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Formation of Acyclic cis-Azobenzene without Light
Reduction mixture of bis(4-nitrobenzyl) ether contained a considerable amount of cis-4,4'-dimethylazobenzene.
Tamaoki, Nobuyuki,Yoshimura, Sawako,Yamaoka, Tsuguo
p. 2011 - 2012
(1991)
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Extended scope of in situ iodotrimethylsilane mediated selective reduction of benzylic alcohols
Iodotrimethylsilane, generated in situ from chlorotrimethylsilane and sodium iodide in acetonitrile, selectively reduces moderately electron deficient benzylic alcohols to the analogous toluenes; other reduction sensitive functional groups such as ketone, aldehyde, nitrile, and nitro are unaffected.
Cain,Holler
p. 1168 - 1169
(2001)
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Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
p. 13337 - 13347
(2021/11/20)

Palladium and Nickel Catalyzed Suzuki Cross-Coupling with Alkyl Fluorides
Suzuki cross-coupling of benzylic and unactivated aliphatic fluorides with aryl- and alkenylboronic acids has been achieved via mechanistically distinct Pd and Ni catalyzed pathways that outperform competing protodeboronation, β-hydride elimination, and h
Balaraman, Kaluvu,Wolf, Christian
supporting information
p. 8994 - 8999
(2021/11/20)

Dual copper- and photoredox-catalysed C(sp2)-C(sp3) coupling
The use of copper catalysis with visible light photoredox catalysis in a cooperative fashion has recently emerged as a versatile means of developing new C-C bond forming reactions. In this work, dual copper and photoredox catalysis is exploited to effect C(sp2)-C(sp3) cross-couplings between aryl boronic acids and benzyl bromides.
McLean, Euan B.,Gauchot, Vincent,Brunen, Sebastian,Burns, David J.,Lee, Ai-Lan
supporting information
p. 4238 - 4241
(2019/04/30)

Chlorotrimethylsilane and Sodium Iodide: A Remarkable Metal-Free Association for the Desulfurization of Benzylic Dithioketals under Mild Conditions
A novel metal-free process allowing the reductive desulfurization of various benzylic dithioketals to afford diarylmethane and benzylester derivatives with good to excellent yields is reported. At room temperature, this mild reduction process requires only the use of TMSCl and NaI in CH2Cl2 and tolerates a large variety of functional groups. (Figure presented.).
Zhao, Guangkuan,Yuan, Ling-Zhi,Alami, Mouad,Provot, Olivier
p. 2522 - 2536
(2018/05/14)

Unmodified Fe3O4 nanostructure promoted with external magnetic field: safe, magnetically recoverable, and efficient nanocatalyst for N- and C-alkylation reactions in green conditions
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
p. 2503 - 2522
(2018/01/04)

Decarboxylative Benzylation of Aryl and Alkenyl Boronic Esters
The copper-catalyzed decarboxylative benzylation of aryl and alkenyl boronic esters with electron-deficient aryl acetates is reported. The oxidative coupling proceeds under mild, aerobic conditions and tolerates a host of potentially reactive electrophilic functional groups that would be problematic with traditional benzylation methods (aryl iodides and bromides, protic heteroatoms, aldehydes, Michael acceptors). A reaction pathway in which a benzylic nucleophile is generated by aryl acetate decarboxylation and in turn is intercepted by the catalyst to form diarylmethane products is supported by mechanistic studies.
Moon, Patrick J.,Fahandej-Sadi, Anis,Qian, Wenyu,Lundgren, Rylan J.
supporting information
p. 4612 - 4616
(2018/03/26)

Substrate switchable Suzuki-Miyaura coupling for benzyl ester: Vs. benzyl halide
Two reaction conditions were developed to accomplish the substrate switchable Suzuki-Miyaura coupling of benzyl derivatives and arylboronic acid derivatives. Under conditions for esters, benzyl esters such as carbonates and acetates reacted with arylboronic acids to afford the corresponding diarylmethanes. However, the benzyl halides did not react under the same conditions. On the other hand, benzyl halides such as bromides and chlorides furnished diarylmethanes under conditions for halides, under which benzyl ester substrates did not react, in which water was found to play an important role. This switching system was tested using the intermolecular/intramolecular competitive reactions, during which the desired products could be synthesized by selecting the appropriate reaction conditions.
Ohsumi, Masato,Ito, Akitaka,Nishiwaki, Nagatoshi
p. 35056 - 35061
(2018/10/24)

Synthesis of zwitterionic palladium complexes and their application as catalysts in cross-coupling reactions of aryl, heteroaryl and benzyl bromides with organoboron reagents in neat water
N-(3-Chloro-2-quinoxalinyl)-N′-arylimidazolium salts (aryl = 2,6-diisopropylphenyl [HL1Cl]Cl, aryl = mesityl [HL2Cl]Cl) have been synthesized by treating 2,3-dichloroquinoxaline with the corresponding N′-arylimidazole in neat water. Facile reactions of these imidazolium salts with Pd(PPh3)4 and Pd2(dba)3/PPh3 (dba = dibenzyledene acetone) at 50 °C have afforded zwitterionic palladium(ii) complexes [Pd(HL1)(PPh3)Cl2] (I) and [Pd(HL2)(PPh3)Cl2] (II) in excellent yields. I and II have been tested for their ability to catalyze Suzuki-Miyaura cross coupling (SMC) reactions in neat water/K2CO3 and are found to be highly active for carrying out these reactions between aryl bromides and organoboron reagents. Furthermore, the scope of the catalyst I was also examined by employing (hetero)aryl bromides, hydrophilic aryl bromides, benzyl bromides and various organoboron reagents. More than 80 aryl/benzyl bromide-arylboronic acid combinations were screened in neat water/K2CO3 and it was found that I was a versatile catalyst, which produced biaryls/diarylmethanes in excellent yields. A TON of 82 000 was achieved by using I. Studies on the mechanism have also been carried out to investigate the involvement of carbene complexes in the catalytic path. Poison tests and a two-phase test were also conducted and the results are reported.
Ramakrishna,Dastagiri Reddy
p. 8598 - 8610
(2017/07/12)

Synthesis of Benzyltributylstannanes by the Reaction of N-Tosylhydrazones with Bu3SnH
An efficient stannylation process with N-tosylhydrazones or directly with carbonyl compounds has been developed. A series of functionalized benzyl- and alkyltributylstannanes can be synthesized in moderate to good yields under transition-metal-free conditions. Tandem transformations involving stannylation/Stille cross-coupling reaction have been carried out without purification of the benzyltributylstannane intermediates to afford a series of diarylmethane derivatives.
Qiu, Di,Wang, Shuai,Meng, He,Tang, Shengbo,Zhang, Yan,Wang, Jianbo
p. 624 - 632
(2017/04/26)

Exhibition of the br?nsted acid-base character of a schiff base in palladium(ii) complex formation: Lithium complexation, fluxional properties and catalysis of suzuki reactions in water
The reaction of the dialdehyde N,N-di(α-formylpyrrolyl-α-methyl)-N-methylamine 1 with two equiv. of 2,6-diisopropylaniline yielded two Schiff bases: bis(iminopyrrolylmethyl)amine (H2L) and its hydrolyzed monoimino compound (H2L′) after column separation. The dimeric lithium complex [(HL)Li]2 (2) containing the monoanionic form of H2L was obtained by treating H2L with nBuLi. The presence of both proton donors and acceptors causes the diimino compound H2L to undergo tautomerization to exhibit an amine-azafulvene structure, though the central amine nitrogen competes for a proton. As a result, in the presence of Pd2+ ions, the cationic complex [Pd(Cl)(H2L)][Cl] (3) containing one pendant amine-azafulvene arm and the protonated central amine nitrogen was obtained. Its X-ray structure showed that the bond distances are reversed for the imino-pyrrole moiety relative to those in the structure of H2L. However, the reaction of H2L with [Pd(OAc)2] afforded the neutral complex [PdL] (4) containing the dianionic form of the ligand. The reaction of H2L′ with [PdCl2(PhCN)2] yielded a zwitterionic complex [PdCl2(H2L′)] (5) owing to the presence of the central amine nitrogen. The formation of these palladium complexes with the features mentioned above can be explained by invoking the Br?nsted acid-base character of the Schiff base. Complex 4 is fluxional owing to the up and down movements of the palladium square plane formed by two 5-membered palladacycles, which causes the interconversion of its enantiomers and is studied by the variable temperature 1H NMR method. Furthermore, both complexes 3 and 4 are precatalysts for the Suzuki-Miyaura cross-coupling reaction in water. Sterically encumbered and electronically different substrates including activated aryl chlorides and benzyl halides gave the coupled products in very good yields. The reaction proceeds even at room temperature and in the presence of a large excess amount of mercury. This journal is
Kumar, Rajnish,Mani, Ganesan
p. 6896 - 6908
(2015/04/14)

Diarylmethanes through an Unprecedented Palladium-Catalyzed C-C Cross-Coupling of 1-(Aryl)methoxy-1 H-Benzotriazoles with Arylboronic Acids
1-(Aryl)methoxy-1H-benzotriazoles (ArCH2OBt) are bench-stable reagents that are prepared readily from 1H-benzotriazol-1-yl-4-methylbenzenesulfonate and benzylic alcohols. These compounds, which contain a N-O-C bond, undergo cross-coupling with arylboronic acids by C-O bond scission with catalysts that comprise Pd(OAc)2 and biarylphosphine ligands. Such reactivity of ArCH2OBt derivatives, which lead to diarylmethanes, has not been described previously and constitutes a new activation of benzylic alcohols. With regard to the various ligand-metal complexes that support catalytic activity, it appears that those with smaller "percent buried volumes" (%Vbur) provide better outcomes. This factor has been evaluated in the initial optimization studies and in further reactions with difficult coupling partners. Ligand electronics of the biaryl moiety seem to play a lesser role in this type of reaction. The biscoordinating bis[(2-diphenylphosphino)phenyl] ether appears to be suitable to improve the yields of low-yielding reactions. Phosphine fine: 1-(Aryl)methoxy-1H-benzotriazoles (ArCH2OBt), which contain a N-O-C bond, undergo cross-coupling with arylboronic acids by C-O bond scission with catalysts that comprise Pd(OAc)2 and biarylphosphine ligands. Such reactivity of ArCH2OBt derivatives, which lead to diarylmethanes, has not been described previously and constitutes a new activation of benzylic alcohols.
Singh, Manish K.,Lakshman, Mahesh K.
p. 4156 - 4162
(2016/01/09)

Visible light mediated efficient oxidative benzylic sp3 C-H to ketone derivatives obtained under mild conditions using O2
A photooxygenation of benzylic sp3 C-H reaction has been demonstrated using O2 mediated by visible light. This protocol provides a simple and mild route to obtain ketones from benzylic sp3 C-H bonds. Various benzylic sp3 C-H bonds can be transformed into the desired ketone derivatives in moderate to good yields. The 18O2 labelling experiments demonstrated that the oxygen introduced into ketone originated from dioxygen. A plausible mechanism has been proposed accordingly.
Yi, Hong,Bian, Changliang,Hu, Xia,Niu, Linbin,Lei, Aiwen
supporting information
p. 14046 - 14049
(2015/09/15)

N-heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed Suzuki-Miyaura coupling of benzyl sulfonates with arylboronic acids
The first example of palladium-catalyzed Suzuki-Miyaura coupling between benzyl sulfonates and arylboronic acids was reported in this paper. In the presence of a well-defined, air-stable and easily available NHC-Pd(ii)-Im complex, all reactions worked well to give the desired products in good to almost quantitative yields under the optimal conditions. Electron-rich, -neutral, -poor and sterically-hindered substituents on both substrates are tolerated in such transformation, providing a convenient, efficient and alternative method for the synthesis of diarylmethanes.
Wang, Xiao-Xia,Xu, Bin-Bin,Song, Wen-Ting,Sun, Kai-Xin,Lu, Jian-Mei
p. 4925 - 4930
(2015/05/05)

Direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides
The direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides proceeded in the absence of coordinating ethereal solvents at ambient temperature without the addition of a catalyst. The C(sp2)-C(sp3) cross-coupling showed excellent functional-group tolerance, and products were isolated in high yields, generally without the requirement for purification by chromatography. This process represents an expedient, operationally simple method for the construction of new C(sp2)-C(sp3) bonds. Zinc and you'll miss it. Direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with alkyl halides proceeded rapidly at ambient temperature without a coordinating ethereal solvent or an added catalyst (see scheme). This versatile, operationally simple approach to C(sp2)-C(sp3) bond formation enables the expedient construction of a diverse array of carbon-based structural motifs.
Dunsford, Jay J.,Clark, Ewan R.,Ingleson, Michael J.
supporting information
p. 5688 - 5692
(2015/05/19)

Efficient synthesis of diarylmethane derivatives by PdCl2 catalyzed cross-coupling reactions of benzyl chlorides with aryl boronic acids in aqueous medium
The research provides a simple and efficient method for preparing diarylmethane derivatives using the cross-coupling reaction of benzyl chlorides and aryl boronic acids catalyzed by palladium chloride in DMF aqueous solution without additional ligand.
Zhao, Guangkuan,Zhang, Kena,Wang, Liang,Li, Jingya,Zou, Dapeng,Wu, Yangjie,Wu, Yusheng
supporting information
p. 6700 - 6703
(2016/02/03)

Cucurbit[7]uril promoting PdCl2-catalyzed cross-coupling reaction of benzyl halides and arylboronic acids in aqueous media
The research provides a novel approach for producing diarylmethane derivatives using CB[7]-NaCl-PdCl2catalyzed Suzuki cross-coupling reaction of benzyl chloride derivatives and arylboronic acids in ethanol aqueous solution.
Zhao, Guangkuan,Wang, Zhen,Wang, Ruixin,Li, Jingya,Zou, Dapeng,Wu, Yangjie
supporting information
p. 5319 - 5322
(2015/01/16)

Development of the direct Suzuki-Miyaura cross-coupling of primary B-alkyl MIDA-boronates and aryl bromides
The development of a palladium-catalyzed sp3-sp2 Suzuki-Miyaura cross-coupling of B-alkyl-N-methyliminodiacetyl (B-alkyl MIDA) boronates and (hetero)aryl bromides is reported. This transformation is tolerant of a variety of functional groups (F, NO2, CN, Cl, COCH3, and CHO). B-Alkyl MIDA boronates allow an efficient cross-coupling reaction directed toward the synthesis of unsymmetrical methylene diaryls as well as alkylated arenes in good to excellent yields.
St. Denis, Jeffrey D.,Scully, Conor C. G.,Lee, C. Frank,Yudin, Andrei K.
supporting information
p. 1338 - 1341
(2014/04/03)

Visible light photoredox-catalyzed deoxygenation of alcohols
Carbon-oxygen single bonds are ubiquitous in natural products whereas efficient methods for their reductive defunctionalization are rare. In this work an environmentally benign protocol for the activation of carbon-oxygen single bonds of alcohols towards a reductive bond cleavage under visible light photocatalysis was developed. Alcohols were activated as 3,5-bis(trifluoromethyl)-substituted benzoates and irradiation with blue light in the presence of [Ir(ppy)2( dtb-bpy)](PF6 ) as visible light photocatalyst and Hünig's base as sacrificial electron donor in an acetonitrile/water mixture generally gave good to excellent yields of the desired defunctionalized compounds. Functional group tolerance is high but the protocol developed is limited to benzylic, α-carbonyl, and α-cyanoalcohols; with other alcohols a slow partial C-F bond reduction in the 3,5-bis(trifluoromethyl)benzoate moiety occurs.
Rackl, Daniel,Kais, Viktor,Kreitmeier, Peter,Reiser, Oliver
p. 2157 - 2165
(2015/01/09)

Metal-free carbon-carbon cross-couplings between the ion pairs in sulfonium tetraphenylborates
A series of sulfonium tetraphenylborates can be readily prepared by the metathesis of sulfonium halides with sodium tetraphenylborates. After heating at 120-150 °C, the sulfonium tetraphenylborates can smoothly undergo the cross-couplings between the tetraphenylborate anions and the sulfonium cations in the absence of a metal catalyst. For carbonylmethyl-, benzyl-, and allylsulfoniums, the corresponding carbonylmethyl-phenyl, benzyl-phenyl, and allyl-phenyl cross-coupling products can be obtained in 22-76% yields. An interionic electron-transfer mechanism for this cross-coupling reaction is proposed.
Xu, Mei-Li,Huang, Wenhua
p. 4230 - 4232
(2014/07/22)

A highly efficient catalyst for Suzuki-Miyaura coupling reaction of benzyl chloride under mild conditions
Diarylmethane derivatives, essential building blocks in organic synthesis, are usually synthesized through the traditional electrophilic substitution reaction i.e., Friedel-Crafts reaction, which suffers from the rearrangement and weak reactivity of aromatic compounds with deactivating/electron-withdrawing groups. The Suzuki-Miyaura coupling reaction of low-cost benzyl chloride as an alternative method overcomes these defects. Pd(ii) organometallic catalysts immobilized on the triphenylphosphine-functionalized microporous knitting aryl polymer (KAPs(Ph-PPh3)-Pd) as a novel heterogeneous catalyst was employed in Suzuki-Miyaura coupling reaction of benzyl chloride and exhibited excellent catalytic activity under mild conditions with a turnover frequency (TOF) up to 76 min-1 (4569 h-1). This work reveals that the microporous structure of the catalyst can rapidly adsorb substrates, consequently facilitating their interaction, and eventually promoting the catalytic efficiency. the Partner Organisations 2014.
Guan, Zhenhong,Li, Buyi,Hai, Guoliang,Yang, Xinjia,Li, Tao,Tan, Bien
p. 36437 - 36443
(2014/11/08)

Indium(III) triflate - A catalyst for greener aromatic alkylation reactions
An environmentally friendly method for alkylating aromatic compounds with simple alcohols in the presence of a catalytic amount of indium(III) triflate is reported. Ionic liquids are used as solvents and energy-efficient heating is provided by microwave radiation. Good yields are obtained with benzyl, secondary, and tertiary alcohols. Simple primary alcohols are not effective alkylating agents under these conditions. With tertiary alcohols, activated aromatic compounds such as toluene and anisole must be used to obtain good yields. The catalyst, which is immobilized in a water-insoluble ionic liquid, can be easily recycled without significant loss of activity.
Mack, Ryan,Askins, Grant,Lowry, Jacob,Hurley, Nathan,Reeves, Perry C.
p. 1262 - 1265
(2014/01/06)

Direct electrosynthesis of ketones from benzylic methylenes by electrooxidative C-H activation
Electrify your chemistry! Direct electrosynthesis of ketones from benzylic methylenes in an undivided cell was realized in moderate to good yields (see scheme). In this electrosynthesis, electrons instead of conventional oxidants and catalysts are employed to make the reaction environmentally benign. Moreover, the reaction intermediate radical was detected by ESR spectroscopy and the reaction mechanism was clarified.
Meng, Li,Su, Jihu,Zha, Zhenggen,Zhang, Li,Zhang, Zhenlei,Wang, Zhiyong
supporting information
p. 5542 - 5545
(2013/05/23)

Microwave-promoted palladium catalysed Suzuki cross-coupling reactions of benzyl halides with arylboronic acid
Simple catalytic systems for the coupling of benzyl halides with phenylboronic acid under microwave conditions were tested. Microwave-promoted Suzuki reaction of arylboronic acid with benzyl halides catalysed by PdCl2(PPh3)2 in the mixed solvents DMF/H2O is reported to give diaryl methane derivatives in good to high yield.
Zhang, Yu-Quan
p. 375 - 376
(2013/07/26)

[Pd(PPh3)2 (saccharinate)2]- general catalyst for Suzuki-Miyaura, Negishi cross-coupling and C-H bond functionalization of coumaryl and pyrone substrates
The potential of complex [Pd(PPh3)2(saccharinate) 2] 1 in catalyzing Suzuki-Miyaura cross-coupling of 4-halo and 4-bromomethyl coumaryl and pyrone substrates with different aryl boronic acids has been explored. Excellent yields of the desired products are obtained in competitive reaction time and under relatively mild conditions. Negishi cross-coupling of 4-coumaryl tosylate with aryl and alkylzinc reagents has also been performed with good yields of the cross-coupled products obtained in most cases. Intra-molecular C-H bond functionalization of coumaryl ethers also furnished very high yields of synthetically attractive tetracyclic ring systems exhibiting the potential of 1 as a powerful catalyst in synthetically important reactions.
Shah, Parin,Santana, M. Dolores,García, Joaquín,Serrano, J. Luis,Naik, Minal,Pednekar, Suhas,Kapdi, Anant R.
supporting information
p. 1446 - 1453
(2013/02/25)

Aluminum triflate as a powerful catalyst for direct amination of alcohols, including electron-withdrawing group-substituted benzhydrols
Direct aminations of allylic alcohols, benzylic alcohols, and benzhydrols with electron-withdrawing (F, Br, I, NO2, or CN) substituents were efficiently catalyzed by aluminum triflate [Al(OTf)3] to afford the corresponding biarylamines in high yield, and the dibromo-substituted product was further transformed into letrozole. Copyright
Ohshima, Takashi,Ipposhi, Junji,Nakahara, Yasuhito,Shibuya, Ryozo,Mashima, Kazushi
supporting information
p. 2447 - 2452
(2012/11/07)

Reduction of carbonyl to methylene: Organosilane-Ga(OTf)3 as an efficient reductant system
Direct carbonyl reduction to methylene has been achieved by mild reductant system obtained from the combination of organosilane and gallium (III) trifluoromethanesulfonate {Ga(OTf)3}, a water tolerant, recyclable, catalyst. Among a series of organosilanes studied, dimethylchlorosilane (Me 2SiHCl, DMCS) showed the highest efficiency. Both aromatic and aliphatic ketones were effectively reduced to the corresponding methylene products with high functional groups tolerance, under very mild conditions in a relatively short period of time with good to excellent yields. Graphical Abstract: [Figure not available: see fulltext.]
Surya Prakash,Do, Clement,Mathew, Thomas,Olah, George A.
experimental part
p. 507 - 511
(2012/01/04)

Palladium-catalyzed decarboxylative coupling of potassium nitrophenyl acetates with aryl halides
A palladium-catalyzed decarboxylative cross-coupling of potassium 2- and 4-nitrophenyl acetates with aryl chlorides and bromides has been developed. Because the nitro group can be readily converted to many other functional groups, the new reaction provides a useful method for the preparation of diverse 1,1-diaryl methanes and their derivatives.
Shang, Rui,Huang, Zheng,Chu, Ling,Fu, Yao,Liu, Lei
supporting information; experimental part
p. 4240 - 4243
(2011/10/09)

Deoxygenation of benzylic alcohols using chloroboranes
New boron-based methods for deoxygenating benzylic alcohols via the corresponding alkoxides are reported.
Yao, Min-Liang,Pippin, Adam B.,Kabalka, George W.
scheme or table
p. 853 - 855
(2010/03/24)

Palladium nanoparticle catalyzed hiyama coupling reaction of benzyl halides
An efficient Hiyama coupling reaction between benzylic halide and aryltrialkoxysilane using Pd nanoparticles has been developed. This procedure accommodates various functional groups to yield a diverse range of diarylmethanes which are ubiquitous units of natural products and pharmaceuticals.
Srimani, Dipankar,Bej, Ansuman,Sarkar, Amitabha
supporting information; experimental part
p. 4296 - 4299
(2010/09/04)

A metal-free catalytic system for the oxidation of benzylic methylenes and primary amines under solvent-free conditions
Iodine-pyridine-tert-butylhydroperoxide is developed as a green and efficient catalytic system for the oxidation of benzylic methylenes to ketones and primary amines to nitriles. The reaction conditions are quite mild and environmentally benign, no transition metals, organic solvents or hazard reagents being needed. The oxidation of benzylic methylenes gave the corresponding ketones in excellent yields with complete chemoselectivity, while the oxidation of primary amines was complete in several minutes, affording various nitriles in moderate to good yields.
Zhang, Jintang,Wang, Zhentao,Wang, Ye,Wan, Changfeng,Zheng, Xiaoqi,Wang, Zhiyong
supporting information; scheme or table
p. 1973 - 1978
(2010/06/15)

Insights into the role of new palladium pincer complexes as robust and recyclable precatalysts for suzuki-miyaura couplings in neat water
Suzuki-Miyaura biaryl and diarylmethane syntheses via the coupling of arylboronic acids with aryl and arylmethyl bromides are performed in water by means of two new CNC-type palladium pincer complexes. Good to excellent results (including high TON values and extended recycling procedures) are obtained in most cases for a range of electronically dissimilar halides and boronic acids. On the basis of a series of kinetics studies, transmission electron microscopy (TEM), mercury drop tests, and quantitative poisoning experiments, the real role of the latter palladacycles, closely linked to the formation and active participation of palladium nanoparticles, is discussed.
Ines, Blanca,Sanmartin, Raul,Moure, Maria Jesus,Dominguez, Esther
experimental part
p. 2124 - 2132
(2009/12/25)

Synthesis of diarylmethane derivatives from Stille cross-coupling reactions of benzylic halides
A catalyst precursor prepared in situ from palladium acetate and a phosphine ligand was used for the Stille cross-coupling reaction of benzylic bromides and chlorides with aryltributyltin analogues. The reactions were performed at 80 °C using dppf as ligand in the presence of KF, or more conveniently using PPh3 in the absence of base, furnishing diarylmethane derivatives in high yields (86-99%). Using Pd(OAc)2/PPh3 as catalyst precursor competitive Stille and Suzuki cross-coupling reactions with benzyl chloride showed that in the absence of base or in the presence of KF the Stille product is the majority product, and only the Suzuki product was obtained in the presence of KOH as base.
Nichele, Tatiana Z.,Monteiro, Adriano L.
p. 7472 - 7475
(2008/03/14)

Simple palladium(II) precatalyst for suzuki-miyaura couplings: Efficient reactions of benzylic, aryl, heteroaryl, and vinyl coupling partners
trans-PdBr(N-Succ)(PPh3)2 (1) is a universally effective precatalyst for Suzuki-Miyaura cross-couplings of benzylic halides with aryl- or heteroarylboronic acids. Substituted aryl halides and halogenated cyclic enones can be cross-coupled with aryl- or vinylboronic acids in excellent yields. Catalyst recycling is also demonstrated.
Burns, Michael J.,Fairlamb, Ian J. S.,Kapdi, Anant R.,Sehnal, Petr,Taylor, Richard J. K.
p. 5397 - 5400
(2008/09/17)

O-benzyl trichloroacetimidates having electron-withdrawing substituents in acid-catalyzed diarylmethane synthesis
Reaction of O-benzyl trichloroacetimidates having electron-withdrawing substituents with arenes in the presence of catalytic amounts of TMSOTf gave the corresponding diarylmethanes in good to excellent yields. Georg Thieme Verlag Stuttgart.
Zhang, Jianjun,Schmidt, Richard R.
p. 1729 - 1733
(2008/02/04)

Kinetics of the solvolyses of benzhydryl derivatives: Basis for the construction of a comprehensive nucleofugality scale
A series of 21 benzhydrylium ions (diarylmethylium ions) are proposed as reference electrofuges for the development of a general nucleofugality scale, where nucleofugality refers to a combination of leaving group and solvent. A total of 167 solvolysis rate constants of benzhydrylium tosylates, bromides, chlorides, trifluoroacetates, 3,5-dinitrobenzoates, and 4-nitroben-zoates, two-thirds of which have been determined during this work, were subjected to a least-squares fit according to the correlation equation log k 25°C = Sf(Nf + Ef), where s f and Nf are nucleofuge-specific parameters and E f is an electrofuge-specific parameter. Although nucleofuges and electrofuges characterized in this way cover more than 12 orders of magnitude, a single set of the parameters, namely sf, Nf, and E f, is sufficient to calculate the solvolysis rate constants at 25°C with an accuracy of ± 16%. Because sf ≈ 1 for all nucleofuges, that is, leaving group/ solvent combinations, studied so far, qualitative discussions of nucleofugality can be based on Nf.
Denegri, Bernard,Streiter, Andre,Juric, Sandra,Ofial, Armin R.,Kronja, Olga,Mayr, Herbert
p. 1648 - 1656
(2007/10/03)

Suzuki-Miyaura cross-coupling of benzylic phosphates with arylboronic acids
(Chemical Equation Presented) Suzuki-Miyaura cross-coupling of benzylic phosphates with arylboronic acids was investigated. Optimum conditions employed the simple catalytic system of palladium(II) acetate (1 mol %) and triphenylphosphine (4 mol %) with either potassium phosphate or potassium carbonate as the base and toluene as the solvent at 90°C. Using the developed conditions, a series of structurally diverse diarylmethanes were prepared.
McLaughlin, Mark
p. 4875 - 4878
(2007/10/03)

Palladium catalyzed ligand-free Suzuki cross-coupling reactions of benzylic halides with aryl boronic acids under mild conditions
A highly efficient Suzuki cross-coupling reaction between benzylic halides and aryl boronic acids using palladium chloride as catalyst in acetone:water (3:1) has been developed. High yields of products, mild reaction conditions and short reaction times in the absence of ligand are important features of this method. A highly efficient Suzuki cross-coupling reaction between benzylic halides and aryl boronic acids using palladium chloride as catalyst in acetone:water (3:1) as the solvent system has been developed. High yields of products, mild reaction conditions and short reaction times in the absence of ligand are important features of this method.
Bandgar,Bettigeri, Sampada V.,Phopase, Jaywant
p. 6959 - 6962
(2007/10/03)

Suzuki cross-coupling reaction of benzylic halides with arylboronic acids in the presence of a tetraphosphine/palladium catalyst
The cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl) cyclopentane-[PdCl(C3H5)]2 system catalyses efficiently the Suzuki cross-coupling reaction of benzylic halides with arylboronic acids. A wide variety of benzylic bromides or chlorides and functionalised arylboronic acids lead selectively to the corresponding diarylmethane adducts in good yields. Furthermore, this catalyst can be used at low loading in many cases.
Chahen, Ludovic,Doucet, Henri,Santelli, Maurice
p. 1668 - 1672
(2007/10/03)

Cross-coupling reactions of potassium alkyltrifluoroborates with aryl and 1-alkenyl trifluoromethanesulfonates.
[figure: see text] The palladium-catalyzed coupling reaction of potassium alkyltrifluoroborates with aryl- or alkenyltriflates proceeds to afford the corresponding arenes or alkenes in high yield. The borates are all solids, stable in air, and thus can be stored on the shelf indefinitely. The cross coupling can be effected using PdCl2(dppf).CH2Cl2 as the catalyst in THF-H2O in the presence of Cs2CO3. A variety of functional groups can be tolerated within the borate and/or the triflate coupling partner.
Molander,Ito
p. 393 - 396
(2007/10/03)

Direct reduction of alcohols: Highly chemoselective reducing system for secondary or tertiary alcohols using chlorodiphenylsilane with a catalytic amount of indium trichloride
The direct reduction of alcohols using chlorodiphenylsilane as A hydride source in the presence of a catalytic amount of indium trichloride is described. Benzylic alcohols, secondary alcohols, and tertiary alcohols were effectively reduced to give the corresponding alkanes in high yields. A compound bearing both primary and secondary hydroxyl groups was reduced only at the secondary site to afford the primary alcohol after workup with Bu4NF. This system showed high chemoselectivity only for the hydroxyl group while not reducing other functional groups that are readily reduced by standard reducing systems. Thus alcohols bearing ester, chloro, bromo, or nitro groups, which are sensitive to LiAlH4 or Zn/H+, were selectively reduced only at the hydroxyl sites by the chlorodiphenylsilane/InCl3 system. NMR studies revealed the reaction course. The hydrodiphenyl-silyl ether is initially formed and then, with InCl3 acting as a Lewis acid, forms an oxonium complex, which accelerates the desiloxylation with donation of the hydrogen to the carbon.
Yasuda,Onishi,Ueba,Miyai,Baba
p. 7741 - 7744
(2007/10/03)

A Study of N-Nitrosoamide-Mediated Friedel-Crafts Type Benzylation of Benzene-Toluene and Benzene-Anisole1a
Nitrogen-separated carbocation-carboxylate ion pairs were employed as sources of carbocations in the alkylation of aromatic compounds. The N-nitrosoamide approach to these nitrogenous-molecule-separated ion pairs is an excellent alternative to the standard acid-catalyzed Friedel-Crafts approach for studies of the alkylation because of the following variables: high reactivity of the electrophile, stability of the products, strict kinetic control, homogeneity, lack of over alkylation, straightforward chemistry, and good product balance. In deaminative benzylations of benzene-toluene and anisole-benzene mixtures, the values of kX/kB and % meta isomer are significantly different from those observed in the standard benzylations in a manner that indicates the deaminative electrophiles are more reactive than those generated by the standard Friedel-Crafts approach. The reactions show a direct proportionality between inter- and intramolecular selectivities and thus follow the Brown selectivity relationship (BSR). The benzylation of 2,4,6-trideuteriotoluene provided no evidence for deuterium rearrangements (or coupled benzyl rearrangements) in the arenium ion intermediate. Kinetic isotope effects were not detected. The methyl substituent on toluene appears to affect intermolecular selectivity (kT/kB) and intramolecular selectivity (o, m, p distribution) to similar degrees. A mechanism is proposed in which both selectivities are determined by activation energy differences in the transition states leading to the σ-complex intermediates. The observation that most standard Friedel-Crafts benzylations do not follow the BSR is discussed in terms of possible systematic errors in those cases. Silver ion-assisted Friedel-Crafts benzylations were performed under dry, basic conditions to investigate whether the standard approach could lead to data that obey the BSR.
Darbeau, Ron W.,White, Emil H.
p. 1121 - 1131
(2007/10/03)

Traceless, solid-phase synthesis of biarylmethane structures through Pd-catalyzed release of supported benzylsulfonium salts
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Vanier, Cecile,Lorge, Franz,Wagner, Alain,Mioskowski, Charles
p. X1679-1683
(2007/10/03)

Novel synthetic usage of indium compounds as catalyst: Reductive deoxygenation of aryl ketones and sec-benzylic alcohols
The combination of chlorodimethylsilane and a catalytic amount of indium compounds is effective for the deoxygenation of aryl ketones and sec-benzylic alcohols to the corresponding hydro- carbons. The combination system is so selective toward carbonyls that the functionalities such as halogen, ester, and ether tolerate the reduction conditions.
Miyai, Takashi,Ueba, Masako,Baba, Akio
p. 182 - 184
(2007/10/03)

A Study of Essentially Free Carbocations Derived via Diazonium and Oxo Diazonium Ions in the Liquid Phase
Nitrogen- and nitrous oxide-separated ion pairs containing 4-substituted benzyl cations and carboxylate or tosylate anions were prepared by thermolysis of N-nitroso- and N-nitroamides, acidification of phenyldiazomethane, and nitrosation of N-benzyl-O-benzoylhydroxylamine. The cations were generated in benzene/toluene and benzene/anisole mixtures and were found to partition between the counterion and the solvent and between the aromatic cosolvent and benzene. A familial relationship among the methods was observed. As the cation became more reactive, the yield of solvent-derived products (SDPs) rose and the ratio of rate constants for its reaction with toluene versus benzene, kT/kB, fell. The yield of SDP also rose as the temperature was decreased and as N2 was replaced by N2O; however, kT/kB remained unchanged. Inert diluents had no effect on kT/kB but decreased hydrocarbon yield by 40% on 2-fold dilution. In the presence of reactive diluents that are converted into secondary alkylating agents, both the % hydrocarbon and kT/kB rose. These results are interpreted in terms of the intermediacy of inert-molecule-separated ion pairs (IMSIPs) in deamination. The cation reacted with benzoates and tosylates not only at the oxygens but also at the ipso carbon; subsequent decarboxylation and desulfonylation, respectively, led to diphenylmethanes. The ester/SDP ratio is introduced as a new measure of carbocation reactivity.
Darbeau, Ron W.,White, Emu H.,Song, Fenhong,Darbeau, Nyla R.,Chou, James
p. 5966 - 5978
(2007/10/03)

Palladium catalyzed cross-coupling between phenyl- or naphthylboronic acids and benzylic bromides
The Suzuki-Miyaura palladium-catalyzed coupling reaction was extended to achieve mixed cross-coupling between substituted aryl and naphthyl mono- and bisbromomethanes with phenylboronic acid, 1-methoxy-2-naphthyl-, 3-methoxy-2-naphthyl-, or 4-methoxy-1-naphthylboronic acid to form the corresponding disubstituted methanes.
Chowdhury, Sultan,Georghiou, Paris E.
p. 7599 - 7603
(2007/10/03)

Palladium-catalyzed coupling reaction of 4-alkylnitrobenzenes with aryl bromides at their benzylic position
4-Alkylnitrobenzenes effectively undergo coupling with aryl bromides at their benzylic position in the presence of a palladium catalyst and a base to give the corresponding mono- and/or di-arylated products in good yields.
Inoh, Jun-Ichi,Satoh, Tetsuya,Pivsa-Art, Sommai,Miura, Masahiro,Nomura, Masakatsu
p. 4673 - 4676
(2007/10/03)

The reactivity-selectivity principle and the electrophilic substitution of aromatic compounds
The application of the Reactivity-Selectivity principle (RSP) to the Friedel-Crafts alkylation reaction has been reinvestigated using the N- nitrosoamide decomposition as the source of electrophiles. Plots of p(f) vs σ+ for 4-methylbenzyl, benzyl, 4-chlorobenzyl, and 4-nitrobenzyl cations] yielded p values of -3.4, -2.5, -2.4, and -1.2, resp. The data indicate that the Reactivity-Selectivity Principle is applicable to the electrophilic substitution of aromatic compounds contrary to a claim in the literature. A claim that a reactivity reversal should occur in Friedel-Crafts benzylation is also shown to be in question.
White, Emil H.
p. 7649 - 7652
(2007/10/03)

A new look at the friedel-crafts alkylation reaction
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White, Emil H.,Darbeau, Ron W.,Chen, Yulong,Chen, Steven,Chen, David
p. 7986 - 7987
(2007/10/03)

One step reduction of diaryl ketones to hydrocarbons by etherated boron trifluoride-triethylsilane system
A convenient one step reduction of diaryl ketones to hydrocarbons using etherated boron trifluoride-triethylsilane is described.
Smonou
p. 1999 - 2002
(2007/10/02)