with trifluoroacetic anhydride. Treatment of N-benzyl- or N-p-methoxybenzyl-2-perfluoroisopropyl dihydroazines with oxidizing agents such as DDQ or cerium(IV) ammonium nitrate results in cleavage of the benzylic C-N bond followed by oxidation of the ring, giving pyridines or quinolines with a perfluoroisopropyl group in the aromatic ring. On the basis of these findings, a new protocol for introduction of perfluoroalkyl substituents into azine rings was elaborated via oxidative nucleophilic substitution of hydrogen. It involves three chemical steps: (i) alkylation of azine with p-MeOC6H4CH2Br, (ii) reaction of the resulting salt with fluorinated carbanions generated in situ from HFP and KF, and (iii) N-deprotection and aromatization of the isolated dihydroazine on treatment with CAN. The first two reactions, (i) and (ii), can be performed as a one-pot operation.     

The Wittig rearrangement of fluorenyl ethers in two-phase system

The Wittig rearrangement of fluorenyl ethers by the use of potassium hydroxide as base in solid phase was readily effected by crown ethers and onium salts, while diamines moderately catalyzed the reaction.     

Synthesis of biodiesel over ZnO/Ca(OH)2/KF catalyst prepared by the grinding method

A novel ZnO/Ca(OH)₂/KF solid base catalyst was prepared by the grinding method and applied to biodiesel synthesis by the transesterification of soybean oil. The effect of various parameters such as KF molar amount, calcination temperature, the amount of catalyst, molar ratio of methanol to oil, reaction temperature, and time on the activity of the catalyst were investigated. The catalysts were characterized by several techniques of thermogravimetry/derivative thermogravimetry, X–ray diffraction, Hammett indicator method, and scanning electron microscopy. The analysis results indicated that the KF interacted with Ca(OH)₂ and formed KCaF₃ phase before calcination of the catalyst. The formed KCaF₃ crystal phase was the main catalytic active component for the catalyst activity. In addition, the basicity of ZnO/Ca(OH)₂/KF was greatly influenced by the different calcination temperates, and the catalyst activity was correlated closely with the basicity. A desired biodiesel yield of 97.6 % was obtained at catalyst amount of 3 %, methanol/oil of 12:1, and reaction time of 1.5 h at 65 °C.     

Ionic liquid and solid HF equivalent amine-poly(hydrogen fluoride) complexes effecting efficient environmentally friendly isobutane-isobutylene alkylation

Isoparaffin-olefin alkylation was investigated using liquid as well as solid onium poly(hydrogen fluoride) catalysts. These new immobilized anhydrous HF catalysts contain varied amines and nitrogen-containing polymers as complexing agents. The liquid poly(hydrogen fluoride) complexes of amines are typical ionic liquids, which are convenient media and serve as HF equivalent catalysts with decreased volatility for isoparaffin-olefin alkylation. Polymeric solid amine:poly(hydrogen fluoride) complexes are excellent solid HF equivalents for similar alkylation acid catalysis. Isobutane-isobutylene or 2-butene alkylation gave excellent yields of high octane alkylates (up to RON = 94). Apart from their excellent catalytic performance, the new catalyst systems significantly reduce environmental hazards due to the low volatility of complexed HF. They represent a new, "green" class of catalyst systems for alkylation reactions, maintaining activity of HF while minimizing its environmental hazards.     

Enantioselective alkylation of beta-keto esters by phase-transfer catalysis using chiral quaternary ammonium salts

Catalytic enantioselective alkylation promoted by a quaternary ammonium salt from cinchonine as a phase transfer catalyst is described. Treatment of cyclo beta-keto esters with alkyl halide under mild reaction conditions afforded the corresponding alpha-alkylated beta-keto esters in moderate to excellent yields with high enantiomeric excesses     

Microwave-assisted solid-phase synthesis of pseudopeptides containing reduced amide bond

Procedures were developed for reducing the reaction time and improving the yield of reductive alkylation in solid phase pseudopeptide synthesis by utilizing microwave irradiation. We chose dipeptides containing the reduced amide bond ψ[CH₂NH] as a model system and optimized the microwave assisted reductive alkylation reaction in solid phase pseudopeptide synthesis using Fmoc chemistry. Under the optimized condition, the reductive alkylation reaction used for incorporating the reduced amide bond into the dipeptides was completed in only 8.5 min, whereas the normal reductive alkylation reaction required a total of 300 min. The purity and yield of the various dipeptides containing the reduced amide bond synthesized in this way are better than those achieved using the reductive alkylation method without microwave irradiation. We chose α helical peptides, which are known as a difficult sequence to synthesize, and incorporated the reduced amide bond by the microwave-assisted reductive alkylation reaction. We successfully synthesized pseudopeptides containing the reduced amide bond as a major product by using the novel microwave-assisted method, whereas the same products were obtained as a minor product when using the reductive alkylation method without microwave irradiation.     

Interference-free coulometric titration of water in lithium bis(oxalato)borate using Karl Fischer reagents based on N-methylformamide

A non-alcoholic coulometric reagent based on N-methylformamide (NMF) was shown to eliminate the severe interference effect caused by the alcohol component of the conventional Karl Fischer (KF) reagent on the battery electrolyte lithium bis(oxalato)borate (LiBOB). For sample amounts up to 240 μg of water, the stoichiometry of the KF reaction deviated only slightly from the ideal 1:1 ratio for the best reagent composition. Both solid and dissolved (in acetonitrile, tetrahydrofuran (THF), and ethylene carbonate/ethyl methyl carbonate) LiBOB were titrated successfully using a Metrohm 756 KF Coulometer with a diaphragm cell. The detection limit was estimated to be 0.5-1 μg of water using 100 ml of reagent in this system.     

Mechanism of the solid state reaction NaCl + KF → NaF + KCl

The mechanism of the solid state displacement reaction NaCl + KF → NaF + KCl was investigated, employing diffusion couples (single crystals), in air at 550°C.The product layer obtained was formed with NaF and (Na, K)Cl solid solution.From cation concentration profiles, photometrically determined, for the NaClz.sfnc;KF and NaCl|KCl systems after annealing at 550°C, and from X-ray diffraction analysis on product layer surfaces for the NaCl|KF system, it was possible to state that the overall process is governed by a cation-counterdiffusion mechanism.A comparison between the diffusion coefficient evaluated through the rate constant and that calculated by means of the Boltzmann-Matano analysis for the system NaClKCl, allows one to deduce that the cations Na⁺ and K⁺ are transported in the (Na, K)Cl solid solution.     

Poisoning Effect of Acid Soluble Oil on Triflic Acid-Catalyzed Isobutane Alkylation

The rate of the isobutane alkylation reaction with secondary butenes catalyzed by trifluoromethanesulfonic acid at –20°C is experimentally found to depend on the concentration of acid soluble oil (ASO), which poisons TfOH. With an increase in the ASO molar fraction from 0.13 to 0.16, the reaction rate decreases by a factor of ten. The Hammett acidity function was determined for TfOH solutions at 25°C in the concentration range from 0 to 0.2 ASO molar fractions. The results obtained suggest that the alkylation reaction rate is proportional to the proton activity in the acid phase determined by the Hammett acidity function.     

The mechanism of 2-methylbutene-2 hydrohalogenation in solid phase

Complexes and reactions of 2-methylbutene-2 with hydrohalogen (HCl, HBr) have been studied in solid phase at 80–150 K. It has been found that 2-methylbutene-2 forms with HX complexes of 1:1 and 1:2 composition. Hydrohalogenation proceeds via the rearrangement of complex 2HX·C₅H₁₀ into complex of the addition product with HX. Kinetic equation depends on the reagents ratio. In excess of HX (1< HX:C₅H₁₀< 10) reaction can be described by the first order kinetic equation. If the ratio HX:C₅H₁₀ is more than 10, reaction is described by polychronous kinetic law. The effective activation energy of solid phase hydrohalogenation does not exceed 20 kJ/mole. The molecular mechanism of hydrohalogenation in solid phase has been proposed.