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Borane-catalyzed C(sp3)-F bond arylation and esterification enabled by transborylation
The activation and functionalization of carbon- fluorine bonds represent a significant synthetic challenge, given the high thermodynamic barrier to C-F bond cleavage. Stoichiometric hydridoborane-mediated C-F functionalization has recently emerged, but is yet to be rendered catalytic. Herein, the borane-catalyzed coupling of alkyl fluorides with arenes (carbon-carbon bond formation) and carboxylic acids (carbon-oxygen bond formation) has been developed using transborylation reactions to achieve catalytic turnover. Successful C-C and C-O coupling across a variety of structurally and electronically differentiated arenes and carboxylic acids was achieved using 9-borabicyclo[3.3.1]nonane (H-B-9-BBN) as the catalyst and pinacolborane (HBpin), with broad functional group tolerance. Experimental and computational studies suggest a mechanistic dichotomy for the carbon-carbon and carbon-oxygen coupling reactions. B-F transborylation (B-F/B-H metathesis) between F-B-9-BBN and HBpin enabled catalytic turnover for carbon-carbon bond formation, whereas direct exchange between the alkyl fluoride and acyloxyboronic ester (C-F/B-O metathesis) was proposed for carbon-oxygen coupling, where H-B-9-BBN catalyzed the dehydrocoupling of the carboxylic acid with HBpin.
Willcox, Dominic R.,Nichol, Gary S.,Thomas, Stephen P.
p. 3190 - 3197
(2021/04/06)

Nitrenium Salts in Lewis Acid Catalysis
Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen-containing compounds are much rarer. Nitrenium cations are a new family of nitrogen-based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents.
Mehta, Meera,Goicoechea, Jose M.
supporting information
p. 2715 - 2719
(2020/01/24)

Phosphonic acid mediated practical dehalogenation and benzylation with benzyl halides
For the first time, by using H3PO3/I2 system, various benzyl chlorides, bromides and iodides were dehalogenated successfully. In the presence of H3PO3, benzyl halides underwent electrophilic substitution reactions with electron-rich arenes, leading to a broad range of diarylmethanes in good yields. These transformations feature green, cheap reducing reagents and metal-free conditions. A possible mechanism was proposed.
Gao, Jing,Han, Li-Biao,Ma, Yonghao,Tang, Zilong,Wu, Xiaofang,Xiao, Jing
p. 22343 - 22347
(2019/07/31)

Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(iii) dication under mild conditions
The readily-accessible, air-stable Lewis acid [(terpy)PPh][B(C6F5)4]21 is shown to mediate the hydrosilylation of aldehydes, ketones, and olefins. The utility and mechanism of these hydrosilylations are considered.
Andrews, Ryan J.,Chitnis, Saurabh S.,Stephan, Douglas W.
supporting information
p. 5599 - 5602
(2019/05/21)

Super electron donor-mediated reductive desulfurization reactions
The desulfurization of thioacetals and thioethers by a pyridine-derived electron donor is described. This methodology provides efficient access to the reduced products in high yields and does not require the use of transition-metals, elemental alkali-metals, or hydrogen atom donors.
Nozawa-Kumada, Kanako,Ito, Shungo,Noguchi, Koto,Shigeno, Masanori,Kondo, Yoshinori
p. 12968 - 12971
(2019/11/05)

An Efficient Ga(OTf)3/Isopropanol Catalytic System for Direct Reduction of Benzylic Alcohols
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
supporting information
p. 4330 - 4335
(2018/10/15)

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)

Feedstocks to Pharmacophores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes Enabling Direct Access to Diarylalkanes
A Cu-catalyzed method has been identified for selective oxidative arylation of benzylic C-H bonds with arylboronic esters. The resulting 1,1-diarylalkanes are accessed directly from inexpensive alkylarenes containing primary and secondary benzylic C-H bonds, such as toluene or ethylbenzene. All catalyst components are commercially available at low cost, and the arylboronic esters are either commercially available or easily accessible from the commercially available boronic acids. The potential utility of these methods in medicinal chemistry applications is highlighted.
Vasilopoulos, Aristidis,Zultanski, Susan L.,Stahl, Shannon S.
p. 7705 - 7708
(2017/06/20)

A Zinc Catalyzed C(sp3)?C(sp2) Suzuki–Miyaura Cross-Coupling Reaction Mediated by Aryl-Zincates
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.
p. 15889 - 15893
(2017/10/24)

Synthetic method of diarylmethanes
The invention discloses a synthetic method of diarylmethanes. The method is characterized in that benzyl pseudohalide and aromatic boric acid are reacted in an organic solvent under alkaline condition. The method employs easily available raw materials, conversion is realized under effect of no transition metal catalysis, water-free and oxygen-free are not required, Lewis acid catalysis is not required, the method has wide substrate universality, and various substituted diarylmethanes can be synthesized by the method.
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Paragraph 0135; 0136; 0137; 0138; 0139

(2017/08/28)

Coupling of arylboronic acids with benzyl halides or mesylates without adding transition metal catalysts
We report herein a transition-metal-free coupling reaction of arylboronic acids with benzyl halides and mesylates for the construction of C(sp2)[sbnd]C(sp3) bonds. A unique feature of this coupling reaction is the formation regioisomers in some cases. Mechanistic studies suggest that this reaction may proceed via an unprecedented Friedel–Crafts-type reaction pathway under base conditions with the assistance of boronic acid moiety.
Wu, Guojiao,Xu, Shuai,Deng, Yifan,Wu, Chaoqiang,Zhao, Xia,Ji, Wenzhi,Zhang, Yan,Wang, Jianbo
p. 8022 - 8030
(2016/11/19)

Ferrocenyl-derived electrophilic phosphonium cations (EPCs) as Lewis acid catalysts
Oxidation of diphenylphosphinoferrocene and 1,1′-bis(diphenylphosphino)ferrocene with XeF2, resulted in the formation of CpFe(η5-C5H4PF2Ph2) 1 and Fe(η5-C5H4PF2Ph2)22 respectively. Subsequent reactions with [SiEt3][B(C6F5)4] yielded [CpFe(η5-C5H4PFPh2)][B(C6F5)4] 3 and [Fe(η5-C5H4PFPh2)2] [B(C6F5)4]24. PhP(η5-C5H4)2Fe 5 was prepared, converted to [PhMeP(η5-C5H4)2Fe][O3SCF3] 6 and then to [PhMeP(η5-C5H4)2Fe][B(C6F5)4] 7. The ability of the salts 3, 4 and 7 to catalyze Friedel-Crafts dimerization of 1,1-diphenylethylene, dehydrocoupling of phenol and triethylsilane, deoxygenation of acetophenone and hydrodefluorination of 1-fluoropentane were probed. While compound 7 proved to be ineffective, compounds 3 and 4 were useful Lewis acid catalysts. Compounds 3 and 4 were shown to catalyze the deoxygenation of a series of ketones.
Mallov, Ian,Stephan, Douglas W.
supporting information
p. 5568 - 5574
(2016/04/09)

Use of Trifluoromethyl Groups for Catalytic Benzylation and Alkylation with Subsequent Hydrodefluorination
The electrophilic organofluorophosphonium catalyst [(C6F5)3PF][B(C6F5)4] is shown to effect benzylation or alkylation by aryl and alkyl CF3 groups with subsequent hydrodefluorination, thus resulting in a net transformation of CF3 into CH2-aryl fragments. In the case of alkyl CF3 groups, Friedel-Crafts alkylation by the difluorocarbocation proceeded without cation rearrangement, in contrast to the corresponding reactions of alkyl monofluorides.
Zhu, Jiangtao,Prez, Manuel,Caputo, Christopher B.,Stephan, Douglas W.
supporting information
p. 1417 - 1421
(2016/02/14)

Synthesis and catalytic reactivity of mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes
The reactions of five dinuclear carbonyl complexes [(η 5-C5Me4R)Mo(CO)3]2 [R = allyl, n Bu, t Bu, Ph, Bz] with I2 in chloroform solution gave the corresponding mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes [(η 5-C5Me4R)MoI(CO)3] [R = allyl (1), n Bu (2), t Bu (3), Ph (4), Bz (5)]. The molecular structures of complexes 2, 3 and 5 were determined by X-ray diffraction analysis. The results show that the substituent in the ring can directly affect the Mo-I bond distances; the more sterically hindered the substituent, the longer the Mo-I bond. Friedel-Crafts reactions of aromatic compounds with a variety of alkylation reagents catalyzed by the complexes showed that all of these mononuclear molybdenum carbonyl complexes have catalytic activity in Friedel-Crafts alkylation reactions. Indeed, compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as higher activities, mild reaction conditions, high selectivity, simple post-processing, and environmentally friendly chemistry.
Ma, Zhi-Hong,Lv, Lin-Qian,Wang, Hong,Han, Zhan-Gang,Zheng, Xue-Zhong,Lin, Jin
p. 225 - 233
(2016/02/20)

Ethers as hydrogen sources in BF3·OEt2 promoted reduction of diphenylmethyl alcohols, ethers and esters to hydrocarbons
A novel ether/BF3 reductive system has been described, in which diphenylmethanols and their ether and ester derivatives are used as starting materials. Reductions are performed in ether under reflux and an argon atmosphere, and the addition of extra water is beneficial to this reduction. A series of alkanes are able to be prepared with good to excellent yields. A deuterated experiment exhibits that the reductive hydrogen is generated from ether. The mechanism is discussed in detail to explain the observed reactivity.
Li, Jiaqiang,Liu, Qing,Shen, Hang,Huang, Ruofeng,Zhang, Xiaohui,Xiong, Yan,Chen, Changguo
p. 85291 - 85295
(2015/11/02)

Discovery of 1,1′-Biphenyl-4-sulfonamides as a New Class of Potent and Selective Carbonic Anhydrase XIV Inhibitors
New 1,1′-biphenylsulfonamides were synthesized and evaluated as inhibitors of the ubiquitous human carbonic anhydrase isoforms I, II, IX, XII, and XIV using acetazolamide (AAZ) as reference compound. The sulfonamides 1-21 inhibited all the isoforms, with Ki values in the nanomolar range of concentration, and were superior to AAZ against all of them. X-ray crystallography and molecular modeling studies on the adducts that compound 20, the most potent hCA XIV inhibitor of the series (Ki = 0.26 nM), formed with the five hCAs, provided insight into the molecular determinants responsible for the high affinity of this molecule toward the target enzymes. The results pave the way to the development of 1.1′-biphenylsulfonamides as a new class of highy potent hCA XIV inhibitors.
La Regina, Giuseppe,Coluccia, Antonio,Famiglini, Valeria,Pelliccia, Sveva,Monti, Ludovica,Vullo, Daniela,Nuti, Elisa,Alterio, Vincenzo,De Simone, Giuseppina,Monti, Simona Maria,Pan, Peiwen,Parkkila, Seppo,Supuran, Claudiu T.,Rossello, Armando,Silvestri, Romano
supporting information
p. 8564 - 8572
(2015/11/24)

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations
Ketones are efficiently deoxygenated in the presence of silane using highly electrophilic phosphonium cation (EPC) salts as catalysts, thus affording the corresponding alkane and siloxane. The influence of distinct substitution patterns on the catalytic effectiveness of several EPCs was evaluated. The deoxygenation mechanism was probed by DFT methods.
Mehta, Meera,Holthausen, Michael H.,Mallov, Ian,Pérez, Manuel,Qu, Zheng-Wang,Grimme, Stefan,Stephan, Douglas W.
supporting information
p. 8250 - 8254
(2015/07/07)

Facile Protocol for Catalytic Frustrated Lewis Pair Hydrogenation and Reductive Deoxygenation of Ketones and Aldehydes
A series of ketones and aldehydes are reduced in toluene under H2 in the presence of 5 mol % B(C6F5)3 and either cyclodextrin or molecular sieves affording a facile metal-free protocol for reduction to alcohols. Similar treatment of aryl ketones resulted in metal-free deoxygenation yielding aromatic hydrocarbons.
Mahdi, Tayseer,Stephan, Douglas W.
p. 8511 - 8514
(2015/11/27)

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)

Iron catalysed Negishi cross-coupling using simple ethyl-monophosphines
Monophosphines prepared by iron catalysed hydrophosphination have been used as pro-ligands in iron catalysed Negishi cross-coupling of alkyl bromides and diphenyl zinc reagents. The cross-coupling has been investigated with monophosphines with varying electronic properties and we find the simplest, unsubstituted phosphine to offer the optimum reaction conditions (both in terms of yield of diarylmethane product and cost-effectiveness of the phosphine). In situ catalyst generation from monophosphine and FeCl2 was used in catalysis; however, preparation of a discrete homonuclear iron complex was also achieved and this four-coordinate iron-phosphine complex was isolated and used in catalysis.
Brown, Caleb A.,Nile, Terence A.,Mahon, Mary F.,Webster, Ruth L.
p. 12189 - 12195
(2016/01/15)

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)

Alternative approach toward the generation of benzylic zinc reagent: Direct oxidative addition of active zinc into the carbon-oxygen bond of benzyl mesylates
The use of highly active zinc, prepared by the Rieke method, for the direct preparation of benzylic zinc mesylate was investigated. The oxidative addition of highly active zinc to benzyl mesylate was easily completed under mild conditions. The resulting benzylic zinc mesylates were employed in subsequent cross-coupling reactions with a broad range of electrophiles, and the formation of the corresponding products was successful.
Jung, Hye-Soo,Kim, Seung-Hoi
p. 666 - 670
(2015/03/14)

Flow chemistry as a discovery tool to access sp2-sp3 cross-coupling reactions via diazo compounds
The work takes advantage of an important feature of flow chemistry, whereby the generation of a transient species (or reactive intermediate) can be followed by a transfer step into another chemical environment, before the intermediate is reacted with a coupling partner. This concept is successfully applied to achieve a room temperature sp2-sp3 cross coupling of boronic acids with diazo compounds, these latter species being generated from hydrazones under flow conditions using MnO2 as the oxidant.
Tran, Duc N.,Battilocchio, Claudio,Lou, Shing-Bong,Hawkins, Joel M.,Ley, Steven V.
p. 1120 - 1125
(2015/03/04)

Unsymmetrical diarylmethanes by ferroceniumboronic acid catalyzed direct friedel-crafts reactions with deactivated benzylic alcohols: Enhanced reactivity due to ion-pairing effects
The development of general and more atom-economical catalytic processes for Friedel-Crafts alkylations of unactivated arenes is an important objective of interest for the production of pharmaceuticals and commodity chemicals. Ferroceniumboronic acid hexafluoroantimonate salt (1) was identified as a superior air- and moisture-tolerant catalyst for direct Friedel-Crafts alkylations of a variety of slightly activated and neutral arenes with stable and readily available primary and secondary benzylic alcohols. Compared to the use of classical metal-catalyzed alkylations with toxic benzylic halides, this methodology employs exceptionally mild conditions to provide a wide variety of unsymmetrical diarylmethanes and other 1,1-diarylalkane products in high yield with good to high regioselectivity. The optimal method, using the bench-stable ferroceniumboronic acid salt 1 in hexafluoroisopropanol as cosolvent, displays a broader scope compared to previously reported catalysts for similar Friedel-Crafts reactions of benzylic alcohols, including other boronic acids such as 2,3,4,5-tetrafluorophenylboronic acid. The efficacy of the new boronic acid catalyst was confirmed by its ability to activate primary benzylic alcohols functionalized with destabilizing electron-withdrawing groups like halides, carboxyesters, and nitro substituents. Arene benzylation was demonstrated on a gram scale at up to 1 M concentration with catalyst recovery. Mechanistic studies point toward the importance of the ionic nature of the catalyst and suggest that factors other than the Lewis acidity (pKa) of the boronic acid are at play. A SN1 mechanism is proposed where ion exchange within the initial boronate anion affords a more reactive carbocation paired with the non-nucleophilic hexafluoroantimonate counteranion.
Mo, Xiaobin,Yakiwchuk, Joshua,Dansereau, Julien,Adam McCubbin,Hall, Dennis G.
supporting information
p. 9694 - 9703
(2015/08/18)

Iron-catalyzed hetero-cross-dehydrogenative coupling reactions of sulfoximines with diarylmethanes: A new route to N-alkylated sulfoximines
An efficient iron-catalyzed C-N bond formation by hetero-cross- dehydrogenative coupling (CDC) between sulfoximines and diarylmethanes is described. The reaction shows good functional group tolerance and provides N-alkylated sulfoximines in moderate to go
Cheng, Ying,Dong, Wanrong,Wang, Long,Parthasarathy, Kanniyappan,Bolm, Carsten
supporting information
p. 2000 - 2002
(2014/05/06)

Synthesis of structurally diverse diarylketones through the diarylmethyl sp3 C-H oxidation
Under open-flask conditions, an efficient method to assemble a series of diversely functionalized diarylketones in the presence of commercially available NBS has been developed. Yields of up to 99% have been achieved employing diarylmethanes as starting material. Based on 18O-labeled experiment, the addition of stoichiometric water eventually leads to excellent yields in all carbonylation cases.
He, Chao,Zhang, Xiaohui,Huang, Ruofeng,Pan, Jing,Li, Jiaqiang,Ling, Xuege,Xiong, Yan,Zhu, Xiangming
supporting information
p. 4458 - 4462
(2014/08/05)

Threefold and chemoselective couplings of triarylbismuths with benzylic chlorides and iodides using palladium catalysis
This paper describes the palladium-catalyzed studies on threefold coupling of triarylbismuth reagents with benzylic chlorides and iodides. The optimized protocol conditions are operationally simple, delivering threefold coupling of a variety of triarylbismuths in combination with benzylic chlorides and iodides. The two optimized protocols allowed the synthesis of a diverse range of unsymmetrical diarylmethanes in an efficient manner. As part of this study, chemoselective transformation of benzylic chlorides and iodides was also achieved. This journal is the Partner Organisations 2014.
Rao, Maddali L. N.,Dhanorkar, Ritesh J.
p. 13134 - 13144
(2014/04/03)

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)

Pd-catalyzed chemoselective threefold cross-coupling of triarylbismuths with benzylic bromides
An efficient palladium-catalyzed protocol was demonstrated for the chemoselective cross-coupling of functionalized benzylic bromides with triarylbismuth reagents. Under the established conditions, catalyzed by palladium in the presence of K3PO
Rao, Maddali L. N.,Dhanorkar, Ritesh J.
p. 6794 - 6798
(2013/05/23)

Simplifying iron-phosphine catalysts for cross-coupling reactions
Any old iron? Iron catalysts based on the widely available diphosphine ligand bis(diphenylphosphino)ethane have not previously fared particularly well in iron-catalyzed cross-coupling processes. However, this turns out not to be due to any inherently poor performance associated with the ligand, but rather the need to form a bis-chelate complex, either before or during the formation of an active FeI species. Copyright
Bedford, Robin B.,Carter, Emma,Cogswell, Paul M.,Gower, Nicholas J.,Haddow, Mairi F.,Harvey, Jeremy N.,Murphy, Damien M.,Neeve, Emily C.,Nunn, Joshua
supporting information
p. 1285 - 1288
(2013/03/13)

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)

Efficient synthesis of substituted styrenes and biaryls (or heteroaryls) with regioselective reactions of ortho -, meta -, and para-bromobenzyl bromide
Regio- and stereoselective reactions of ortho-, meta-, and para-bromobenzyl bromide under Stille and (or) Suzuki cross-coupling reactions are described that provided substituted styrene monomers and biaryls in two steps. By controlling the experimental conditions, the first coupling provided access to allylarene or diarylmethane intermediates, and the second reaction led to the desired styrenes and biaryls, substituted by a spacer arm in the ortho, meta or para position depending on the starting material. Georg Thieme Verlag Stuttgart · New York.
Anselmi, Elsa,Abarbri, Mohamed,Duchene, Alain,Langle-Lamande, Sandrine,Thibonnet, Jerome
experimental part
p. 2023 - 2040
(2012/09/05)

Exploiting boron-zinc transmetallation for the arylation of benzyl halides: What are the reactive species?
One step Beyond: The transmetallation reactions of ArB(OH)2 and Ar3B3O3 with Et2Zn are far more complicated than previously supposed, with solvent-dependent equilibria between ArB(OY)2 at one side and [RZn(solv)3][BR4] at the other (see picture). While the role of the highly reactive organozinc cation has not been implicated before, its importance for the activation of an otherwise sluggish class of electrophiles is shown. Copyright
Bedford, Robin B.,Gower, Nicholas J.,Haddow, Mairi F.,Harvey, Jeremy N.,Nunn, Joshua,Okopie, Rukeme A.,Sankey, Rosalind F.
supporting information; experimental part
p. 5435 - 5438
(2012/07/03)

InBr3-catalyzed deoxygenation of carboxylic acids with a hydrosilane: Reductive conversion of aliphatic or aromatic carboxylic acids to primary alcohols or diphenylmethanes
A simple and practical procedure for the direct reduction of aliphatic carboxylic acids with a variety of functional groups to a primary alcohol using the mild reducing reagent tetramethyldisiloxane (TMDS), in the presence of a catalytic amount of InBr3 has been developed. This simple reducing system, when used together with a hydrosilane, allows the preparation of the diphenylmethane derivative directly from an aromatic carboxylic acid and an aromatic compound. Copyright
Sakai, Norio,Kawana, Keita,Ikeda, Reiko,Nakaike, Yumi,Konakahara, Takeo
experimental part
p. 3178 - 3183
(2011/06/28)

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)

Nickel boride-mediated cleavage of 1,3-dithiolanes: A convenient approach to reductive desulfurization
1,3-Dithiolanes are rapidly cleaved by nickel boride, generating corresponding hydrocarbons in excellent yields. The hydrogenolysis is rapid at room temperature and does not require protection from the atmosphere. Mild reaction conditions, simple workup, and good yields of pure products are some of the major advantages of the procedure.
Khurana, Jitender M.,Magoo, Devanshi
experimental part
p. 2908 - 2913
(2010/10/19)

Extremely efficient cross-coupling of benzylic halides with aryltitanium tris(isopropoxide) catalyzed by low loadings of a simple palladium(II) acctate/Tris(p-tolyl)phosphine system
Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O-i-Pr)3] catalyzed by a simple palladium(II) Acctate/tris(p-tolyl)phosphine [Pd(OAc)2/ P(p-tolyl)3] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2 mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electronwithdrawing cyano (CN) or trifluoromethyl (CF 3) substituents, the reactions require a higher catalyst loading of 1 mol%, or the reactions are carried out at 60°C. The catalytic system also tolerates (1-bromoethyl)benzene bearing β-hydrogen atoms while using a catalyst loading of 1 mol% to afford the coupling product in a 70% yield.
Chen, Chi-Ren,Zhou, Shuangliu,Biradar, Deepak Baburao,Gau, Han-Mou
experimental part
p. 1718 - 1727
(2010/09/18)

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)

Simple mixed Fe-Zn catalysts for the Suzuki couplings of tetraarylborates with benzyl halides and 2-halopyridines
Employing co-catalytic zinc reagents facilitates the iron-catalysed Suzuki cross-coupling of tetraarylborates with both benzyl and 2-heteroaryl halides.
Bedford, Robin B.,Hall, Mark A.,Hodges, George R.,Huwe, Michael,Wilkinson, Mark C.
supporting information; experimental part
p. 6430 - 6432
(2010/03/03)

TETRACYCLIC INHIBITORS OF FATTY ACID AMIDE HYDROLASE
Certain tetracyclic compounds are described, which may be used in pharmaceutical compositions and methods for treating disease states, disorders, and conditions mediated by fatty acid amide hydrolase (FAAH) activity. Thus, the compounds may be administered to treat, e.g., anxiety, pain, inflammation, sleep disorders, eating disorders, or movement disorders (such as multiple sclerosis).
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(2009/01/20)

An efficient synthesis of unsymmetrical diarylmethanes from the dehydration of arenes with benzyl alcohols using InCl3·4H2O/acetylacetone catalyst system
An efficient and practical synthesis of unsymmetrical diarylmethanes has been achieved from the dehydration of arenes with benzyl alcohols in the presence of catalytic amount of InCl3·4H2O/acetylacetone.
Sun, Hong-Bin,Li, Biao,Chen, Songjie,Li, Jie,Hua, Ruimao
p. 10185 - 10188
(2008/02/13)

Structure-activity relationships of α-ketooxazole inhibitors of fatty acid amide hydrolase
A systematic study of the structure-activity relationships of 2b (OL-135), a potent inhibitor of fatty acid amide hydrolase (FAAH), is detailed targeting the C2 acyl side chain. A series of aryl replacements or substituents for the terminal phenyl group provided effective inhibitors (e.g., 5c, aryl = 1-napthyl, K, - 2.6 nM), with 5hh (aryl -3-ClPh, Ki = 900 pM) being 5-fold more potent than 2b. Conformationally restricted C2 side chains were examined, and many provided exceptionally potent inhibitors, of which 11j (ethylbiphenyl side chain) was established to be a 750 pM inhibitor. A systematic series of heteroatoms (O, NMe, S), electron-withdrawing groups (SO, SO2), and amides positioned within and hydroxyl substitutions on the linking side chain were investigated, which typically led to a loss in potency. The most tolerant positions provided effective inhibitors (12p, 6-position S, Ki = 3 nM, or 13d, 2-position OH, Ki = 8 nM) comparable in potency to 2b. Proteome-wide screening of selected inhibitors from the systematic series of >100 candidates prepared revealed that they are selective for FAAH over all other mammalian serine proteases.
Hardouin, Christophe,Kelso, Michael J.,Romero, F. Anthony,Rayl, Thomas J.,Leung, Donmienne,Hwang, Inkyu,Cravatt, Benjamin F.,Boger, Dale L.
p. 3359 - 3368
(2008/02/13)

Thermally generated phenylcarbenium ions: acid-free and self-quenching Friedel-Crafts reactions
2-Benzyloxy-1-methylpyridinium triflate (1) serves as a stable precursor to a phenylcarbenium species as evidenced by its reactivity in Friedel-Crafts alkylations with electron-rich arenes.
Albiniak, Philip A.,Dudley, Gregory B.
p. 8097 - 8100
(2008/03/13)

Efficient and selective alkylation of arenes and heteroarenes with benzyl and allyl ethers using a Ir/Sn bimetallic catalyst
A high-valent heterobimetallic catalyst namely [Ir2(COD)2(SnCl3)2(Cl)2(μ-Cl)2] (5 mol %), or dual catalyst system of [Ir(COD)Cl]2 (1 mol %) and SnCl4 (4 mol %), promotes the benzylation or allylation of arenes and heteroarenes using ethers as the alkylating agents. An electrophilic mechanism is proposed from a Hammett correlation.
Podder, Susmita,Roy, Sujit
p. 9146 - 9152
(2008/02/09)

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)

Selective double Suzuki cross-coupling reactions. Synthesis of unsymmetrical diaryl (or heteroaryl) methanes
Using a double Suzuki cross-coupling reaction ortho- or para-bromobenzyl bromides are easily transformed into unsymmetrical diaryl (or heteroaryl) methanes.
Langle, Sandrine,Abarbri, Mohamed,Duchêne, Alain
p. 9255 - 9258
(2007/10/03)

Hypophosphorous acid-iodine: A novel reducing system. Part 2: Reduction of benzhydrols to diarylmethylene derivatives
A mixture of hypophosphorous acid (H3PO2) and iodine in acetic acid reduces a variety of substituted benzhydrols to the corresponding methylene derivatives in very high yields. The active reducing agent is hydrogen iodide generated by reaction between iodine and hypophosphorous acid.
Gordon, Paul E.,Fry, Albert J.
p. 831 - 833
(2007/10/03)

A study of hydrogenation of benzhydrols in the presence of catalytic amount of triflic acid
The ionic hydrogenation of diarylcarbinols by triethylsilane, in the presence of catalytic amount of triflic acid proceeds via dibenzhydryl ethers. These ethers do not disproportionate to benzophenones and diphenylmethanes but are reduced by triethylsilane to diarylmethanes.
Waterlot,Couturier,De Backer,Rigo
p. 1242 - 1246
(2007/10/03)

Hypophosphorous acid-iodine: A novel reducing system. Part 1: Reduction of diaryl ketones to diaryl methylene derivatives
A mixture of hypophosphorous acid (H3PO2) and iodine in hot acetic acid reduces diaryl ketones quickly and aryl alkyl ketones slowly to the corresponding methylene derivatives. The active reducing agent is hydrogen iodide, generated by reaction between iodine and hypophosphorous acid. (C) 2000 Elsevier Science Ltd.
Hicks,Han,Fry
p. 7817 - 7820
(2007/10/03)