- Catalytic Reductive Cross-Coupling between Aromatic Aldehydes and Arylnitriles
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A reductive cross-coupling reaction between aromatic aldehydes and arylnitriles using a copper catalyst and a silylboronate as a reductant is reported. This protocol represents an unprecedented approach to the chemoselective synthesis of α-hydroxy ketones by electrophile–electrophile cross-coupling.
- Mitsui, Atsuhisa,Nagao, Kazunori,Ohmiya, Hirohisa
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supporting information
p. 7094 - 7098
(2021/04/16)
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- Reductive coupling between aromatic aldehydes and ketones or imines by copper catalysis
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The copper-catalyzed reductive coupling of two different carbonyl compounds has been achieved. The reaction of aromatic aldehydes and arylketones with a silylboronate in the presence of a catalytic amount of a CuCl-N-heterocyclic carbene (NHC) complex and a stoichiometric amount of alkoxide base yielded cross-coupled 1,2-diol derivatives. A reaction pathway is proposed that involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(I) species from the aromatic aldehyde and its subsequent coupling with the arylketone. This process was amenable to asymmetric catalysis. This copper catalyst system also enabled the reductive coupling between aromatic aldehydes and imines.
- Takeda, Mitsutaka,Mitsui, Atsuhisa,Nagao, Kazunori,Ohmiya, Hirohisa
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supporting information
p. 3664 - 3669
(2019/02/14)
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- Novel biphenyl organocatalysts for iminium ion-catalyzed asymmetric epoxidation
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Two novel chiral biphenyl iminium salts derived from L-acetonamine, containing electron-withdrawing 3,30-substituents on the biphenyl unit, have been prepared and tested as asymmetric catalysts for epoxidation of prochiral alkenes. The results are compared with those achieved using the corresponding unsubstituted system.
- Farah, Mohamed M.,Page, Philip C. Bulman,Buckley, Benjamin R.,Blacker, A. John,Elsegood, Mark R.J.
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p. 758 - 769
(2013/07/27)
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- Hot water as a mild Bronsted acid catalyst in ring opening reactions of epoxides
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Ring opening of extremely hydrophobic epoxides with water, amines, sodium azide and thiophenol was realized in the mixture solvent of water and 1, 4-dioxane under reflux condition. Hot water was believed to act as a mild Bronsted acid catalyst in the epoxide-opening reactions.
- Xu, Zhaobing,Qu, Jin
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experimental part
p. 1718 - 1725
(2012/04/18)
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- Lanthanum tricyanide-catalyzed acyl silane-ketone benzoin additions and kinetic resolution of resultant α-silyloxyketones
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We report the full account of our efforts on the lanthanum tricyanide-catalyzed acyl silane-ketone benzoin reaction. The reaction exhibits a wide scope in both acyl silane (aryl, alkyl) and ketone (aryl-alkyl, alkyl-alkyl, aryl-aryl, alkenyl-alkyl, alkynyl-alkyl) coupling partners. The diastereoselectivity of the reaction has been examined in both cyclic and acyclic systems. Cyclohexanones give products arising from equatorial attack by the acyl silane. The diastereoselectivity of acyl silane addition to acyclic α-hydroxy ketones can be controlled by varying the protecting group to obtain either Felkin-Ahn or chelation control. The resultant α-silyloxyketone products can be resolved with selectivity factors from 10 to 15 by subjecting racemic ketone benzoin products to CBS reduction.
- Tarr, James C.,Johnson, Jeffrey S.
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supporting information; scheme or table
p. 3317 - 3325
(2010/08/05)
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- Novel and efficient Ni-mediated pinacol coupling of carbonyl compounds
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It was firstly found that the Rieke Ni generated in situ was able to promote the pinacol coupling of various carbonyls efficiently. Based on this information, another catalytically effective, cheaper and more convenient NiCl2(Cat.)/Mg/TMSCl system was designed and developed further successfully. The interesting single-electron transfer (SET) mechanisms for the coupling reactions were proposed. Additionally, the DL/meso diastereoselectivity and some additive effects were also explained in terms of the proposed mechanisms.
- Shi, Lei,Fan, Chun-An,Tu, Yong-Qiang,Wang, Min,Zhang, Fu-Min
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p. 2851 - 2855
(2007/10/03)
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- Synthesis of unsymmetrical diolate, oxametallacyclopentene, amido-alkoxide and thiolato-alkoxide complexes using dialkyl and diaryl titanium aminotroponiminate complexes: A route to unsymmetrical vicinal diols
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The reactivity of [TiR2(Me2ATI)2] complexes, where Me2ATI = N,N′-dimethylaminotroponiminate, or L, with CO or RNC in the presence of various organic electrophiles has been investigated. The compounds TiMe2L2 and TiPh2L2 react with CO and aldehydes or ketones to afford unsymmetrical diolate complexes that convert to the corresponding vicinal diols after hydrolysis. Phenyl acetylene also reacts to form the oxametallacyclopentene complex [Ti(OCMe2CH=CPh)(Me2ATI)2]. Treatment of TiMe2L2 with RNC yields the free imine and a source of low-valent titanium. Trapping this intermediate with 2 equiv of benzaldehyde or benzil affords the titanium diolate or enediolate complex, respectively. When 1 equiv each of benzophenone and either N-tosylbenzaldimine or acetone were added to the intermediate, [Ti(Ph2COCN(SO2tol)HPh)(Me2-ATI)2] and [Ti(Ph2COCOMe2)(Me2ATI)2], respectively, were obtained. The titanium thiolato-alkoxide complex [Ti(Ph2CSCOMe2)(Me2ATI)2] was prepared by use of thiobenzophenone and acetone. This chemistry allows for the preparation of unsymmetrical diols and oxametallacyclopentene complexes from Ti(IV) dialkyls, CO, and either carbonyl compounds or alkynes. Amido-alkoxide and thiolato-alkoxide complexes can be prepared by the reaction of Ti(IV) dialkyl complex, 2 equiv of benzophenone, and either an imine or thioketone.
- Steinhuebel, Dietrich P.,Lippard, Stephen J.
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p. 11762 - 11772
(2007/10/03)
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- Electrosyntheses from aromatic aldehydes in a flow cell. Part II. The cross-coupling of benzaldehydes to unsymmetrical diols
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It is demonstrated that the reduction of mixtures of two benzaldehydes in acidic water-methanol in a membrane flow cell with a lead cathode can lead to a mixture of diols including the unsymmetrical diol, e.g. 4-F-C6H4-CH(OH)-CH(OH)-C6H5. In the conditions employed, the ratio of the three diol products follows the statistical distribution expected for the coupling of two different radical intermediates produced in the same ratio as the concentrations of their precursors. The yield and current efficiency for the diols are excellent when the pH and potential are selected so that a 1e- reduction of both benzaldehydes occurs. The yield of unsymmetrical dimer based on one reactant can be increased substantially by using the other carbonyl compound as a sacrificial reagent. Acta Chemica Scandinavica 1998.
- Guena, Thierry,Pletcher, Derek
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- Diastereomerically Pure 3-(Silyloxy)oxetanes by a Selective Paterno-Buechi Reaction
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Diastereomerically pure 3-oxetanes 3 were prepared in moderate to good yields (45-72percent) by the Paterno-Buechi reaction of silyl enol ethers 2 with benzaldehyde.The phorocycloaddition exhibits a high degree of regio- and diastereoselectivity.The substituents R in the silyl enol ether have been varied , and it was found that steric bulk is mainly responsible for enhanced selectivity (diastereoselectivity from 70:30 up to 95:5).The regiochemical control is perfect (regioselectivity > 95:5) except for silyl enol ether 2a (R = Me) in the case of which a 90:10 ratio of regioisomers was observed.Irradiation of the reaction mixture at lower temperature (-25 deg C) led to a further improvement of diastereoselectivity.The relative configuration of the products obtained was elucidated both by 1H-NMR spectroscopy and by chemical degradation.As a mechanistic hypothesis to explain the high observed diastereoselectivity we propose that the steric environment in the intermediate diradical 11 determines the stereoselectivity according to two possible reaction pathways, i.e. bond formation and retrocleavage. - Key Words: Paterno-Buechi reaction / Oxetanes / Diastereoselectivity / Enol silyl ethers / Photocycloaddition
- Bach, Thorsten,Joedicke, Kai
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p. 2457 - 2466
(2007/10/02)
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- Anionic Zirconaoxiranes as Nucleophilic Aldehyde Equivalents. Application to Intermolecular Pinacol Cross Coupling
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Selective intermolecular pinacol cross coupling is achieved by reaction of anionic zirconaoxiranes with aromatic aldehydes and ketones, thereby providing an efficient route to unsymmetrical vicinal diols.
- Askham, Fredric R.,Carroll, Kevin M.
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p. 7328 - 7329
(2007/10/02)
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