- Efficient syntheses of enantiomerically pure 1,2-dicyclohexenyl- and 1,2-dicyclohexyl-1,2-ethanediol using B-2-cyclohexen-1-yl- diisopinocampheylborane
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The reaction of (+)-B-2-cyclohexen-1-yldiisopinocampheylborane with glyoxal at -78°C yields 98% stereoisomerically pure (1S,2S,1'R,1''R)-(+)- 1,2-bis(2-cyclohexenyl)-1,2-ethanediol in 81% yield. A simple crystallization of the above diol from hexane follo
- Chen, Guang-Ming,Ramachandran, P. Veeraraghavan
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- Influence of a dimetal ion binding ferrocene ligand on the samarium diiodide promoted pinacol coupling reaction
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Substantial yield increases have been noted in the use of a di-SmI2 binding ligand for the pinacol coupling of alkyl aldehydes compared to 1:1 complexes of SmI2 and tetraglyme. High diastereoselectivities of ca. 10:1 are also observed for α-substituted alkyl aldehydes in favour of the (±)-isomers.
- Christensen, Torben Birk,Riber, Ditte,Daasbjerg, Kim,Skrydstrup, Troels
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Read Online
- Facile pinacol coupling of aliphatic ketones by Brook rearrangement in the presence of samarium species
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Herein we report a practical pinacol coupling reaction, in which ketones (aldehydes) react smoothly with Sm and TMSBr to afford the diol products with Sm(II) or (III) siliyl species generated in situ. This reported method affords poor yields for aromatic ketone substrates and good yields for aliphatic ketones. Therefore, it distinguishes from most reductive coupling approaches that are more effective for aromatic carbonyl compounds and provides a facile and robust approach for the pinacol coupling of aliphatic ketones. Mechanistic studies also indicated the pinacolization probably proceeded via an anionic instead of radical coupling pathway involving the Brook rearrangement in the presence of samarium (II or III) silyl species.
- Wang, Xincan,Xie, Guanqun,Zhao, Yanfei,Zheng, Ke,Fang, Yanxiong,Wang, Xiaoxia
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supporting information
(2021/04/27)
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- Ambient-Pressure Asymmetric Preparation of S,S -DICHED, a C 2 -Symmetrical Director for Matteson Reactions
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A synthesis of S, S -DICHED (dicyclohexylethane-1,2-diol), a C 2 -symmetrical chiral director for Matteson homologations, is described. It relies on the insertion of lithiated S -2-cyclohexyloxirane into cyclohexylboronic acid pinacol ester and proceeds in three linear steps from readily available starting materials. No step requires chromatography or any specialized equipment.
- Bojaryn, Kevin,Hoffmann, Chris,Struth, Felix R.,Hirschh?user, Christoph
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supporting information
p. 1092 - 1094
(2018/01/27)
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- Pinacol couplings of a series of aldehydes and ketones with SmI2/Sm/Me3SiCl in DME
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The pinacol coupling is one of the most significant methods to synthesize vic-diols. The combination of samarium diiodide (SmI2) and samarium metal successfully induces the selective pinacol couplings of not only aromatic aldehydes and ketones but also aliphatic ones in the presence of trimethylchlorosilane (Me3SiCl) in 1,2-dimethoxyethane (DME). DME is the most suitable solvent for the reduction system using SmI2 and Me3SiCl. Me3SiCl, a widely available additive, prevents the decomposition of the formed vic-diols, i.e., meso-isomers, and controls their stereochemistry. In particular, the pinacol couplings of sterically hindered aliphatic aldehydes and ketones proceed with excellent diastereoselectivities to afford dl-isomers in good yields.
- Yoshimura, Aya,Saeki, Tomokazu,Nomoto, Akihiro,Ogawa, Akiya
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p. 5347 - 5355
(2015/07/15)
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- Mechanistic study of half-titanocene-based reductive pinacol coupling reaction
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The reductive pinacol coupling reaction of aldehydes or ketones creating a new C-C bond has been a major tool to produce 1,2-diol compounds. The reaction mechanism is known to be composed of sequential three steps (activation, coupling, and dissociation). In this work, we studied the dissociation step of half-titanocene-based catalytic systems. Cp and Cp* derivatives of the pinacolato-bridged dinuclear complex were synthesized and evaluated as possible models for intermediates from the coupling step. We monitored 1H-NMR spectra of the reaction between the metalla-pinacol intermediates and D2O. New reaction routes of the dissociation step including oxo- and pinacolato-dibridged dinuclear complexes and oxo-bridged multinuclear complexes have been suggested. Copyright
- Kim, Youngjo,Do, Youngkyu,Park, Sungjin
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experimental part
p. 3973 - 3978
(2012/03/26)
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- A new Yb3+-catalyzed pinacol and imine-coupling reaction
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Ytterbium triflate, Yb(OTf)3, catalyzes the intermolecular reductive homocouplings of imines, aldehydes, and ketones at loadings of 5 mol % in the presence of Mg and Me3SiCl to give isolated yields of up to 95%. Diastereoselectivity of up to 4/96 (dl/meso) is achieved for aromatic aldehydes, up to 100% dl for aliphatic aldehydes, and 100% dl for an intramolecular imine coupling.
- Aspinall, Helen C.,Greeves, Nicholas,Hin, Shane Lo Fan
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experimental part
p. 1558 - 1561
(2010/06/13)
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- Reductive self-coupling reaction of imines and aldehydes induced by strontium metal
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Aromatic aldimines reacted with Sr in the presence of a catalytic amount of iodine to give self-coupling products in good yields, whereas aromatic and aliphatic aldehydes underwent a similar reaction effected by the combined use of Sr and Al(OEt)3. Copyright
- Miyoshi, Norikazu,Kohno, Tadashi,Wada, Makoto,Matsunaga, Sei,Mizota, Isao,Shimizu, Makoto
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experimental part
p. 984 - 985
(2012/10/18)
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- Samarium diiodide-catalyzed diastereoselective pinacol couplings
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(Chemical Equation Presented) A complex of samarium diiodide (Sml 2) with tetraglyme catalyzes the intermolecular pinacol coupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me2SiCl2 and Mg. Diastereoselectivity of up to 95/5 (±/meso) has been achieved for aliphatic aldehydes and up to 19/81 (±/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling reactions using the Sml 2/tetraglyme/Mg/Me2SiCl2 catalytic system.
- Aspinall, Helen C.,Greeves, Nicholas,Valla, Carine
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p. 1919 - 1922
(2007/10/03)
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- Catalytic, highly enantio- and diastereoselective pinacol coupling reaction with a new tethered bis(8-quinolinolato) ligand
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A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is developed. Its chromium complex, TBOxCrCl (3 mol %), effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diast
- Takenaka, Norito,Xia, Guoyao,Yamamoto, Hisashi
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p. 13198 - 13199
(2007/10/03)
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- Efficient diastereoselective pinacol coupling reaction of aliphatic and aromatic aldehydes by using newly utilized low valent titanium bromide and iodide species
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Reductive coupling reaction of aromatic and aliphatic aldehydes proceeded under mild conditions to give the corresponding pinacols in moderate to high yields and DL-diastereoselectivities by using combinations of either low valent titanium(II) bromide and copper or titanium(IV) iodide and copper in a mixed solvent of dichloromethane and pivalonitrile. In the case of using titanium(IV) iodide and copper, pinacols were obtained in good to high yields with moderate to high diastereoselectivities irrespective of the number of substitutuents at α-position of aliphatic aldehydes.
- Mukaiyama, Teruaki,Yoshimura, Naritoshi,Igarashi, Koji,Kagayama, Akifumi
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p. 2499 - 2506
(2007/10/03)
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- Efficient diastereoselective pinacol reaction of aliphatic and aromatic aldehydes by combined use of newly utilized titanium(II) bromide and copper
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Newly utilized low-valent titanium reductant, titanium(II) bromide, was conveniently prepared by treating titanium(IV) bromide with hexamethyldisilane. The pinacol reaction of aromatic and aliphatic aldehydes including primary aldehydes proceeded smoothly in dichloromethane-pivalonitrile at temperatures ranging from -23 to 0 °C by the combined use of soluble titanium(II) bromide and copper to give 1,2-diols in good to high yields with good to high dl-selectivities.
- Mukaiyama, Teruaki,Kagayama, Akifumi,Igarashi, Koji
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p. 336 - 337
(2007/10/03)
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- The effect of Lewis acids on the pinacol homocoupling reaction of aldehydes promoted by samarium diiodide
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The effect of various Lewis acids on the samarium diiodide promoted pinacol homocoupling of aldehydes was investigated. The reaction of benzaldehyde proceeded with fair to good 1,2-anti-stereoselectivity, while in the case of other aromatic and aliphatic aldehydes syn-stereoselectivity was generally observed. Chiral α-alkylaldehydes allowed for an almost complete stereocontrol favoring syn-1,2-diols.
- Annunziata, Rita,Benaglia, Maurizio,Cinquini, Mauro,Raimondi, Laura
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p. 3369 - 3374
(2007/10/03)
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- Ligand effects on the diastereoselectivities of samarium diiodide promoted pinacol coupling
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The samarium diiodide pinacol coupling of benzaldehyde and cyclohexanecarboxaldehyde in the presence of a variety of polyethylene glycols, including derivatives containing carbohydrates has been studied. Whereas such complexing agents allow for the format
- Pedersen, Henriette Lodberg,Christensen, Torben Birk,Enemaerke, Rasmus Juel,Daasbjerg, Kim,Skrydstrup, Troels
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p. 565 - 572
(2007/10/03)
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- Stereoselective Synthesis of Alcohols, XXXI. - Stereoselective C-C Bond Formation Using Chiral Z-Pentenylboronates
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Using 1,2-dicyclohexyl-1,2-ethanediol as chiral auxiliary, the enantiomerically pure Z-pentenylboronate 9c was obtained.Its addition to benzaldehyde proceeded with complete transfer of chirality to give the syn-E-homoallyl alcohol 11.The ability of the re
- Hoffmann, Reinhard W.,Ditrich, Klaus,Koester, Gerhard,Stuermer, Rainer
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p. 1783 - 1790
(2007/10/02)
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