- Triggering the approach of an arene or heteroarene towards an aldehyde via Lewis acid-aldehyde communication
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The present work reports a combined experimental/computational study of the Lewis acid promoted hydroxyalkylation reaction involving aldehyde and arene/heteroarene and reveals a mechanism in which the rate determining aldehyde to alcohol formation via a four-member cyclic transition state (TS) involves a transfer of hydrogen from arene/heteroarene C-H to aldehyde oxygen with the breaking of the C-H bond and formation of C-C and O-H bonds. The effect of different Sn(iv) derivatives on the hydroxyalkylation reaction from different in situ NMR and computational studies reveals that although the exergonic formation of the intermediate and its gained electrophilicity at the carbonyl carbon drive the reaction in SnCl4 compared to other Sn(iv) derivatives, the overall reaction is low yielding because of its stable intermediate. With respect to different aldehydes, LA promoted hydroxylation was found to be more feasible for an electron withdrawing aldehyde compared to electron rich aldehyde because of lower stability, enhanced electrophilicity gained at the aldehyde center, and a lower activation barrier between its intermediate and TS in the former as compared to the latter. The relative stability of the LA-aldehyde adduct decreases in the order SnCl4 > AlCl3 > InCl3 > BF3 > ZnCl2 > TiCl4 > SiCl4, while the activation barrier (ΔG#) between intermediate and transition states increases in the order AlCl3 4 3 3 4 2 4. On the other hand, the activation barriers in the case of different arenes/heteroarenes are in the order of indole 3, InCl3 and SnCl4 because they have negative free energy of formation (ΔG) for alcohol to the corresponding diaryl methyl carbocation.
- Pratihar, Sanjay
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Read Online
- Indium implantation onto zeolite by pulse arc plasma process for the development of novel catalysts
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Chemical substances that contain both indium (In) and silicon (Si) in close proximity catalyze certain organic chemical reactions. The implantation of In onto zeolite containing Si atoms was carried out by a pulse arc plasma process for the possible devel
- Yoshimura, Satoru,Nishimoto, Yoshihiro,Kiuchi, Masato,Yasuda, Makoto
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Read Online
- Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki-Miyaura Reactions of Diarylmethyl Esters
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The synthesis of triarylmethanes via Pd-catalyzed Suzuki-Miyaura reactions between diarylmethyl 2,3,4,5,6-pentafluorobenzoates and aryl boronic acids is described. The system operates under mild conditions and has a broad substrate scope, including the coupling of diphenylmethanol derivatives that do not contain extended aromatic substituents. This is significant as these substrates, which result in the types of triarylmethane products that are prevalent in pharmaceuticals, have not previously been compatible with systems for diarylmethyl ester coupling. Furthermore, the reaction can be performed stereospecifically to generate stereoinverted products. On the basis of DFT calculations, it is proposed that the oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrate occurs via an SN2 pathway, which results in the inverted products. Mechanistic studies indicate that oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrates to (IPr)Pd(0) results in the selective cleavage of the O-C(benzyl) bond in part because of a stabilizing η3-interaction between the benzyl ligand and Pd. This is in contrast to previously described Pd-catalyzed Suzuki-Miyaura reactions involving phenyl esters, which involve selective cleavage of the C(acyl)-O bond, because there is no stabilizing η3-interaction. It is anticipated that this fundamental knowledge will aid the development of new catalytic systems, which use esters as electrophiles in cross-coupling reactions.
- Dardir, Amira H.,Casademont-Reig, Irene,Balcells, David,Ellefsen, Jonathan D.,Espinosa, Matthew R.,Hazari, Nilay,Smith, Nicholas E.
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p. 2332 - 2344
(2021/06/28)
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- METHOD FOR PRODUCING ARENE COMPOUNDS AND ARENE COMPOUNDS PRODUCED BY THE SAME
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Provided is a method for producing (alkyl)arene compounds represented by Formulae 3-1, 3-2, and 3-3 by the Friedel-Crafts alkylation reaction of alkyl halide compounds and arene compounds using organic phosphine compounds as a catalyst.
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Paragraph 0080
(2021/06/26)
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- Unmodified Fe3O4 nanostructure promoted with external magnetic field: safe, magnetically recoverable, and efficient nanocatalyst for N- and C-alkylation reactions in green conditions
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Transition metal compounds have emerged as suitable catalysts for organic reactions. Magnetic compounds as soft Lewis acids can be used as catalysts for organic reactions. In this report, the Fe3O4 nanostructures were obtained from Fe2+ and Fe3+-salts, under an external magnetic field (EMF) without any protective agent. The X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy tools were used to characterize these magnetic compounds. The two-dimensional (2-D, it showed nanometric size in the two dimensions, nanorod structure) Fe3O4 compound showed high catalytic activity and stability in N- and C-alkylation reactions. A diverse range of N- and C-alkylation products were obtained in moderate to high yield under green and mild conditions in air. Also the N- and C-alkylation products can be obtained with different selectivity and yield by exposure reactions with EMF. Results of alkylation reactions showed that the presence of Fe(II) and Fe(III) species on the surface of magnetic catalysts (phase structure of magnetic compounds) are essential as very cheap active sites. Also, morphology of magnetic catalysts had influence on their catalytic performances. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The catalyst was reused at least four times without any loss of its high catalytic activity for N- and C-alkylation reactions.
- Rafiee, Ezzat,Joshaghani, Mohammad,Abadi, Parvaneh Ghaderi-Shekhi
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p. 2503 - 2522
(2018/01/04)
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- An Efficient Ga(OTf)3/Isopropanol Catalytic System for Direct Reduction of Benzylic Alcohols
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This study aims to report the first gallium-catalyzed direct reduction of benzylic alcohols using isopropanol as a reductant. The reaction proceeds via gallium catalyst-assisted hydride transfer of the in situ-generated benzylic isopropyl ether. The method generates only water and acetone as byproducts and thus provides an atom-economic and environmentally friendly approach to the synthesis of di- and triarylmethanes, which are important substructures in various bioactive compounds and functional materials. (Figure presented.).
- Sai, Masahiro
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supporting information
p. 4330 - 4335
(2018/10/15)
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- Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki Coupling of Trimethylammonium Salts and Arylboronic Acids
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An efficient palladium-catalyzed Suzuki coupling of 1,1-diarylmethyl-trimethylammonium triflates with arylboronic acids is reported. This reaction offers a novel approach to triarylmethane derivatives in good to excellent yields with the palladium-catalyzed C-N bond cleavage as the key feature. Broad substrate scope regarding both reaction partners are observed. Moreover, reactive functional groups such as vinyl and formyl groups are conserved in this transformation.
- Zhang, Zhenming,Wang, Hui,Qiu, Nianli,Kong, Yujing,Zeng, Wenjuan,Zhang, Yongquan,Zhao, Junfeng
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p. 8710 - 8715
(2018/07/21)
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- Synthesis of Di- and Triarylmethanes through Palladium-Catalyzed Reductive Coupling of N -Tosylhydrazones and Aryl Bromides
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A palladium-catalyzed reductive coupling between N-tosylhydrazones and aryl bromides has been developed. The reaction provides an efficient method for the synthesis of diarylmethanes and triarylmethanes via the formation of C(sp2)-C(sp3) single bonds. This new methodology for the synthesis of diarylmethanes and triarylmethanes is featured by the ready availability of the starting materials, mild reaction conditions, and the tolerance of wide range of functional groups. The reaction follows a pathway including palladium carbene formation, migratory insertion, and reduction of the alkylpalladium(II) intermediate.
- Xia, Yamu,Hu, Fangdong,Xia, Ying,Liu, Zhenxing,Ye, Fei,Zhang, Yan,Wang, Jianbo
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p. 1073 - 1086
(2017/02/24)
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- A Zinc Catalyzed C(sp3)?C(sp2) Suzuki–Miyaura Cross-Coupling Reaction Mediated by Aryl-Zincates
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The Suzuki–Miyaura (SM) reaction is one of the most important methods for C?C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross-coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2, in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity.
- Procter, Richard J.,Dunsford, Jay J.,Rushworth, Philip J.,Hulcoop, David G.,Layfield, Richard A.,Ingleson, Michael J.
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p. 15889 - 15893
(2017/10/24)
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- Method for catalytic preparation of triarylmethane compounds by using [EG]2[ZnCl2]
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The invention relates to a method for catalytic preparation of triarylmethane compounds by using [EG]2[ZnCl2], especially to a method for catalytic preparation of the triarylmethane compounds by using a deep eutectic solvent [EG]2[ZnCl2] through Friedel-C
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Paragraph 0093; 0094; 0095; 0096; 0097
(2016/10/09)
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- Benzylic Phosphates in Friedel-Crafts Reactions with Activated and Unactivated Arenes: Access to Polyarylated Alkanes
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Easily reachable electron-poor/rich primary and secondary benzylic phosphates are suitably used as substrates for Friedel-Crafts benzylation reactions with only 1.2 equiv activated/deactivated arenes (no additional solvent) to access structurally and electronically diverse polyarylated alkanes with excellent yields and selectivities at room temperature. Specifically, diversely substituted di/triarylmethanes are generated within 2-30 min using this approach. A wide number of electron-poor polyarylated alkanes are easily accomplished through this route by just tuning the phosphates.
- Pallikonda, Gangaram,Chakravarty, Manab
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p. 2135 - 2142
(2016/03/15)
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- Cine Substitution with Arylzinc Reagents: Scope and Mechanistic Studies
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The unexpected ability of arylzinc reagents bearing electron-donating substituents to react in a Friedel-Crafts fashion (cine) with electrophiles like perpivaloylated glucoside bromide and benzhydryl bromides in competition with organometallic coupling (ipso) is shown. The stereoelectronic factors required to promote the cine reactivity versus the classical ipso, and the mechanism of this alternative pathway, have been investigated. The Wheland intermediate is deprotonated intramolecularly in a 1,2-shift but also in a longer-range shift, leaving in this case the C-Zn untouched. In the latter case, it is possible to take advantage of this result for further functionalization.
- Barroso, Santiago,Lemaire, Sébastien,Farina, Vittorio,Steib, Andreas K.,Blanc, Romain,Knochel, Paul
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p. 2804 - 2816
(2016/04/26)
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- Copper-mediated arylation with arylboronic acids: Facile and modular synthesis of triarylmethanes
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A facile and modular synthesis of triarylmethanes was achieved in good yield via a two-step sequence in which the final step is the copper(II)-catalyzed arylation of diarylmethanols with arylboronic acids. By using this protocol a variety of symmetrical and unsymmetrical triarylmethanes were synthesized. As an application of the newly developed methodology, we demonstrate a highyielding synthesis of the triarylmethane intermediate towards an anti-breast-cancer drug candidate.
- Rao, H. Surya Prakash,Rao, A. Veera Bhadra
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supporting information
p. 496 - 504
(2016/04/05)
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- Arylative Desulfonation of Diarylmethyl Phenyl Sulfone with Arenes Catalyzed by Scandium Triflate
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A scandium-triflate-catalyzed arylative desulfonation of diarylmethyl phenyl sulfones with arenes and heteroarenes was established. A variety of both sulfone and arene substrates were reacted to afford symmetric and nonsymmetric triarylmethanes in good yields. Further transformations of the resulting triarylmethanes and application to the concise synthesis of a bactericidal agent analogue were also demonstrated.
- Nambo, Masakazu,Ariki, Zachary T.,Canseco-Gonzalez, Daniel,Beattie, D. Dawson,Crudden, Cathleen M.
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p. 2339 - 2342
(2016/06/09)
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- In situ activation of benzyl alcohols with XtalFluor-E: Formation of 1,1-diarylmethanes and 1,1,1-triarylmethanes through Friedel-Crafts benzylation
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The Friedel-Crafts benzylation of arenes using benzyl alcohols activated in situ with XtalFluor-E is described. A wide range of 1,1-diarylmethanes and 1,1,1-triarylmethanes were prepared under experimentally simple and mild conditions, without the need for a transition metal or a strong Lewis acid. Notably, the reactivity observed demonstrates the potential of XtalFluor-E to induce C-OH bond ionization and SN1 reactivity of benzylic alcohols. This journal is
- Desroches, Justine,Champagne, Pier Alexandre,Benhassine, Yasmine,Paquin, Jean-Franois
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supporting information
p. 2243 - 2246
(2015/03/04)
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- Simple Method for sp2-sp3 and sp3-sp3 Carbon-Carbon Bond Activation in 2-Substituted 1,3-Diketones
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Simple and efficient methods were developed for sp2-sp3 and sp3-sp3 C-C bond-activation reactions of 2-substituted 1,3-diketones. 3-Substituted 3-bromopentane-2,4-diones were deacylated in the presence of an aromatic compound and a silica gel supported Bronsted acid containing sulfonic groups. The carbocation formed by cleavage of the sp3-sp3 C-C bond of the dione alkylated the aromatic compound.
- Aoyama, Tadashi,Hayakawa, Mamiko,Kubota, Sho,Ogawa, Sumire,Nakajima, Erika,Mitsuyama, Emi,Iwabuchi, Taku,Kaneko, Haruki,Obara, Rina,Takido, Toshio,Kodomari, Mitsuo,Ouchi, Akihiko
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supporting information
p. 2945 - 2956
(2015/09/28)
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- LDA-Mediated Synthesis of Triarylmethanes by Arylation of Diarylmethanes with Fluoroarenes at Room Temperature
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A practical and convenient approach for the secondary C(sp3)-H arylation of diarylmethanes with various fluoroarenes is described. The reaction proceeds smoothly in the presence of LDA (lithium diisopropylamide) at room temperature and affords triarylmethanes in moderate to high yields.
- Ji, Xinfei,Huang, Tao,Wu, Wei,Liang, Fang,Cao, Song
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supporting information
p. 5096 - 5099
(2015/11/03)
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- An improved method for the synthesis of triarylmethanes using heterogenized 12-tungestocobaltic acid
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Two heterogeneous catalysts based on 12-tungestocobaltic acid, including K5CoW12O40 and H5CoW 12O40 supported on rice husk ash extracted nano silica (CoW/NSiO2), were used in sel
- Rafiee, Ezzat,Jalilian, Fereshteh
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p. 203 - 207
(2014/05/20)
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- Benzylation of arenes with benzyl ethers promoted by the in situ prepared superacid BF3-H2O
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An efficient and environmentally friendly benzylation of arenes with benzyl ethers as benzyl donors using BF3-Et2O to generate in situ the superacid BF3-H2O as an efficient promotor has been described. A wide variety of functional groups have been investigated and found to be compatible to give the desired diarylmethanes in yields of up to 99%. The crucial role of the moisture content in this transformation has been demonstrated by detailed investigations. This journal is the Partner Organisations 2014.
- Li, Yu,Xiong, Yan,Li, Xueming,Ling, Xuege,Huang, Ruofeng,Zhang, Xiaohui,Yang, Jianchun
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p. 2976 - 2981
(2014/06/10)
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- Di- and triarylmethylium ions as probes for the ambident reactivities of carbanions derived from 5-benzylated Meldrum's acid
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The kinetics of the reactions of carbocations with carbanions 1 derived from 5-benzyl-substituted Meldrum's acids 1-H (Meldrum's acid=2,2-dimethyl-1,3- dioxane-4,6-dione) were investigated by UV/Vis spectroscopic methods. Benzhydryl cations Ar2CH+ added exclusively to C-5 of the Meldrum's acid moiety. As the second-order rate constants (kC) of these reactions in DMSO followed the linear free-energy relationship lg k=s N(N+E), the nucleophile-specific reactivity parameters N and s N for the carbanions 1 could be determined. In contrast, trityl cations Ar3C+ reacted differently. While tritylium ions of low electrophilicity (E-2) reacted with 1 through rate-determining β-hydride abstraction, more Lewis acidic tritylium ions initially reacted at the carbonyl oxygen of 1 to form trityl enolates, which subsequently reionized and eventually yielded triarylmethanes and 5-benzylidene Meldrum's acids by hydride transfer.
- Chen, Xi,Tan, Yue,Berionni, Guillaume,Ofial, Armin R.,Mayr, Herbert
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supporting information
p. 11069 - 11077
(2014/10/15)
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- NiXantphos: A deprotonatable ligand for room-temperature palladium-catalyzed cross-couplings of aryl chlorides
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Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd-NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp2)-H arylations. The advantages and importance of the Pd-NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides.
- Zhang, Jiadi,Bellomo, Ana,Trongsiriwat, Nisalak,Jia, Tiezheng,Carroll, Patrick J.,Dreher, Spencer D.,Tudge, Matthew T.,Yin, Haolin,Robinson, Jerome R.,Schelter, Eric J.,Walsh, Patrick J.
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supporting information
p. 6276 - 6287
(2014/05/20)
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- Modular synthesis of triarylmethanes through palladium-catalyzed sequential arylation of methyl phenyl sulfone
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Triarylmethanes, which are valuable structures in materials, sensing and pharmaceuticals, have been synthesized starting from methyl phenyl sulfone as an inexpensive and readily available template. The three aryl groups were installed through two sequential palladium-catalyzed C-H arylation reactions, followed by an arylative desulfonation. This method provides a new synthetic approach to multisubstituted triarylmethanes using readily available haloarenes and aryl boronic acids, and is also valuable for the preparation of unexplored triarylmethane-based materials and pharmaceuticals. Unsymmetric triarylmethanes have been synthesized starting from methyl phenyl sulfone as an inexpensive and readily available template. The three aryl groups were installed through two sequential palladium-catalyzed C-H arylation reactions, followed by an arylative desulfonation. Copyright
- Nambo, Masakazu,Crudden, Cathleen M.
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p. 742 - 746
(2014/01/23)
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- Towards a comprehensive hydride donor ability scale
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Rates of hydride transfer from several hydride donors to benzhydrylium ions have been measured at 20 °C and used for the determination of empirical nucleophilicity parameters N and sN according to the linear free energy relationship log k20 °C=sN(N+E). Comparison of the rate constants of hydride abstraction by tritylium ions with those calculated from the reactivity parameters sN, N, and E showed fair agreement. Therefore, it was possible to convert the large number of literature data on hydride abstraction by tritylium ions into N and sN parameters for the corresponding hydride donors, and construct a reactivity scale for hydride donors covering more than 20 orders of magnitude.
- Horn, Markus,Schappele, Ludwig H.,Lang-Wittkowski, Gabriele,Mayr, Herbert,Ofial, Armin R.
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supporting information
p. 249 - 263
(2013/02/25)
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- Additive effects on palladium-catalyzed deprotonative-cross-coupling processes (DCCP) of sp3 C-H bonds in diarylmethanes
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Palladium-catalyzed cross-coupling reactions have become one of the most useful tools in modern organic chemistry. Current methods to achieve direct functionalization of sp3 C-H bonds of arenes and heteroarenes often employ substrates with appropriately placed directing groups to enable reactivity. Examples of intermolecular arylation methods of weakly acidic sp3 C-H bonds in the absence of directing groups, however, are still limited. We describe herein a study on the use of additives in Pd-catalyzed deprotonative-cross-coupling processes (DCCP) of sp3 C-H bonds of diarylmethanes with aryl bromides at room temperature. These studies resulted in development of four new efficient Pd-catalyzed DCCP using additives that enabled the generation of a range of sterically and electronically diverse aryl- and heteroaryl containing triarylmethanes in good to excellent yields. Additive identification and optimization of all reaction conditions (additive loading, solvent and temperature) were performed using high-throughput experimentation (HTE). The approach outlined herein is expected to be generalizable to other C-H functionalization reactions involving the deprotonation of weakly acidic C-H bonds. The Royal Society of Chemistry 2013.
- Bellomo, Ana,Zhang, Jiadi,Trongsiriwat, Nisalak,Walsh, Patrick J.
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p. 849 - 857
(2013/03/28)
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- Palladium-catalyzed diarylmethyl C(sp3)-C(sp2) bond formation: A new coupling approach toward triarylmethanes
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Palladium-catalyzed reductive coupling reactions between N-tosylhydrazones and aryl halides lead to the formation of C(sp3)-C(sp2) bonds. This approach provides a general route for the synthesis of triarylmethanes.
- Xia, Ying,Hu, Fangdong,Liu, Zhenxing,Qu, Peiyuan,Ge, Rui,Ma, Chen,Zhang, Yan,Wang, Jianbo
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supporting information
p. 1784 - 1787
(2013/06/26)
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- Cationic Iron(III) porphyrin catalyzed dehydrative friedel-crafts reaction of alcohols with arenes
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Alcohols react with arenes in the presence of cationic iron(III) porphyrin catalyst. The reaction involves the formation of the C-C bond via dehydration, which is formal Lewis acid catalyzed Friedel-Crafts reaction. Georg Thieme Verlag Stuttgart, New York.
- Teranishi, Satoru,Kurahashi, Takuya,Matsubara, Seijiro
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supporting information
p. 2148 - 2152
(2013/10/21)
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- Palladium-catalyzed C(sp3)-H arylation of diarylmethanes at room temperature: Synthesis of triarylmethanes via deprotonative-cross-coupling processes
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Although metal-catalyzed direct arylation reactions of non- or weakly acidic C-H bonds have recently received much attention, chemists have relied heavily on substrates with appropriately placed directing groups to steer reactivity. To date, examples of intermolecular arylation of unactivated C(sp3)-H bonds in the absence of a directing group remain scarce. We report herein the first general, high-yielding, and scalable method for palladium-catalyzed C(sp3)-H arylation of simple diarylmethane derivatives with aryl bromides at room temperature. This method facilitates access to a variety of sterically and electronically diverse hetero- and nonheteroaryl-containing triarylmethanes, a class of compounds with various applications and interesting biological activity. Key to the success of this approach is an in situ metalation of the substrate via C-H deprotonation under catalytic cross-coupling conditions, which is referred to as a deprotonative-cross-coupling process (DCCP). Base and catalyst identification were performed by high-throughput experimentation (HTE) and led to a unique base/catalyst combination [KN(SiMe3)2/Pd-NiXantphos] that proved to efficiently promote the room-temperature DCCP of diarylmethanes. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of substrates that are known to undergo O-, N-, enolate-, and C(sp2)-H arylation.
- Zhang, Jiadi,Bellomo, Ana,Creamer, Andrea D.,Dreher, Spencer D.,Walsh, Patrick J.
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supporting information; experimental part
p. 13765 - 13772
(2012/10/08)
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- Direct alkylation of aromatics using alcohols in the presence of NaHSO 4/SiO2
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Simple and efficient procedure for alkylation of aromatics from alcohols in the presence of NaHSO4/SiO2 was developed. Various triaryl methanes were obtained in good yields in short reaction time. For instance the reaction of mesitylene with benzhydrol in the presence of NaHSO4/SiO2 gave the corresponding triaryl methane in a quantitative yield. NaHSO4/SiO2 was regenerated by simple treatment and could be recycled eight times without activity loss.
- Sato, Yuta,Aoyama, Tadashi,Takido, Toshio,Kodomari, Mitsuo
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supporting information; experimental part
p. 7077 - 7081
(2012/08/28)
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- Highly efficient method for solvent-free synthesis of diarylmethane and triarylmethane from benzylic alcohols using P2O5/Al 2O3 or P2O5/SiO2 at room temperature
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A highly efficient procedure for the synthesis of triarylmethane and diarylmethane via benzylation of aromatic hydrocarbons from benzyl alcohols using supported P2O5 on SiO2 and/or Al 2O3 under solvent-free conditions is described. Excellent yields of triarylmethane and diarylmethane were obtained using P 2O5-SiO2 (50%W/W) and/or P2O 5-Al2O3 (50%W/W) at room temperature. The reusability of both supported P2O5 on SiO2 and Al2O3 were examined. Both supported reagents show favorable activities in first and second runs, however, a decline in reactivity was observed in following attempts. The reaction is scalable to > 0.03 mole amounts.
- Khazaei, Ardeshir,Rad, Mohammad Navid Soltani,Borazjani, Maryam Kiani,Moradian, Khadijeh Mansouri,Borazjani, Mohammad Kiani,Zebarjadian, Mohammad Hassan
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experimental part
p. 120 - 126
(2012/06/18)
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- Tin exchanged heteropoly tungstate: An efficient catalyst for benzylation of arenes with benzyl alcohol
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The partial exchange of tin with the protons of 12-tungstophosphoric acid (TPA) results in a highly active heterogeneous catalyst for benzylation of arenes with benzyl alcohol as benzylating agent. The catalysts were characterized by X-ray diffraction, Laser-Raman and FT-IR of pyridine adsorption. The catalytic activity depends significantly on the extent of tin exchanged with the protons of heteropoly tungstate. The characterization results suggest the presence of Lewis acidic sites by the exchange of tin. The catalyst with partial exchange of Sn showed high benzylation activity, which in turn related to variation in acidity of the catalysts. The catalyst is highly active for benzylation reaction irrespective of the nature of substituted arenes and benzyl alcohols. These catalysts are highly active compared to other acid catalysts used for benzylation of different arenes. The catalyst is easy to separate from reaction mixture and exhibit consistent activity upon reuse. The plausible reaction mechanism based on the role of both Lewis and Bronsted acid sites of the catalyst was discussed.
- Ramesh Kumar, Ch.,Rao, K.T. Venkateswara,Sai Prasad,Lingaiah
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experimental part
p. 17 - 24
(2011/04/21)
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- Selective benzylic and allylic alkylation of protic nucleophiles with sulfonamides through double Lewis acid catalyzed cleavage of sp3 carbon-nitrogen bonds
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The acid-catalyzed benzylic and allylic alkylation of protic nucleophiles is fundamentally important for the formation of carbon-carbon and carbon-heteroatom bonds, and it is a formidable challenge for benzylic and allylic amine derivatives to be used as the alkylating agents. Herein we report a highly efficient benzylic and allylic alkylation of protic carbon and sulfur nucleophiles with sulfonamides through double Lewis acid catalyzed cleavage of sp3 carbon-nitrogen bonds at room temperature. In the presence of a catalytic amount of inexpensive ZnCl2-TMSCl (TMSCl: chlorotrimethylsilane), 1,3-diketones, β-keto esters, β-keto amides, malononitrile, aromatic compounds, thiols, and thioacetic acid can couple with a broad range of tosylactivated benzylic and allylic amines to give diversely functionalized products in good to excellent yields and with high regioselectivity. Furthermore, the cross-coupling reaction of 1,3-dicarbonyl compounds with benzylic propargylic amine derivatives has been successfully applied to the one-step synthesis of polysubstituted furans and benzofurans.
- Liu, Cong-Rong,Li, Man-Bo,Yang, Cui-Feng,Tian, Shi-Kai
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experimental part
p. 793 - 797
(2009/09/29)
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- Suzuki-miyaura coupling of diarylmethyl carbonates with arylboronic acids: A new access to triarylmethanes
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Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids proceeded in the presence of [Pd(n3-C3H 5)CI]2-DPPPent (1,5- bis(diphenylphosphino)pentane) catalyst, yielding a variety of triarylmethanes.
- Yu, Jung-Yi,Kuwano, Ryoichi
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supporting information; experimental part
p. 973 - 976
(2009/04/07)
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- Molecular iodine-catalyzed benzylation of arenes with benzyl alcohols
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A novel molecular iodine-catalyzed benzylation of arenes with benzyl alcohols has been developed. The reaction can be carried out under mild conditions to afford a series of diarymethane derivatives in high yields and good regioselectivities.
- Sun, Gaojun,Wang, Zhiyong
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p. 4929 - 4932
(2008/09/21)
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- Br?nsted-acid-catalyzed coupling of electron-rich arenes with substituted allylic and secondary benzylic alcohols
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p-Toluenesulfonic acid and triflic acid catalyze efficiently the coupling of electron-rich arenes with allylic and benzylic alcohols. Reactions are conducted under mild conditions, in air, and in the absence of solvent.
- Le Bras, Jean,Muzart, Jacques
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p. 7942 - 7948
(2008/02/08)
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- Suzuki-miyaura cross-coupling reactions of benzyl halides with potassium aryltrifluoroborates
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(Chemical Equation Presented) The palladium-catalyzed cross-coupling of potassium aryltrifluoroborates with benzylic halides occurs in good yield with high functional group tolerance. The increased stability of potassium aryltrifluoroborates compared to other boron coupling partners makes this an effective route to functionalized methylene-linked biaryl systems.
- Molander, Gary A.,Elia, Maxwell D.
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p. 9198 - 9202
(2007/10/03)
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- METHOD FOR ESTABLISHING CC BONDS BETWEEN ELECTROPHILIC SUBSTRATES AND ? - NUCLEOPHILES IN NEUTRAL TO ALKALINE AQUEOUS OR ALCOHOLIC SOLVENTS WITHOUT USING A LEWIS OR BRONSTED ACID
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The invention relates to a method for establishing carbon-carbon bonds by reacting electropohilic substrates that have a solvolysis rate kEtOH (25°C) > 10-6 s-1 and ? compounds. The method is characterized by generating the intermediary carbocations in neutral to alkaline aqueous or alcoholic solvents or solvent mixtures without using a Lewis or Br?nsted acid.
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Page/Page column 18-19
(2008/06/13)
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- Perfluorosulfonylmethide compounds; use thereof for carbon-carbon bond formation
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Free perfluorosulfonylmethide compounds and metal salts thereof show strong catalytic activity in carbon-carbon bond formation reactions, in amounts as low as 0.1 mole %. Fluorous media may be used, especially biphasic fluorous media enabling ready recycling of the catalyst. The formula thereof is: M[C(SO2R1)3?(m+q)(SO2R2)m(SO2R3)q]xwhere M is H, Sc, Y, La, Ce, Pr, Nd, Sm Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Zr, Hf, Th, Nb, Ta, U, Bi, Al, Ga, In or Tl, x is the common oxidation state of a said metal M, R1, R2and R3are perfluorinated or polyfluoronated hydrocarbon, ether or amine moieties or mixtures thereof and m+q=0, 1, 2 or 3 (m and q being zero or integers).
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Page column 13
(2010/02/06)
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- Mechanism of reduction of trityl halides by lithium dialkylamide bases
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Trityl chloride (TCl) and bromide are reduced by hindered lithium dialkylamide bases in THF to give predominantly triphenylmethane and a small amount of trityl dimer. Rate constants for the reduction of TCl by lithium diisopropylamide and lithium tert-butylethylamide in THF at -78 ?C have been measured; the reactions are first order in monomeric base and in trityl chloride. Inter- and intramolecular kinetic isotope effect studies employing β-deuterium substituted bases and substituent effect studies coupled with other kinetic information were used to formulate a scheme for the reactions. The reactions proceed by a rapid predissociation of the trityl halide to form an ion pair containing the trityl-THF oxonium cation followed by diffusion controlled electron transfer (ET) from the monomeric form of the base to the trityl-THF oxonium ion. The radical pair thus formed reacts by fast, highly regioselective β-hydrogen atom transfer from the aminyl radical to the methine carbon of the trityl radical to give triphenylmethane. Radical escape from the cage is a minor competing process. An outer-sphere ET process is energetically acceptable, but an inner-sphere process appears to be more likely.
- Newcomb, Martin,Varick, Thomas R.,Goh, Swee-Hock
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p. 5186 - 5193
(2007/10/02)
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- Photolysis of Triarylacetonitriles. A Novel Photochemical Generation of Phenyl(cyano)carbene
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Upon UV irradiation in methanol, triarylacetonitrile underwent a novel α,α-elimination of two aryl groups to give biaryl and α-methoxyarylacetonitrile.However, when a methoxy group was introduced into the phenyl group, another photochemical process which gave the corresponding triarylmethane and methoxytriarylmethane as major products took place simultaneously.
- Shi, Min,Okamoto, Yoshiki,Takamuku, Setsuo
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p. 1044 - 1054
(2007/10/02)
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- Reactions of some p-Substituted Triphenylmethyl Chlorides with Alcohols, Alkali-metal Alcoholates, and Tributylamine
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The p-methoxylated triphenylmethyl chlorides (4a-c), when heated with alcohols, give mixtures of the corresponding triarylmethanes (5a-c) (via the hydride transfer to the corresponding triarylmethylium cations) and the alkyl (substituted triphenylmethyl) ethers (7a-c) (via polar susbtitution reactions).Part or all of the ether (7c) may be further converted into the substituted triphenylmethanol (6c).In the reaction of the mono-p-methoxylated halides (4a) and (4c) with methanol, the substitution products (7a) and (7c) are formed as the main products, while the main product of the reaction of the di-p-methoxylated halide (4b) with methanol is the substituted triphenylmethane (5b).When the methanol is replaced by 2H4> methanol, no reduction product is formed from the halide (4c).Reaction of halide (4c) with ethanol furnishes exclusively the substituted triphenylmethane (5c).The p-chlorophenyl(diphenyl)methyl chloride (4d) gives, with methanol, mainly or exclusively the ether (7d), and with ethanol, under mild conditions, gives the ether (9d).However, under vigorous conditions, the substituted triphenylmethane (5d) is formed.The reduction of the p-methoxylated triphenylmethyl chloride (4c) by alcohols as well as its conversion into alkyl (p-methoxylated triphenylmethyl) ethers are accompanied, to a certain degree, by exchange of the p-methoxy group of the substrate and the alkoxy group of the alcohol; no similar exchange of the p-chlorine atom of halide (4d) was observed.Explanations for all obsrved diferences are offered.The reactions of the substituted triphenylmethyl chlorides (4b-d) with alkoxides in the corresponding alcohols give the corresponding alkyl (substituted triphenylmethyl) ethers (7b), (7c), (9c), and (9d), respectively, in excellent yields.The reaction of the triarylmethyl chloride (4d) with potassiumt-butoxide in THF in the presence of acetone led, among other products, to the formation of oligomeric material which indicates the operation of single-electron-transfer induced processes.Reaction of the same chloride (4d) with tributylamine in refluxing cumene or t-butylbenzene led to the exclusive formation of a series of products all of which may be derived from the intermediacy of the substituted triphenylmethyl radical (18); the latter, in turn, is thought to arise as a result of dissociative electron transfer from tributylamine to chloride (4d).
- Izso, Gyoengyi,Huszthy, Peter,Lempert, Karoly,Fetter, Jozsef,Simig, Gyula,et al.
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p. 769 - 778
(2007/10/02)
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- NADH Model Studies. Part 2. Cationic Hydrogenations using Acridan Derivatives as Hindered NADH Models.
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Various aryl alcohols (5), arylethylenes (6), and trityl ethers (7) are found to undergo smooth reduction in dichloromethane at room temperature when treated with an equimolar amount of the acridans (3) and trifluoroacetic acid.The limiting acidity value (H0) for the medium in which the compounds (3) are completely protonated and hence not suitable as NADH models was also determined spectrophotometrically.Kinetic studies of reduction of (5) with (3) in dilute sulphuric acid, or Hantzsch ester (2) in glacial acetic acid, indicated that during reduction steric hindrance is important in less acidic media whereas the reduction of cations performed with trifluoroacetic acid is not affected by steric factors.
- Singh, Serjinder,Gill, Sarbjeet,Sharma, Vijay K.,Nagrath, Sarita
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p. 1273 - 1276
(2007/10/02)
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- Single-electron-transfer-initiated Thermal Reactions of Arylmethyl Halides. Part 11. The Reaction of Trityl Halides with Sodium Methoxide in 2,2-Dimethoxypropane
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Trityl chloride (1a) and bromide (1b) furnish with sodium methoxide in 2,2-dimethoxypropane, in addition to several minor products, mixtures of the substitution products methyl trityl ether (1c) and p-methoxytriphenylmethane (2a), and of the reduction products triphenylmethane (1f) and p-diphenylmethyltritylbenzene (3a) which are the products of competing SN and single-electron transfer-initiated processes.Compound (1c) is suggested to be formed via two successive SN' processes rather than by either the SN1 or Sn2 mechanisms which are both disfavoured under the experimental conditions applied.
- Huszthy, Peter,Lempert, Karoly,Simig, Gyula
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p. 1323 - 1330
(2007/10/02)
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- Cationic Hydrogenation of Benzyl Alcohols and Arylethylenes using Acridane Derivatives as Hindered NADH Models
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Secondary and tertiary benzyl alcohols and arylethylenes are efficiently reduced by acridane derivatives (1) in the presence of trifluoroacetic acid in dichloromethane.
- Singh, Serjinder,Chhina, Sarbjeet,Sharma, Vijay K.,Sachdev, Satbir S.
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p. 453 - 454
(2007/10/02)
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- Anomalous Acetoxylation of Aromatic Nuclei: Some Structural Requirements in the Substrate
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For certain aromatic nuclei, bromination in acetic acid in the presence of pyridine is accompanied by nuclear acetoxylation.As first observed with galbulin, when two alkoxyl groups, one meta and one para to a benzylic centre of the substrate are present, acetoxylation occurs at the intervening ortho position.Under the given conditions, acetoxylation occurs at position 8 of 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydronaphthalene, and at position 2 of 3,4-dimethoxy diphenyl and triphenyl-methanes.Acetoxylation does not occur in the absence of either of the alkoxy groups or in the absence of pyridine, not does it occur in the pendant ring of 1-(3',4'-dimethoxyphenyl)-1,2,3,4-tetrahydronaphthalene.These results are consistent with the earlier suggestion that the reaction occurs by way of initial oxidative formation of a doubly benzylic cation
- Bandaranayake, Wickramasinghe M.,Riggs, Noel V.
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p. 115 - 129
(2007/10/02)
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- Kinetic Hydrogen Isotope Effects in Intermolecular Hydride Transfer from Arylalkanes to 9-Arylfluoren-9-yl Cations
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Rates of hydride-ion transfer to a series of 9-phenylfluoren-9-yl cations, substituted in the phenyl group, from triphenylmethane and 4,4'-dimethoxydiphenylmethane have been measured at 30 degC in trifluoroacetic acid solution containing 6percent v/v acet
- Bethell, Donald,Hare, Gerard J.,Kearney, Paul A.
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p. 684 - 691
(2007/10/02)
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