5980-96-1Relevant academic research and scientific papers
Preparation of the novel mesoporous solid acid catalyst UDCaT-4 via synergism of persulfated alumina and zirconia into hexagonal mesoporous silica for alkylation reactions
Yadav, Ganapati D.,Murkute, Ambareesh D.
, p. 389 - 394 (2004)
A novel mesoporous solid acid catalyst named UDCaT-4 was designed by loading persulfated alumina and zirconia (PAZ) into highly oredered, hexagonal mesoporous silica (HMS). UDCaT-4 was characterized by XRD, BET surface area and pore size analysis which revealed that neither pore blocking nor structure collapse of HMS had occurred. NH3-TPD and FTIR were used to determine the acid strength and nature of the sulfate ion retained on the surface of UDCaT-4. It is known that HCl and water have detrimental effects on the activity of the zirconia-based catalyst. Hence, the activity of UDCaT-4 was evaluated in comparsion with that of bulk PAZ in the liquid-phase alkylation of toluene with benzyl chloride and also in the vapour-phase alkylation of mesitylene with isopropanol, where acid and water are generated in-situ, respectively, as co-products. The superior catalytic acivity of UDCaT-4 is atributed to the uniform dispersion of the superacidic centers of PAZ into HMS vis-a-vis bulk PAZ. Reusability and time on-stream studies reveal that UDCaT-4 is a robust and reusable catalyst even in the presence of HCl and H2O.
Cobalt-Catalyzed Kumada Coupling Forming Sterically Encumbered C-C Bonds
Brennan, Marshall R.,Darrow, William T.,Fout, Alison R.,Killion, Jack A.,Leahy, Clare A.
, (2021/12/02)
A Co(acac)3/PN precatalyst was developed and optimized for catalytic Kumada coupling of aryl Grignard reagents to sterically encumbered alkyl halides. The substrate scope demonstrates excellent yields for primary alkyl chlorides and bromides, including good performance using neopentyl chloride and neophyl chloride. Secondary alkyl halides were also successfully arylated in good yields, and the presence of β-hydrogen atoms in a substrate did not inhibit product formation. An intermolecular functional group tolerance screen was conducted which indicates that ester and amide functionality are well tolerated by the reaction conditions. Electrophiles containing ester, pyridine, and nitrile functionality were all coupled with 2-mesitylmagnesium bromide in good yields, supporting tolerance screen results. The intermolecular screen also showed that functional groups which are typically reactive with Grignard reagents such as alcohols and terminal alkynes were not well-tolerated by the reaction.
Efficient cross-coupling of aryl/alkenyl triflates with acyclic secondary alkylboronic acids
Si, Tengda,Li, Bowen,Xiong, Wenrui,Xu, Bin,Tang, Wenjun
supporting information, p. 9903 - 9909 (2017/12/12)
Aryl-secondary alkyl cross-coupling with aryl sulfonate esters as coupling partners remains a significant challenge. Efficient cross-coupling between aryl/alkenyl triflates and acyclic secondary alkylboronic acids is realized for the first time to provide a series of sterically congested acyclic secondary alkyl arenes/olefins in good to excellent yields. The employment of sterically bulky P,PO ligand L1/L2 is crucial for the high yields and selectivities. The method has enabled a concise and 4-step synthesis of a key intermediate of male contraceptive agent and PAF antagonist gossypol.
Efficient synthesis of sterically hindered arenes bearing acyclic secondary alkyl groups by suzuki-miyaura cross-couplings
Li, Chengxi,Chen, Tianyu,Li, Bowen,Xiao, Guolan,Tang, Wenjun
supporting information, p. 3792 - 3796 (2015/03/18)
Bulky P,P-O ligands were designed to inhibit isomerization and reduction side reactions during the cross coupling between sterically hindered aryl halides and alkylboronic acids. Suzuki-Miyaura cross-couplings between di-ortho-substituted aryl bromides and acyclic secondary alkylboronic acids have been achieved with high yields. The method has also enabled the preparation of ortho-alkoxy di-ortho-substituted arenes bearing isopropyl groups in excellent yields. The utility of the synthetic method has been demonstrated in a late-stage modification of estrone and in the application to a new synthetic route toward gossypol. No side reaction: The shown bulky P,P-O ligands (right) successfully inhibit isomerization and reduction side reactions of the cross-coupling of sterically hindered substrates such as di-ortho-substituted aryl bromides with acyclic secondary alkylboronic acids. The method also allows the preparation of ortho-alkoxy di-ortho-substituted isopropyl arenes in excellent yields.
Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents
Vila, Carlos,Giannerini, Massimo,Hornillos, Valentin,Fananas-Mastral, Martin,Feringa, Ben L.
, p. 1361 - 1367 (2014/03/21)
Palladium-catalysed cross-coupling of secondary C(sp3) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation with organolithium reagents, herein we present a Pd-catalysed cross-coupling of secondary alkyllithium reagents with aryl and alkenyl bromides. The reaction proceeds at room temperature and on short timescales with high selectivity and yields. This methodology is also applicable to hindered aryl bromides, which are a major challenge in the field of metal catalysed cross-coupling reactions.
Identification of alkylarene chloromethylation products using gas-chromatographic retention indices
Zenkevich,Makarov
, p. 611 - 619 (2008/03/18)
Gas-chromatographic retention indices on standard nonpolar polydimethylsiloxane stationary phases allow identification of products formed by known organic reactions even without using mass-spectrometric data. The efficiency of this approach was demonstrated by the example of identification of previously uncharacterized chloromethyl derivatives of alkylarenes, including structural isomers of compounds containing several chloromethyl groups, directly in reaction mixtures. Chromatographic analysis of such reaction mixtures allows identification of positional isomers of the starting alkylarenes even when they are present simultaneously. The retention indices were determined for the first time for more than 50 alkyl-(chloromethyl)arenes, by-products of chloromethylation, and chloromethyl derivatives of the simplest alkyl phenyl ketones. Nauka/Interperiodica 2007.
Supercritical hydrogenation and acid-catalysed reactions "without gases"
Hyde, Jason M.,Poliakoff, Martyn
, p. 1482 - 1483 (2007/10/03)
The high temperature catalytic decomposition of HCO2H and HCO2Et are used to generate the high pressure H2 and the supercritical fluids needed for micro-scale hydrogenation of organic compounds; our approach overcomes the problems and limitations of handling high pressure gases on a small-scale and opens the way to the widespread use of continuous supercritical reactions in the laboratory.
Kinetic features of oxidative addition of organic halides to the organonickel σ-complex
Yakhvarov,Budnikova,Sinyashin
, p. 567 - 569 (2007/10/03)
Electrochemically generated organonickel σ-complexes were used as model compounds to study the kinetics of oxidative addition of ArNi Ibpy to RX, the key stage of cross-coupling of organic halides (RX). The reaction rate constants were calculat
Friedel-Crafts alkylation in supercritical fluids: continuous, selective and clean
Hitzler, Martin G.,Smail, Fiona R.,Ross, Stephen K.,Poliakoff, Martyn
, p. 359 - 360 (2007/10/03)
Continuous Friedel-Crafts alkylation of mesitylene C6H3Me3, and anisole, C6H5OMe, with propene or propan-2-ol has been carried out in supercritical propene or CO2 using a heterogeneous polysiloxane-supported solid acid Deloxan catalyst in a small fixed bed reactor (10 ml volume); 100percent selectivity for mono-alkylated products with 50percent conversion could be obtained by adjusting the reaction parameters, e.g. temperature, pressure, flow rates, etc.
Ortho Methyl Group Effects in Cumyl Systems
Timberlake, Jack W.,Pan, Dawei,Murray, Jane,Jursic, Branko S.,Chen, Tonghua
, p. 5295 - 5298 (2007/10/02)
In an attempt to evaluate the steric effect of ortho methyl groups on the stability of the cumyl radical, 2,2',4,4',6,6'-hexamethylazocumene (6) was synthesized and its rate of decomposition was measured.The fact that 6 decomposes 40 times faster than azocumene is attributed to a ground state steric effect.Calculations on the mesitylcumyl radical 1 and cation 2 show both systems to be substantially nonplanar with dihedral angles of 48 deg and 35 deg, respectively.Calculated charge distributions for cation 2 corroborate previously obtained NMR results which showed substantial loss of charge delocalization.
