- Iron-Catalyzed Isopropylation of Electron-Deficient Aryl and Heteroaryl Chlorides
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Traditional methods for the preparation of secondary alkyl-substituted aryl and heteroaryl chlorides challenge both selectivity and functional group tolerance. This contribution describes the use of statistical design of experiments to develop an effective procedure for the preparation of isopropyl-substituted (hetero)arenes with minimal isopropyl to n-propyl isomerization. The reaction tolerates electronically diverse aryl chloride coupling partners, with excellent conversion observed for strongly electron-deficient aromatic rings, such as esters and amides. Electron-rich systems, including methyl- and methoxy-substituted aryl chlorides, were found to be less reactive. Furthermore, the reaction was found to be most successful when heteroaryl chlorides were submitted to the cross-coupling protocol. By mapping substituent effects on reaction selectivity, we were able to show that electron-deficient aryl chlorides are essential for efficient coupling, and use electronic structure calculations to predict the likelihood of successful coupling through the estimation of the electron affinity of each aryl chloride. Moderate isolated yields were achieved with selected aryl chlorides, and moderate to good isolated yields were obtained for all the heteroaryl chlorides coupled. Excellent selectivity was observed when a 2,6-dichloroquinoline was used, allowing mono-substitution on a challenging substrate. (Figure presented.).
- Sanderson, James N.,Dominey, Andrew P.,Percy, Jonathan M.
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supporting information
p. 1007 - 1017
(2017/03/27)
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- Liquid-phase oxidation of isopropyl-meta-xylene to tertiary hydroperoxide
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Fundamental aspects and the mechanism of the reaction of liquid-phase oxidation of isopropyl-meta-xylene to a tertiary hydroperoxide by atmospheric oxygen, initiated by isopropylbenzene hydroperoxide or catalyzed by N-hydroxyphthalimide were studied. It was found that using N-hydroxyphthalimide in the course of oxidation of isopropyl-meta-xylene makes it possible to raise, compared with the initiator (isopropylbenzene hydroperoxide), the oxidation rate and the conversion of the hydrocarbon by a factor of 2-2.5 at a 90-95% formation selectivity of a tertiary hydroperoxide of isopropyl-meta-xylene up to a conversion of 20-25%.
- Frolov,Kurganova,Koshel
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p. 895 - 898
(2015/01/08)
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- Nickel-catalyzed Negishi cross-coupling reactions of secondary alkylzinc halides and aryl iodides
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A general Ni-catalyzed process for the cross-coupling of secondary alkylzinc halides and aryl/heteroaryl iodides has been developed. This is the first process to overcome the isomerization and β-hydride elimination problems that are associated with the use of secondary nucleophiles, and that have limited the analogous Pd-catalyzed systems. The impact of salt additives was also investigated. It was found that the presence of LiBF4 dramatically improves both isomeric retention and yield for challenging substrates.(Figure Presented)
- Joshi-Pangu, Amruta,Ganesh, Madhu,Biscoe, Mark R.
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supporting information; experimental part
p. 1218 - 1221
(2011/04/27)
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- PROCESS FOR PRODUCING ALKYLAROMATIC COMPOUND
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A process is provided for producing an alkyl aromatic compound having substituents at the 3- and 5-positions by alkylating an aromatic compound having two substituents in the meta positions with an olefin having 2 to 4 carbon atoms in the presence of a Broensted acid, followed by addition of a Lewis acid and isomerization in the copresence of the Broensted acid and the Lewis acid. According to the present invention, 3,5-dimethylethylbenzene, 3,5-dimethylcumene, etc. may be produced in a stable manner with high yield and high selectivity under mild and simple reaction conditions. The alkyl aromatic compounds having substituents at the 3- and 5-positions are useful as intermediates for functional chemicals for use in pharmaceutical, agricultural and electronic materials. With the method of the present invention, the catalyst used can be recovered and recycled. Thus, desired alkyl aromatic compounds may be obtained economically in an industrially advantageous manner while reducing the load on the environment.
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Page/Page column 6
(2008/06/13)
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- Isopropylation of xylenes catalyzed by ultrastable zeolite Y (USY) and some other solid acid catalysts
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The isopropylation of all three xylene isomers was carried out over ultrastable zeolite Y (USY) catalyst to give corresponding dimethyl (1-methylethyl) benzenes, or in other words dimethyl cumenes (DMCs), using isopropanol as alkylating agent. The effect of reaction temperature, space velocity, substrate-to-alkylating-agent molar ratio, and time-on-stream on conversion of xylene isomers and selectivity to dimethyl cumene was studied. Isopropylation of xylenes over USY gives quite high (80 to 95%) DMC selectivity among the dimethyl cumenes, along with a 70-90% yield of DMCs in total products with respect to limiting reagents, i.e., isopropylating agents at relatively low reaction temperatures (423 ± 10 K) and at quite high xylene conversions (85-97% of theoretical maximum value). The solid acid catalysts zeolites H-Y, H-beta, H-mordenite, as well as silica-alumina and sulfated zirconia, were included for comparative studies in the isopropylation of m-xylene.
- Patra, Chitta Ranjan,Kumar, Rajiv
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p. 216 - 224
(2007/10/03)
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