Search Results
Abstract
O-Alkylation of phenol compounds was performed in a continuous flow apparatus under biphasic liquid/liquid conditions and promoted by tetrabutylammonium bromide (TBAB) as a phase-transfer catalyst. The segmented flow that is generated within the flow system is able to afford the desired ethers in high yield and in very short times.
Introduction Alkylation of aromatics is an important step in the preparation of various chemicals used in pharmaceuticals, fine chemicals, agrochemicals etc. Commercial alkylation reactions are carried out via electrophilic
Introduction Friedel–Crafts alkylation is an important class of reactions in organic chemistry. The liquid phase benzylation of benzene and other aromatic compounds by benzyl chloride and benzyl alcohol is an important process
treatment agents, and so on [ 1 ]. With the growing repertoire of applications, the development of efficient methods for the synthesis of N -alkyl morpholines continues to be a challenging and active area of research. The alkylation of morpholine with aryl
A novel method for C–H functionalization of heteroaromatic rings by using continuous-flow reactors is reported. Direct alkylation reactions were investigated under heterogeneous catalytic conditions using simple transition metal catalysts at elevated temperature and pressure. As a model reaction, the alkylation of indole was attempted using cheap Raney® Nickel catalyst. Alcohols served both as alkylating agent and as reaction media. The targeted 3-alkyl-indoles were obtained in moderate to good yield with reasonable selectivity. Transient protection on the N-atom increased the selectivity up to 80%. The scope and limitations were also investigated. In summary, direct alkylation with alcohols represents a rapid (residence time of <1 min) and traceless process with high atom economy (88–92%, in those cases where transient protection was not applied).
Abstract
The alkylation of benzyl chloride has been studied in the gas phase using radiolytically formed carbenium ions as the charged reagents. The intramolecular selectivity of the electrophilic attack, deduced from the composition of the neutral products, is characterized by the comparable reactivity of the aromatic ring and of the halogen atom of the substrate toward the gaseous cations. As to ring alkylation, the reactivity of the ortho positions of benzyl chloride is considerably lower than those of chlorobenzene. The results are compared with pertinent mass-spectrometric data, and discussed in connection with existing models of gas phase aromatic substitution by charged electrophiles.
Rapid alkylations of thiols are performed in a packed-bed flow reactor where potassium carbonate acts as a heterogeneous base in anhydrous solvents at ambient temperature. The reaction also has a high efficiency as the removal of the solvent is the only work up required to isolate the product. The products can be used in a subsequent oxidation which was performed sequentially in semibatch mode. The alkylations of phenol and benzyl amine have been demonstrated on an array of bases, but higher temperatures and longer reaction times are required than with thiols.
Abstract
Alkylation of benzene with 1-alkenes (C6–C18) was performed in liquid phase at 160–200 °C over beta zeolites with Si/A molar ratio 12.5–75.0. With increasing alkyl chain length, the conversion of 1-alkene decreased. The alkylation activity decreased with increasing Si/Al ratio of beta-zeolite. The increase of Si/Al molar ratio was connected with the enhancement of the portion of Lewis acid sites in total acidity of beta zeolites, resulting in greater dimerization/oligomerization activity and consequently in more rapid deactivation of beta-zeolites.
Abstract
Selective synthesis of ethylbenzene by vapor phase alkylation of benzene with diethyl carbonate was carried out over MCM-22 modified by MgO. Characterization results show that the number of Brønsted acid sites on MCM-22 decreased significantly after MgO modification, which resulted in a decrease in activity. The selectivity for ethylbenzene was improved greatly over MCM-22 modified by MgO, which can be attributed to the effective suppression of subsequent alkylation of ethylbenzene by the reduction in Brønsted acid sites.
Abstract
In our invention, FCC (fluid catalytic cracking) dry gas could be used to react with benzene without any special purification, and more than 90% ethylene was converted to ethylbenzene. The phenomenon of carbon deposition over catalyst surface was obvious and leads to a deactivation of catalyst, so it is important to study the behavior of carbon deposition of catalyst during alkylation of benzene. The influence of several factors such as temperature, reaction time, reactant concentration of the amount and the kinetics of carbon deposition were investigated, during which carbon depositing rate equations were obtained for different reactant.
