- Structure and reactivity in neutral organic electron donors derived from 4-dimethylaminopyridine
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The effects on the redox properties of modifying the molecular skeleton of neutral bis-2-(4-dimethylamino)pyridinylidene electron donors, derived from 4-dimethylaminopyridine (4-DMAP), have been explored, by varying two parameters: (i) the length of a polymethylene chain linking the two pyridine-derived rings and (ii) the nature of the nitrogen substituents on the 4 and 4″ positions of the precursor pyridines. Restricting the bridge length to two methylene units significantly altered the redox profile, while changes in the nitrogen-substituents at the 4 and 4' positions led to only slight changes in the redox potentials.
- Garnier, Jean,Kennedy, Alan R.,Berlouis, Leonard E. A.,Murphy, John A.,Turner, Andrew T.
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- Photochemical Decarboxylative C(sp3)-X Coupling Facilitated by Weak Interaction of N-Heterocyclic Carbene
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While N-hydroxyphthalimide (NHPI) ester has emerged as a powerful reagent as an alkyl radical source for a variety of C-C bond formations, the corresponding C(sp3)-N bond formation is still in its infancy. We demonstrate herein transition-metal-free decarboxylative C(sp3)-X bond formation enabled by the photochemical activity of the NHPI ester-NaI-NHC complex, giving primary C(sp3)-(N)phth, secondary C(sp3)-I, or tertiary C(sp3)-(meta C)phth coupling products. The primary C(sp3)-(N)phth coupling offers convenient access to primary amines.
- Chen, Kun-Quan,Wang, Zhi-Xiang,Chen, Xiang-Yu
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supporting information
p. 8059 - 8064
(2020/11/02)
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- Base-Mediated O-Arylation of Alcohols and Phenols by Triarylsulfonium Triflates
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A mild and efficient protocol for O-arylation of alcohols and phenols (ROH) by triarylsulfonium triflates was developed under transition-metal-free conditions. Various alcohols, including primary, secondary and tertiary, and phenols bearing either electron-donating or electron-withdrawing groups on the aryl rings were smoothly converted to form the corresponding aromatic ethers in moderate to excellent yields. The reactions were conducted at 50 or 80 °C for 24 h in the presence of a certain base and showed good functional group tolerance. The base-mediated arylation with asymmetric triarylsulfonium salts could selectively transfer the aryl groups of sulfoniums to ROH, depending on their inherent electronic nature. The mechanistic studies revealed that the reaction might proceed through the nucleophilic attack of the in situ formed alkoxy or phenoxy anions at the aromatic carbon atoms of the C?S bonds of triarylsulfonium cations to furnish the target products.
- Ming, Xiao-Xia,Tian, Ze-Yu,Zhang, Cheng-Pan
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supporting information
p. 3370 - 3379
(2019/11/03)
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- Systematic Evaluation of 2-Arylazocarboxylates and 2-Arylazocarboxamides as Mitsunobu Reagents
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2-Arylazocarboxylate and 2-arylazocarboxamide derivatives can serve as replacements of typical Mitsunobu reagents such as diethyl azodicarboxylate. A systematic investigation of the reactivity and physical properties of those azo compounds has revealed that they have an excellent ability as Mitsunobu reagents. These reagents show similar or superior reactivity as compared to the known azo reagents and are applicable to the broad scope of substrates. pKa and steric effects of substrates have been investigated, and the limitation of the Mitsunobu reaction can be overcome by choosing suitable reagents from the library of 2-arylazocarboxylate and 2-aryl azocarboxamide derivatives. Convenient recovery of azo reagents is available by one-pot iron-catalyzed aerobic oxidation, for example. SC-DSC analysis of representative 2-arylazocarboxylate and 2-arylazocarboxamide derivatives has shown high thermal stability, indicating that these azo reagents possess lower chemical hazard compared with typical azo reagents.
- Hirose, Daisuke,Gazvoda, Martin,Ko?mrlj, Janez,Taniguchi, Tsuyoshi
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p. 4712 - 4729
(2018/04/26)
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- Metal-Free I2-Catalyzed Highly Selective Dehydrogenative Coupling of Alcohols and Cyclohexenones
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The I2 catalyzed highly selective oxidative condensation of cyclohexenones and alcohols for the synthesis of aryl alkyl ethers has been described. DMSO is employed as the mild terminal oxidant. This novel methodology offers a metal-free reaction condition, operational simplicity and broad substrate scope to afford valuable products from inexpensive reagents. Various meta-substituted aromatic ethers which are hardly synthesized from the reported methods requiring meta-substituted phenols, are efficiently prepared by the present protocol.
- Liang, Yu-Feng,Yuan, Yizhi,Shen, Tao,Song, Song,Jiao, Ning
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p. 233 - 240
(2018/02/19)
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- Base-Free Generation of Organic Electron Donors from Air-Stable Precursors
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Organic electron donors (OEDs) are powerful reducing agents recognized for their potential in the reduction of challenging substrates and in original applications. Nonetheless, their low stability in atmospheric oxygen or over time complicates their manipulation and storage. To overcome these constraints and enhance OED practicality, new air- and moisture-stable aminopyridinium carboxylate and carbonate precursors were synthesized and thermally activated to generate the potent electron donor in situ. Carboxylate adducts proved to be excellent latent OED systems, enabling the facile and efficient reduction of challenging substrates. Their reduction properties were correlated to their structural characteristics by thermogravimetric and spectroscopic analysis.
- Tintori, Guillaume,Nabokoff, Pierre,Buhaibeh, Ruqaya,Bergé-Lefranc, David,Redon, Sébastien,Broggi, Julie,Vanelle, Patrice
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supporting information
p. 3148 - 3153
(2018/03/13)
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- Manganese-Mediated C?H Alkylation of Unbiased Arenes Using Alkylboronic Acids
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The alkylation of arenes is an essential synthetic step of interest not only from the academic point of view but also in the bulk chemical industry. Despite its limitations, the Friedel–Crafts reaction is still the method of choice for most of the arene alkylation processes. Thus, the development of new strategies to synthesize alkyl arenes is a highly desirable goal, and herein, we present an alternative method to those conventional reactions. Particularly, a simple protocol for the direct C?H alkylation of unbiased arenes with alkylboronic acids in the presence of Mn(OAc)3?2H2O is reported. Primary or secondary unactivated alkylboronic acids served as alkylating agents for the direct functionalization of representative polyaromatic hydrocarbons (PAHs) or benzene. The results are consistent with a free-radical mechanism.
- Castro, Susana,Fernández, Juan J.,Fa?anás, Francisco J.,Vicente, Rubén,Rodríguez, Félix
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supporting information
p. 9068 - 9071
(2016/07/14)
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- Pushing the Limits of Neutral Organic Electron Donors: A Tetra(iminophosphorano)-Substituted Bispyridinylidene
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A new ground-state organic electron donor has been prepared that features four strongly π-donating iminophosphorano substituents on a bispyridinylidene skeleton. Cyclic voltammetry reveals a record redox potential of ?1.70 V vs. saturated calomel electrode (SCE) for the couple involving the neutral organic donor and its dication. This highly reducing organic compound can be isolated (44 %) or more conveniently generated in situ by a deprotonation reaction involving its readily prepared pyridinium ion precursor. This donor is able to reduce a variety of aryl halides, and, owing to its redox potential, was found to be the first organic donor to be effective in the thermally induced reductive S N bond cleavage of N,N-dialkylsulfonamides, and reductive hydrodecyanation of malonitriles.
- Hanson, Samuel S.,Doni, Eswararao,Traboulsee, Kyle T.,Coulthard, Graeme,Murphy, John A.,Dyker, C. Adam
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p. 11236 - 11239
(2016/07/06)
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- From insertion to multicomponent coupling: Temperature dependent reactions of arynes with aliphatic alcohols
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The temperature dependent selectivity switch in the reaction of arynes with aliphatic alcohols in THF has been reported. At -20°C, arynes smoothly insert into the O-H bond of alcohols to form alkyl aryl ethers. Interestingly, at 60°C, a highly selective multicomponent coupling occurs with the solvent THF acting as the nucleophilic trigger affording (4-(alkoxy)butoxy)arenes.
- Thangaraj, Manikandan,Bhojgude, Sachin Suresh,Mane, Manoj V.,Biju, Akkattu T.
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supporting information
p. 1665 - 1668
(2016/01/30)
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- Advances and mechanistic insight on the catalytic Mitsunobu reaction using recyclable azo reagents
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Ethyl 2-arylhydrazinecarboxylates can work as organocatalysts for Mitsunobu reactions because they provide ethyl 2-arylazocarboxylates through aerobic oxidation with a catalytic amount of iron phthalocyanine. First, ethyl 2-(3,4-dichlorophenyl)hydrazinecarboxylate has been identified as a potent catalyst, and the reactivity of the catalytic Mitsunobu reaction was improved through strict optimization of the reaction conditions. Investigation of the catalytic properties of ethyl 2-arylhydrazinecarboxylates and the corresponding azo forms led us to the discovery of a new catalyst, ethyl 2-(4-cyanophenyl)hydrazinecarboxylates, which expanded the scope of substrates. The mechanistic study of the Mitsunobu reaction with these new reagents strongly suggested the formation of betaine intermediates as in typical Mitsunobu reactions. The use of atmospheric oxygen as a sacrificial oxidative agent along with the iron catalyst is convenient and safe from the viewpoint of green chemistry. In addition, thermal analysis of the developed Mitsunobu reagents supports sufficient thermal stability compared with typical azo reagents such as diethyl azodicarboxylate (DEAD). The catalytic system realizes a substantial improvement of the Mitsunobu reaction and will be applicable to practical synthesis.
- Hirose, Daisuke,Gazvoda, Martin,Ko?mrlj, Janez,Taniguchi, Tsuyoshi
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p. 5148 - 5159
(2016/07/29)
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- Synthesis of Ethers via Reaction of Carbanions and Monoperoxyacetals
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Although transfer of electrophilic alkoxyl ("RO+") from organic peroxides to organometallics offers a complement to traditional methods for etherification, application has been limited by constraints associated with peroxide reactivity and stability. We now demonstrate that readily prepared tetrahydropyranyl monoperoxyacetals react with sp3 and sp2 organolithium and organomagnesium reagents to furnish moderate to high yields of ethers. The method is successfully applied to the synthesis of alkyl, alkenyl, aryl, heteroaryl, and cyclopropyl ethers, mixed O,O-acetals, and S,S,O-orthoesters. In contrast to reactions of dialkyl and alkyl/silyl peroxides, the displacements of monoperoxyacetals provide no evidence for alkoxy radical intermediates. At the same time, the high yields observed for transfer of primary, secondary, or tertiary alkoxides, the latter involving attack on neopentyl oxygen, are inconsistent with an SN2 mechanism. Theoretical studies suggest a mechanism involving Lewis acid promoted insertion of organometallics into the O-O bond.
- Kyasa, ShivaKumar,Meier, Rebecca N.,Pardini, Ruth A.,Truttmann, Tristan K.,Kuwata, Keith T.,Dussault, Patrick H.
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p. 12100 - 12114
(2016/01/09)
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- Cross-coupling of nonactivated primary and secondary alkyl halides with aryl Grignard reagents catalyzed by chiral iron pincer complexes
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Iron(III) bisoxazolinylphenylamido (bopa) pincer complexes are efficient precatalysts for the cross-coupling of nonactivated primary and secondary alkyl halides with phenyl Grignard reagents. The reactions proceed at room temperature in moderate to excellent yields. A variety of functional groups can be tolerated. The enantioselectivity of the coupling of secondary alkyl halides is low.
- Bauer, Gerald,Cheung, Chi Wai,Hu, Xile
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p. 1726 - 1732
(2015/06/16)
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- Copper-catalyzed O-arylation of N-protected 1,2-aminoalcohols using functionalized trivalent organobismuth reagents
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The O-arylation of 1,2-aminoalcohols using functionalized triarylbismuth reagents is reported. The reaction can be performed using substoichiometric amounts of copper acetate and operates under mild conditions. Good functional group tolerance is observed, giving access to a range of β-aryloxyamines. The effect provided by the amino group in the arylation reaction is investigated.
- Petiot, Pauline,Dansereau, Julien,Hbert, Martin,Khene, Imene,Ahmad, Tabinda,Samaali, Samira,Leroy, Maxime,Pinsonneault, Francis,Legault, Claude Y.,Gagnon, Alexandre
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supporting information
p. 1322 - 1327
(2015/01/30)
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- Suzuki-miyaura cross-coupling reactions of unactivated alkyl halides catalyzed by a nickel pincer complex
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A nickel(II) pincer complex, [(MeN2N)Ni-Cl], was used to catalyze alkyl-alkyl and alkyl-aryl Suzuki-Miyaura coupling reactions of unactivated alkyl halides. The coupling of 9-alkyl-9-borabicyclo[3.3.1]nonane and 9-phenyl-9-borabicyclo[3.3.1]nonane reagents with alkyl halides was achieved in modest to good yields. The reactions tolerated a variety of useful functional groups including ester, ether, furan, thioether, acetal, and Boc groups. Georg Thieme Verlag Stuttgart, New York.
- Di Franco, Thomas,Boutin, Nicolas,Hu, Xile
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p. 2949 - 2958
(2013/11/06)
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- Recyclable mitsunobu reagents: Catalytic mitsunobu reactions with an iron catalyst and atmospheric oxygen
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Aerobic recycling: A catalytic amount of a hydrazine reagent is sufficient to promote Mitsunobu reactions in the presence of triphenylphosphine, an iron catalyst, and air. The active form of the catalyst, an azo species, can be readily generated by iron-c
- Hirose, Daisuke,Taniguchi, Tsuyoshi,Ishibashi, Hiroyuki
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supporting information
p. 4613 - 4617
(2013/06/04)
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- A novel organic electron donor derived from N-methylisatin
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We report the reactivity of an electron donor derived from N-methylisatin on reduction by sodium amalgam. Transfer of a clear supernatant solution to iodoarenes affords the products of two-electron reduction. Reductions of sulfones, activated arenesulfonamides, and Weinreb amides are also reported.
- Sword, Ryan,O'Sullivan, Steven,Murphy, John A.
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p. 314 - 322
(2013/05/08)
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- One-pot sequential synthesis of ethers from an aliphatic carboxylic acid and an alcohol by indium-catalyzed deoxygenation of an ester
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We have developed a widely applicable and direct method of etherification from a carboxylic acid and an alcohol by indium-catalyzed deoxygenation of the transient ester formed in a one-pot reaction. This simple catalytic reducing system appears to be remarkably tolerant of several functional groups including alkenes, halogens, nitro and heterocyclic groups. A reducing system composed of InBr3 and an economical hydrosiloxane, PMHS (polymethylhydrosiloxane) , enabled one-pot etherification by using a variety of aliphatic carboxylic acids and alcohols. Copyright
- Sakai, Norio,Usui, Yuta,Moriya, Toshimitsu,Ikeda, Reiko,Konakahara, Takeo
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p. 4603 - 4608
(2012/10/30)
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- New Pd(II) binuclear complexes as effective catalysts in oxidative-heck reaction using arylboronic acid derivatives
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A series of new binuclear Pd(II) complexes based on chelating diimines and bridging diphosphine or diimine ligands have been synthesized and characterized successfully. The formula of the new complexes are [Pd2(mbyp) 2(DPA)2](PF6)4 (1), [Pd 2(mbyp)2(DPE)2] (PF6)4 (2), [Pd2(mbyp)2(4,4-byp)2] (PF 6)4 (3), [Pd2(mbyp)2(t-pye) 2] (PF6)4 (4) [mbyp= 4,4-dimethyl-2,2- bipyridine, DPA= 1,2-bis(diphenylphosphino)acetylene, DPE= 1,2- bis(diphenylphosphino)ethylene, 4,4-byp= 4,4-bipyridine, and t-ype= trans 1,2-bis(4-pyridyl)ethylene)]. The catalytic activities of the new complexes have been investigated in the coupling of arylboronic acid derivatives to various olefins. Results obtained showed interesting catalytic activities and chemoselectivities for the new complexes in the coupling reactions to produce the conjugate addition and heck coupling products under free base or oxidant conditions.
- Suleiman, Rami,Shakil Hussain,Fettouhi, Mohammed,El Ali, Bassam
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scheme or table
p. 850 - 856
(2012/09/22)
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- Catalytic aerobic synthesis of aromatic ethers from non-aromatic precursors
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Only little waste: Aryl ether formation is accomplished by oxidative condensation of alcohols and 2-cyclohexenones. The reaction complements the existing methods used by synthetic chemists to obtain aryl ethers, and allows a straightforward access to a wide range of functionalized products. In addition, the catalytic reaction with O2 as the oxidant generates water as the only by-product and provides a greener approach to aryl ethers. Copyright
- Simon, Marc-Olivier,Girard, Simon A.,Li, Chao-Jun
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supporting information; experimental part
p. 7537 - 7540
(2012/09/10)
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- Electron transfer to benzenes by photoactivated neutral organic electron donor molecules
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Powerful reduction reactions: Simple organic electron donors, composed solely of the elements carbon, hydrogen, and nitrogen, reduce ground-state benzene rings to their radical anions by electron transfer upon photoactivation (DMF=dimethylformamide).
- Cahard, Elise,Schoenebeck, Franziska,Garnier, Jean,Cutulic, Sylvain P. Y.,Zhou, Shengze,Murphy, John A.
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p. 3673 - 3676
(2012/06/01)
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- Hybrid super electron donors - Preparation and reactivity
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Neutral organic electron donors, featuring pyridinylidene-imidazolylidene, pyridinylidene-benzimidazolylidene and imidazolylidene-benzimidazolylidene linkages are reported. The pyridinylidene-benzimidazolylidene and imidazolylidene-benzimidazolylidene hyb
- Garnier, Jean,Thomson, Douglas W.,Zhou, Shengze,Jolly, Phillip I.,Berlouis, Leonard E. A.,Murphy, John A.
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supporting information; experimental part
p. 994 - 1002
(2012/09/08)
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- One-pot reduction of aryl iodides using 4-DMAP methiodide salt
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An efficient one-pot procedure is described for the reduction of aryl iodides to aryl anions using a structurally simple bis-pyridinylidene electron donor, prepared in situ by treating 4-DMAP methiodide salt with base. The results show (i) that pyridinylidene carbenes can be easily used for intermolecular C-C bond formation, (ii) that bis-pyridinylidenes demonstrate superior robustness compared to electron-donor systems based on bis-imidazolylidenes, and (iii) that electron-donor strength is enhanced in the simplified DMAP-based donor. Deuterated analogues of this donor also provide mechanistic information on the source of protons when the aryl anions are quenched in situ. Georg Thieme Verlag Stuttgart.
- Garnier, Jean,Murphy, John A.,Zhou, Sheng-Ze,Turner, Andrew T.
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scheme or table
p. 2127 - 2131
(2009/05/07)
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- Super-electron donors: Bis-pyridinylidene formation by base treatment of pyridinium salts
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Deprotonation of bispyridinium salt 7b affords bispyridinylidene 10, a very powerful neutral organic two-electron donor [E1/2 (DMF) = -1.13 V vs Ag/AgCI/KCI (sat)], presumably via the pyridinylidene 8. Donor 10 reduces aryl iodides and bromides to aryl anions in excellent yield and also reductively cleaves selected phenylalkylsulfones very efficiently.
- Murphy, John A.,Gamier, Jean,Park, Stuart R.,Schoenebeck, Franziska,Zhou, Sheng-Ze,Turner, Andrew T.
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supporting information; experimental part
p. 1227 - 1230
(2009/04/06)
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- Copper(II)-catalyzed O-phenylation of alcohols with organobismuth(V) reagents: A convenient method for the synthesis of simple tert-alkyl phenyl ethers
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A convenient method for copper(II)-catalyzed O-phenylation of simple alcohols with organobismuth(V) compounds under mild conditions is described. Treatment of tetraphenylbismuth fluoride (Ph4BiF) with various simple alcohols in the presence of
- Mukaiyama, Teruaki,Sakurai, Naoto,Ikegai, Kazuhiro
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p. 1140 - 1141
(2007/10/03)
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- Copper(II)-catalyzed ether synthesis from aliphatic alcohols and potassium organotrifluoroborate salts
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(Matrix presented) A protocol for the copper(II)-catalyzed etherification of aliphatic alcohols under mild and essentially neutral conditions is described. Air- and moisture-stable potassium alkenyl- and aryltrifluoroborate salts undergo cross-coupling with a variety of aliphatic primary and secondary alcohols and phenols, and are tolerant of a range of functional groups. The optimized conditions utilize catalytic copper(II) acetate with 4-(dimethylamino)pyridine as ligand in the presence of 4 A molecular sieves under an atmosphere of oxygen.
- Quach, Tan D.,Batey, Robert A.
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p. 1381 - 1384
(2007/10/03)
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