- Alkali salt of L-proline as an efficient and practical catalyst for the cyanosilylation of a wide variety of carbonyl compounds under solvent-free conditions
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The alkali salt of L-proline was demonstrated to be an efficient and practical catalyst for the cyanosilylation of a wide variety of simple and functionalized carbonyl compounds under solvent-free conditions. The reactions proceeded smoothly at room temperature to afford the corresponding cyanohydrins in good to excellent yields. Copyright Taylor & Francis Group, LLC.
- Shen, Zhi-Liang,Ji, Shun-Jun
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Read Online
- Ionic liquid [omim][PF6] as an efficient and recyclable reaction media for the cyanosilylation of aldehydes without Lewis acid or any special activation
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Ionic liquid [omim][PF6] has been demonstrated as an efficient and environmentally friendly reaction media as well as a promoter for the cyanosilylation of aldehydes under mild conditions. In addition, the recovered ionic liquid could be reused for subsequent runs with only a gradual decrease in activity.
- Shen, Zhi-Liang,Ji, Shun-Jun,Loh, Teck-Peng
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Read Online
- CO2-Enabled Cyanohydrin Synthesis and Facile Iterative Homologation Reactions**
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Thermodynamic and kinetic control of a chemical process is the key to access desired products and states. Changes are made when a desired product is not accessible; one may manipulate the reaction with additional reagents, catalysts and/or protecting groups. Here we report the use of carbon dioxide to accelerate cyanohydrin synthesis under neutral conditions with an insoluble cyanide source (KCN) without generating toxic HCN. Under inert atmosphere, the reaction is essentially not operative due to the unfavored equilibrium. The utility of CO2-mediated selective cyanohydrin synthesis was further showcased by broadening Kiliani–Fischer synthesis under neutral conditions. This protocol offers an easy access to a variety of polyols, cyanohydrins, linear alkylnitriles, by simply starting from alkyl- and arylaldehydes, KCN and an atmospheric pressure of CO2.
- Juhl, Martin,Petersen, Allan R.,Lee, Ji-Woong
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supporting information
p. 228 - 232
(2020/11/30)
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- CO2-Mediated Non-Destructive Cyanide Wastewater Treatment
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The facile removal of cyanide anions from cyanide-containing water was achieved using CO2 in conjunction with aldehydes which can be recycled from the process. The conversion of the cyanide ion into an insoluble cyanohydrin in water allowed the removal of cyanide and could be used as a method for treating cyanide contaminated wastewater and for recovering cyanide or cyanohydrins for further applications.
- Juhl, Martin,Lee, Ji-Woong,Petersen, Allan R.,Petrovic, Aleksa
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supporting information
p. 5003 - 5007
(2021/09/30)
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- Nickel-Catalyzed, Reductive C(sp3)?Si Cross-Coupling of α-Cyano Alkyl Electrophiles and Chlorosilanes
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A nickel/zinc-catalyzed cross-electrophile coupling of alkyl electrophiles activated by an α-cyano group and chlorosilanes is reported. Elemental zinc is the stoichiometric reductant in this reductive coupling process. By this, a C(sp3)?Si bond can be formed starting from two electrophilic reactants whereas previous methods rely on the combination of carbon nucleophiles and silicon electrophiles or vice versa.
- Oestreich, Martin,Zhang, Liangliang
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supporting information
p. 18587 - 18590
(2021/07/25)
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- Access to β-Ketonitriles through Nickel-Catalyzed Carbonylative Coupling of α-Bromonitriles with Alkylzinc Reagents
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Herein, we report a nickel-catalyzed carbonylative coupling of α-bromonitriles and alkylzinc reagents with near stoichiometric carbon monoxide to give β-ketonitriles in good yields. The reaction is catalyzed by a readily available and stable nickel(II) pincer complex. The developed protocol tolerates substrates bearing a variety of functional groups, which would be problematic or incompatible with previous synthetic methods. Additionally, we demonstrate the suitability of the method for carbon isotope labeling by the synthesis of 13C-labeled β-ketonitriles and their transformation into isotopically labeled heterocycles.
- Donslund, Aske S.,Neumann, Karoline T.,Corneliussen, Nicklas P.,Grove, Ebbe K.,Herbstritt, Domenique,Daasbjerg, Kim,Skrydstrup, Troels
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supporting information
p. 9856 - 9860
(2019/07/09)
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- Metallation–substitution of an α-oxygenated chiral nitrile
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Deprotonation of a chiral alpha-oxygenated nitrile with the base 2,2,6,6-tetramethylpiperidylmagnesium chloride, TMPMgCl, gives rise to a chiral magnesiated nitrile, and this anion has sufficient configurational stability at low temperature to allow the formation of highly enantiomerically enriched substituted nitrile products after electrophilic quench.
- Alshawish, Madeha R.,Barker, Graeme,Measom, Nicholas D.,Coldham, Iain
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p. 601 - 608
(2017/05/24)
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- Hydroxynitrile Lyase Isozymes from Prunus communis: Identification, Characterization and Synthetic Applications
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Biocatalysts originating from Badamu (Prunus communis) have been applied to catalyze the asymmetric synthesis of (R)-4-methylsulfanylmandelonitrile, a key building block of thiamphenicol and florfenicol. Here, four hydroxynitrile lyase (HNL) isozymes from Badamu were cloned and heterologously expressed in Pichia pastoris. The biochemical properties and catalytic performances of these isozymes were comprehensively explored to evaluate their efficiency and selectivity in asymmetric synthesis. Among then, PcHNL5 was identified with outstanding activity and enantioselectivity in asymmetric hydrocyanation. Under the optimized mild biphasic reaction conditions, seventeen prochiral aromatic aldehydes were converted to valuable chiral cyanohydrins with good yields (up to 94%) and excellent optical purities (up to >99.9% ee), which provide a facile access to numerous chiral amino alcohols, hypoglycemic agents, angiotension converting enzyme (ACE) inhibitors and β-blockers. This work therefore underlines the importance of discovering the most potent biocatalyst among a group of isozymes for converting unnatural substrates into value-added products. (Figure presented.).
- Zheng, Yu-Cong,Xu, Jian-He,Wang, Hui,Lin, Guo-Qiang,Hong, Ran,Yu, Hui-Lei
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p. 1185 - 1193
(2017/04/13)
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- Copper-Catalyzed Substitution of α-Triflyloxy Nitriles and Esters with Silicon Nucleophiles under Inversion of the Configuration
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A copper-catalyzed nucleophilic displacement of α-triflyloxy nitriles and esters with silicon nucleophiles allows for the stereospecific generation of highly enantioenriched α-silylated carboxyl compounds. The enantioselective synthesis of α-silylated nitriles is unprecedented. The catalytic system exhibits good functional group tolerance. The stereochemical course of the substitution is shown to proceed with inversion of the configuration. The new reaction is an addition to the still limited number of methods for catalytic C(sp3)-Si cross-coupling.
- Scharfbier, Jonas,Hazrati, Hamideh,Irran, Elisabeth,Oestreich, Martin
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supporting information
p. 6562 - 6565
(2017/12/26)
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- Nickel-Catalyzed Asymmetric Reductive Cross-Coupling between Heteroaryl Iodides and α-Chloronitriles
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A Ni-catalyzed asymmetric reductive cross-coupling of heteroaryl iodides and α-chloronitriles has been developed. This method furnishes enantioenriched α,α-disubstituted nitriles from simple organohalide building blocks. The reaction tolerates a variety of heterocyclic coupling partners, including pyridines, pyrimidines, quinolines, thiophenes, and piperidines. The reaction proceeds under mild conditions at room temperature and precludes the need to pregenerate organometallic nucleophiles.
- Kadunce, Nathaniel T.,Reisman, Sarah E.
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p. 10480 - 10483
(2015/09/28)
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- Chemoenzymatic flow cascade for the synthesis of protected mandelonitrile derivatives
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A chemoenzymatic two-step cascade process, with both steps having incompatible reaction conditions, was successfully performed in continuous flow. The chemoenzymatic aqueous formation of cyanohydrins was integrated with a subsequent organic phase protection step in a single flow process utilising a membrane-based phase separation module. The wider applicability of our setup was demonstrated with the synthesis of nine protected cyanohydrin derivatives, all obtained in good yields and high to excellent enantioselectivity.
- Delville, Marille M. E.,Koch, Kaspar,Van Hest, Jan C. M.,Rutjes, Floris P. J. T.
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supporting information
p. 1634 - 1638
(2015/03/05)
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- A magnetic nanoparticle catalyzed eco-friendly synthesis of cyanohydrins in a deep eutectic solvent
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Magnetic Fe3O4 nanoparticles in deep eutectic solvents (DESs) have been regard as excellent catalysts for highly efficient cyanosilylation of various aldehydes and epoxides using trimethylsilyl cyanide TMSCN in high yields with excellent selectivity. Fe3O4 nanoparticles were synthesized and applied as a catalyst for the preparation of a wide variety of cyanohydrins (α-hydroxy nitriles and β-hydroxy nitriles) in readily available urea-choline chloride deep eutectic solvent DES as the most promising environmentally benign and cost-effective green solvent. Magnetic DES operates at very mild reaction conditions and can be easily recycled without significant loss of its catalytic activity.
- Azizi, Najmedin,Rahimi, Zahra,Alipour, Masoumeh
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p. 61191 - 61198
(2015/07/28)
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- Improving the properties of bacterial r-selective hydroxynitrile lyases for industrial applications
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Hydroxynitrile lyases (HNLs) catalyse the reversible cleavage of cyanohydrins to carbonyl compounds and HCN. The recent discovery of bacterial HNLs with a cupin fold gave rise to a new promising class of these enzymes. They are interesting candidates for the synthesis of cyanohydrins on an industrial scale owing to their high expression levels in Escherichia coli. The activity and enantioselectivity of the manganese-dependent HNL from Granulicella tundricola (GtHNL) were significantly improved by site-saturation mutagenesis of active site amino acids. The combination of beneficial mutations resulted in a variant with 490-fold higher specific activity in comparison to the wild-type enzyme. More importantly, GtHNL-A40H/V42T/Q110H is a highly competitive alternative for the synthesis of chiral cyanohydrins, such as 2-chlorobenzaldehyde cyanohydrin, (R)-2-hydroxy-4-phenylbutyronitrile, and (R)-2-hydroxy-4-phenyl-3-butene nitrile, which serve as intermediates for the synthesis of pharmaceuticals.
- Wiedner, Romana,Kothbauer, Bettina,Pavkov-Keller, Tea,Gruber-Khadjawi, Mandana,Gruber, Karl,Schwab, Helmut,Steiner, Kerstin
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p. 325 - 332
(2015/03/05)
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- (R)-selective hydroxynitrile lyase variants with a cupin fold having improved substrate scope and the use thereof
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The present invention relates to an improved recombinant cupin-hydroxynitrile lyase (HNL), which is capable to catalyze the asymmetric cyanohydrin reaction, wherein the recombinant cupin-HNL comprises at least one amino acid substitution, preferably at le
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Paragraph 0082; 0083
(2015/12/31)
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- Kinetic resolution of mandelate esters via stereoselective acylation catalyzed by lipase PS-30
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By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic mandelate esters has been achieved via stereoselective acylation. The value of kinetic enantiomeric ratio (E) reached up to 197.5. Substituent effect is briefly discussed.
- Chen, Peiran,Yang, Wenhong
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supporting information
p. 2290 - 2294
(2014/04/17)
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- Silylcyanation of aldehydes, ketones, and imines catalyzed by a 6,6'-bis-sulfonamide derivative of 7,7'-dihydroxy-8,8'-biquinolyl (azaBINOL)
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6,6'-Bis(methylaminosulfonyl)-7,7'-dihydroxy-8,8'-biquinolyl (3) catalyzes (5-10 mol-%) the addition of trimethylsilyl cyanide to aldehydes (aryl, alkyl, and α,β-unsaturated; 42-92 % yields), ketones (aryl alkyl, dialkyl; 22-82 % yields), and N-benzylaldimines (14-78 % yields) in toluene (0 °C or room temp.) to give the expected cyanohydrin and Strecker adducts following desilylation. Among a series of closely related compounds lacking any one of their defining structural features, bis-sulfonamide 3 and its N,N'-dimethyl derivative are exceptional in catalyzing the silylcyanation of benzaldehyde in the absence of all other additives. Hammett analysis of the competitive silylcyanation of para-substituted benzaldehydes catalyzed by 3 showed a linear free-energy relationship (R2 = 0.928) with a modest positive reaction constant (ρ = +1.52). X-ray diffraction analysis of (±)-3 indicated a cisoid biaryl conformation and the existence of an intramolecular hydrogen bond between C7'-OH and C7-O. Resolution of (±)-3 was achieved by HPLC separation of its tetravalerate derivative on a chiral stationary phase. The absolute configurations of the optical isomers of 3 were assigned by correlation of the ECD spectra with those of related biquinolyls of known configuration. The silylcyanation of aldehydes catalyzed by (-)-(aR)-3 leads to cyanohydrins with a preference for the (S)-configured product with an ee of 10 %. The organocatalytic action of 3 is ascribed to hydrogen bonding and Bronsted acid catalysis effects that are dependent on its acidifying sulfonamide groups, general base capability, and interannular proximity effects made possible by the biaryl structure. Copyright
- Sephton, Selena Milicevic,Wang, Chao,Zakharov, Lev N.,Blakemore, Paul R.
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experimental part
p. 3249 - 3260
(2012/08/08)
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- Redox-neutral α-cyanation of amines
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α-Aminonitriles inaccessible by traditional Strecker chemistry are obtained in redox-neutral fashion by direct amine α-cyanation/N-alkylation or alternatively, α-aminonitrile isomerization. These unprecedented transformations are catalyzed by simple carboxylic acids.
- Ma, Longle,Chen, Weijie,Seidel, Daniel
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supporting information
p. 15305 - 15308
(2012/10/29)
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- Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
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Enzymatic kinetic resolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kinetic resolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was discussed. Under the optimized reaction conditions, good enantioselectivity could be achieved for most of the investigated compounds. Specifically, substrates 1a, 1c, 1d, 1f, 1u could be resolved with the kinetic enantiomer ratio (E) higher than 200.
- Xu, Qing,Xie, Yongli,Geng, Xiaohong,Chen, Peiran
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experimental part
p. 624 - 630
(2010/09/07)
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- Asymmetric synthesis of a new salen type-titanium complex as the catalyst for asymmetric trimethylsilylcyanation of aldehydes
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This work describes the asymmetric synthesis of a new salen-type ligand via a Diels-Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
- Lin, Zheng-Chang,Chen, Chinpiao
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experimental part
p. 726 - 737
(2011/04/23)
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- Room-temperature synthesis of enantioenriched non-protected cyanohydrins using vanadium(salalen) catalyst
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Room-temperature synthesis of enantioenriched non-protected cyanohydrins using acetone cyanohydrin as the cyanide source was achieved by V(salalen) catalyst. Aliphatic aldehydes underwent the cyanation with 89-95% ee in the presence of only 0.2-0.4 mol% catalyst. Aromatic cyanohydrins were also obtained in high enantiomeric excesses under modified conditions.
- Sakai, Yoshifumi,Mitote, Junko,Matsumoto, Kazuhiro,Katsuki, Tsutomu
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supporting information; experimental part
p. 5787 - 5789
(2010/09/05)
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- Dibutyltin dimethoxide-catalyzed cyano transfer to aldehydes and imines
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A novel reaction involving cyano transfer from benzophenone cyanohydrin to aldehydes and imines was realized by using dibutyltin dimethoxide as a catalyst. Various cyanohydrins and α-amino nitriles were obtained in moderate to high yields by this reaction. Ketimines also showed remarkable reactivity as cyano acceptors under conventional reaction conditions. This catalytic reaction was further applied to a three-component condensation reaction of aldehydes, aniline, and benzophenone cyanohydrin in the presence of Drierite. Copyright
- Yanagisawa, Akira,Matsumoto, Takuya,Kushihara, Naoyuki,Yoshida, Kazuhiro
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experimental part
p. 2918 - 2922
(2011/01/05)
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- Chiral solvating agents for cyanohydrins and carboxylic acids
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We have shown that a structure as simple as an ion pair of (R)- or (S)-mandelate and dimethylamminopyridinium ions possesses structural features that are sufficient for NMR enantiodiscrimination of cyanohydrins. Moreover, 1H NMR data of cyanohydrins of known configuration obtained in the presence of the mandelate-dimethylaminopyridinium ion pair point to the existence of a correlation between chemical shifts and absolute configuration of cyanohydrins. Mandelate-DMAPH+ ion pair and mandelonitrile form a 1:1 complex with an association constant of 338 M-1 (ΔG 0, -3.4 kcal/mol) for the (R)-mandelonitrile/(R)-mandelate-DMAPH + and 139 M-1 (ΔG0, -2.9 kcal/mol) for the (R)-mandelonitrile/(S)-mandelate-DMAPH+ complex. To understand the origin of enantiodiscrimination, the geometry optimization and energy minimization of the models of ternary complexes of (S)-mandelonitrile/(R)- mandelate/DMAPH+ and (S)-mandelonitrile/(S)-mandelate/DMAPH + complexes was performed using DFT methodology (B3LYP) with the 6-31+G(d) basis set in Gaussian 3.0. Further, analysis of optimized molecular model obtained from theoretical studies suggested that (i) DMAP may be replaced with other amines, (ii) the hydroxyl group of mandelic acid is not necessary for stabilization of ternary complex and may be replaced with other groups such as methyl, (iii) the ion pair should form a stable ternary complex with any hydrogen-bond donor, provided its OH bond is sufficiently polarized, and (iv) α-H of racemic mandelic acid should also get resolved with optically pure mandelonitrile. These inferences were experimentally verified, which not only validated the proposed model but also led to development of a new chiral solvating agent for determination of ee of carboxylic acids and absolute configuration of aryl but not alkyl carboxylic acids.
- Moon, Lomary S.,Pal, Mohan,Kasetti, Yoganjaneyulu,Bharatam, Prasad V.,Jolly, Ravinder S.
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body text
p. 5487 - 5498
(2010/11/05)
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- IMIDAZOL[1,2-alpha]QUINOXALINES AND DERIVATIVES FOR THE TREATMENT OF CANCERS
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Imidazo[1,2-a]quinoxaline compounds for the treatment of cancers as well as pharmaceutical compositions that include these compounds and their uses in therapy. The compound of general formula (I):
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Page/Page column 9
(2010/10/19)
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- Chirality transfer from epoxide to carbanion: Base-induced alkylation of O-carbamoyl cyanohydrins of β-silyl-α,β-epoxy aldehyde
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Enantioselective C-C bond formation at an α-position of a nitrile group with an external electrophile can be realized, although in modest ee, with the aid of both the concerted process of an epoxysilane rearrangement and a carbamoyl group. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Sasaki, Michiko,Kawanishi, Eiji,Shirakawa, Yuri,Kawahata, Masatoshi,Masu, Hyuma,Yamaguchi, Kentaro,Takeda, Kei
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supporting information; experimental part
p. 3061 - 3064
(2009/05/26)
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- A new strategy for designing non-C2-symmetric monometallic bifunctional catalysts and their application in enantioselective cyanation of aldehydes
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A monometallic bifunctional catalyst, in which only one imidazolyl moiety is directly attached at the 3-position of a binaphthol moiety, has been developed. The ligand (R)-1, which lacks C2-symmetry and flexible linkers, in combination with Ti(OiPr)4, has been demonstrated to promote the enantioselective cyanation of aldehydes with trimethylsilylcyanide (TMSCN), giving excellent enantioselectivities of up to 98 % ee and high yields of up to 99%. The use of this bifunctional catalytic system obviates the need for additives and is extremely simple as the reagents are added in one portion at the beginning of the reaction. The protocol has been found to tolerate a relatively wide range of aldehydes when 10 mol% of the (R)-1/Ti(OiPr) 4 complex is deployed in CH2Cl2 at -40°C, the conditions which proved most practical and effective. The asymmetric cyanations also proceeded with lower catalyst loadings (5 mol%, or even 2 mol%), still giving satisfactory enantiomeric excesses and yields. Interestingly, the use of freshly distilled TMSCN dried over CaH2 gave a low enantioselectivity and only a moderate yield of the adduct as compared with direct use of the commercial reagent. The results of 13C NMR spectroscopic studies implicate HCN as the actual reactive nucleophile.
- Yang, Fei,Wei, Siping,Chen, Chien-An,Xi, Peihua,Yang, Li,Lan, Jingbo,Gau, Han-Mou,You, Jingsong
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supporting information; experimental part
p. 2223 - 2231
(2009/04/06)
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- Kinetic resolution of cyanohydrins via enantioselective acylation catalyzed by lipase PS-30
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By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic cyanohydrins has been achieved via enantioselective acylation. The values of kinetic enantiomeric ratio (E) reached up to 314. Substituent effect is also briefly discussed.
- Xu, Qing,Geng, Xiaohong,Chen, Peiran
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scheme or table
p. 6440 - 6441
(2009/04/06)
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- A novel chiral (salen)AlIII complex catalyzed asymmetric cyanosilylation of aldehydes
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A novel chiral (salen)AlIII complex was synthesized through the reaction of Et2AlCl and salen (R,R)-1 derived from (R,R)-11,12-diamino-9,10-dihydro-9,10-ethanoanthracene. This complex is an efficient catalyst for the asymmetric trimethylsilylcyanation of aldehydes in the presence of tributylphosphane oxide as an additive. The use of 1 mol-% of the complex led to the corresponding cyanohydrins in high yields (85-94%) with good-to-excellent enantioselectivities (42-92%ee). Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Zeng, Zebing,Zhao, Guofeng,Zhou, Zhenghong,Tang, Chuchi
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experimental part
p. 1615 - 1618
(2009/04/11)
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- Vanadium-catalyzed asymmetric transcyanation of aliphatic aldehydes with acetone cyanohydrin
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The vanadium(V)(salalen) complex prepared in situ from the corresponding vanadium(IV) complex 4 under aerobic conditions was found to be an excellent catalyst for asymmetric transcyanation of aliphatic aldehydes with acetone cyanohydrin as the cyanide sou
- Takaki, Junko,Egami, Hiromichi,Matsumoto, Kazuhiro,Saito, Bunnai,Katsuki, Tsutomu
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p. 502 - 503
(2008/09/21)
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- One-pot synthesis of α-siloxy esters using a silylated masked acyl cyanide
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Synthesis of α-siloxy esters via a one-pot reaction from various aldehydes and alcohols using a masked acyl cyanide (MAC) reagent bearing tert-butyldimethylsilyl group is described. Georg Thieme Verlag Stuttgart.
- Nemoto, Hisao,Ma, Rujian,Kawamura, Tomoyuki,Yatsuzuka, Kenji,Kamiya, Masaki,Shibuya, Masayuki
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experimental part
p. 3819 - 3827
(2009/06/18)
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- Cyanosilylation of aldehydes and ketones catalyzed by nanocrystalline magnesium oxide
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Cyanosilylation of various aldehydes and ketones with TMSCN proceeded smoothly under mild conditions to give the corresponding cyanohydrin trimethylsilyl ethers in the presence of nanocrystalline magnesium oxide. The cyanohydrin trimethylsilyl ethers of aldehydes produced cyanohydrins in good to high yields on treatment with 2 N HCl. 29Si NMR spectral evidence proved that the reaction proceeds through the hypervalent silicate species by coordination to O2-/O- (Lewis basic site) of nanocrystalline magnesium oxide. Copyright Taylor & Francis Group, LLC.
- Lakshmi Kantam,Mahendar, Koosam,Sreedhar, Bojja,Vijay Kumar,Choudary
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experimental part
p. 3919 - 3936
(2009/04/11)
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- Synthesis of the bifunctional BINOL ligands and their applications in the asymmetric additions to carbonyl compounds
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Efficient one-step syntheses of the bifunctional BINOL and H8BINOL ligands (S)-6 and (S)-8 have been developed from the reaction of BINOL and H8BINOL with morpholinomethanol, respectively. The X-ray analyses of these compounds have revealed their structural similarity and difference. The bifunctional H8BINOL (S)-8 is found to be highly enantioselective for the reaction of diphenylzinc with many aliphatic and aromatic aldehydes and especially is the most enantioselective catalyst for linear aliphatic aldehydes. Unlike other catalysts developed for the diphenylzinc addition which often require the addition of a significant amount of diethylzinc with cooling (or heating) the reaction mixture in order to achieve high enantioselectivity, using (S)-8 needs no additive and gives excellent results at room temperature. (S)-8 in combination with diethylzinc and Ti(OiPr)4 can catalyze the highly enantioselective phenylacetylene addition to aromatic aldehydes. It can also promote the phenylacetylene addition to acetophenone at room temperature though the enantioselectivity is not very high yet. Without using Ti(OiPr)4 and a Lewis base additive, (S)-8 in combination with diethylzinc can catalyze the reaction of methyl propiolate with an aldehyde to form the highly functional γ-hydroxy-α,β-acetylenic esters except that the enantioselectivity is low at this stage. The bifunctional BINOL ligand (S)-6 in combination with Me2AlCl is found to be a highly enantioselective catalyst for the addition of TMSCN to both aromatic and aliphatic aldehydes.
- Qin, Ying-Chuan,Liu, Lan,Sabat, Michal,Pu, Lin
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p. 9335 - 9348
(2007/10/03)
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- Highly efficient trialkylsilylcyanation of aldehydes, ketones and imines catalyzed by a nucleophilic N-heterocyclic carbene
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The synthetic utility of N-heterocyclic carbenes was demonstrated by the trialkylsilylcyanation of aldehydes, ketones and imines. In the presence of a catalytic amount of 3a, the reactions with Me3SiCN proceeded smoothly to give the corresponding cyanohydrin trimethylsilyl ethers or amino nitrile derivatives in good to excellent yields.
- Kano, Taichi,Sasaki, Kouji,Konishi, Teppei,Mii, Haruka,Maruoka, Keiji
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p. 4615 - 4618
(2007/10/03)
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- An N-heterocyclic carbene as a nucleophilic catalyst for cyanosilylation of aldehydes
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The first method for cyanosilylation of aldehydes with trimethylsilyl cyanide in the presence of the N-heterocyclic carbene prepared from 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride and potassium tert-butoxide, as a nucleophilic catalyst, is described. Georg Thieme Verlag Stuttgart.
- Fukuda, Yoshimasa,Maeda, Yuka,Ishii, Satoru,Kondo, Kazuhiro,Aoyama, Toyohiko
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p. 589 - 590
(2007/10/03)
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- Asymmetric cyanohydrin synthesis catalyzed by Al(salen)/triphenylphosphane oxide
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Various aldehydes undergo asymmetric trimethylsilylcyanation with (CH 3)3SiCN (TMSCN) in the presence of a chiral Al(salen) complex and Ph3PO as the catalyst. This is a double activation where Al(salen) plays the role of Lewis acd and POPh3 acts as a Lewis base. Various kind of aldehydes were subjected to the enantioselective addition of (CH3)3SiCN at temperatures between -40 °C and -50 °C. Hydrolysis of the adducts gave cyanohydrins with over 90 % yield and 80 % ee in most cases. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Kim, Sung Soo,Song, Dae Ho
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p. 1777 - 1780
(2007/10/03)
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- Catalyst-free DMSO-promoted synthesis of cyanohydrin carbonates from aldehydes
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A variety of cyanohydrin carbonates were readily prepared from aldehydes with cyanoformate in DMSO using no catalyst in a convenient one-pot procedure.
- Iwanami, Katsuyuki,Hinakubo, Yumi,Oriyama, Takeshi
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p. 5881 - 5883
(2007/10/03)
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- P(RNCH2CH2)N: Efficient catalysts for the cyanosilylation of aldehydes and ketones
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The 1,2-addition of trialkylsilylcyanides to aldehydes and ketones produces the corresponding protected cyanohydrins in good to excellent yields when carried out at 0°C to room temperature in the presence of catalytic amounts of the nonionic strong base P(RNCH2CH2)N (R = Me, i-Pr) in THF. These catalysts are easily removed from the product by hydrolysis or column filtration through silica gel.
- Fetterly, Brandon M.,Verkade, John G.
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p. 8061 - 8066
(2007/10/03)
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- Development of β-hydroxyamide/titanium complexes for catalytic enantioselective silylcyanation of aldehydes
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A highly enantioselective addition of trimethylsilylcyanide to aldehydes catalyzed by chiral titanium complexes is described. The chiral titanium complexes were prepared in situ from Ti(OiPr)4 and β-hydroxyamide ligands, that could easily be synthesized from ketopinic acid and C2 symmetrical chiral diamines in a small number of steps. Graphical Abstract.
- Uang, Biing-Jiun,Fu, I-Pin,Hwang, Chyuan-Der,Chang, Chun-Wei,Yang, Chun-Tzu,Hwang, Der-Ren
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p. 10479 - 10486
(2007/10/03)
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- Enantioselective addition of trimethylsilyl cyanide to aldehydes catalysed by bifunctional BINOLAM-AlCl versus monofunctional BINOL-AlCl complexes
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A highly enantioselective cyanation of aldehydes takes place by using a bifunctional catalyst derived from 3,3′-bis(diethylaminomethyl) substituted binaphthol (BINOLAM) and dimethylaluminium chloride. The addition is of wide scope and runs best in toluene at temperatures ranging from -20 to -40°C, in the presence of 4 A? MS and triphenylphosphine oxide as additives. The (R)- or (S)-cyanohydrins result when using (S)- or (R)-BINOLAM-AlCl complexes, respectively. The valuable ligand can be recovered by simple extractive work-up and recycled without loss of efficiency (both in terms of chemical and stereochemical yields). This methodology is applied to the Shibasaki synthesis of epothilone A. All the evidence available for the BINOLAM-AlCl enantioselective addition of TMSCN to aldehydes call for the intervention of a hydrocyanation reaction, addition of a catalytic amount of hydrogen cyanide, generated in situ, to an aldehyde, followed by O-silylation. In order to determine the role of the basic amino groups of BINOLAM, comparative studies are carried out with the monofunctional 1,1′-binaphthol-derived complex BINOL-AlCl. Graphical Abstract.
- Casas, Jesús,Nájera, Carmen,Sansano, José M.,Saá, José M.
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p. 10487 - 10496
(2007/10/03)
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- Oxovanadium(V)-catalyzed enantioselective Meerwein-Ponndorf-Verley cyanation of aldehydes using acetone cyanohydrin
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Oxovanadium(V)(salen) complex was found to be a promising catalyst for asymmetric MPV cyanation of aliphatic aldehydes. Oxovanadium(V)(salen) complex 4 was found to catalyze Meerweina€"Ponndorfa€" Verley cyanation of aliphatic aldehydes with good to high
- Watanabe, Akira,Matsumoto, Kazuhiro,Shimada, Yuya,Katsuki, Tsutomu
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p. 6229 - 6233
(2007/10/03)
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- Preparation of polystyrene-bound dichlorotitanium dialkoxide and its application as a polymer-supported Lewis acid catalyst in organic syntheses
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Polymer-supported dichlorotitanium dialkoxide was readily prepared from polystyrene-bound α-glycol and dichlorotitanium diisopropoxide. When we employed it as an immobilized Lewis acid catalyst, several fundamental and important Lewis acid-catalyzed react
- Fujita, Ken-Ichi,Muraki, Takahito,Hashimoto, Shigeru,Oishi, Akihiro,Taguchi, Yoichi
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p. 2097 - 2098
(2007/10/03)
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- O-Protected 3-hydroxy-oxazolidin-2,4-diones: Novel precursors in the synthesis of α-hydroxyhydroxamic acids
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O-Protected 3-hydroxyoxazolidin-2,4-diones have been prepared in a novel one-pot reaction by subsequent treatment of cyanohydrins with 1,1′-carbonyldiimidazole and O-protected hydroxylamines followed by acidic hydrolysis of the intermediate 4-imino-oxazolidin-2-ones. Decarbonylation of O-protected 3-hydroxyoxazolidin-2,4-diones by catalytic amounts of sodium methoxide, lithium hydroxide, sodium carbonate and caesium carbonate in methanol afforded O-protected α-hydroxyhydroxamic acids in excellent yields. Their deprotection provided a series of novel α-hydroxyhydroxamic acids.
- Kurz, Thomas,Widyan, Khalid
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p. 2023 - 2027
(2007/10/03)
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- Design and synthesis of novel imidazo[1,2-a]quinoxalines as PDE4 inhibitors
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New imidazo[1,2-a]quinoxaline derivatives have been synthesised by condensation of an appropriate α-aminoalcohol with a quinoxaline followed by intramolecular cyclisation and nucleophilic substitutions. Their phosphodiesterase inhibitory activities have b
- Deleuze-Masquefa, Carine,Gerebtzoff, Gregori,Subra, Guy,Fabreguettes, Jean-Roch,Ovens, Annabel,Carraz, Maelle,Strub, Marie-Paule,Bompart, Jacques,George, Pascal,Bonnet, Pierre-Antoine
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p. 1129 - 1139
(2007/10/03)
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- Cyanobenzoylation and hydrocyanation of aldehydes with benzoyl cyanide using no catalyst
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(Matrix presented) In the presence of MS 4A in DMSO, cyanobenzoylation of various aldehydes with benzoyl cyanide proceeded very smoothly to give the corresponding cyanohydrin benzoates in high to excellent yields without an acid or a base. On the other hand, reaction of aldehydes with BzCN in DMSO-H2O also occurred readily to afford the corresponding free cyanohydrins exclusively.
- Watahiki, Tsutomu,Ohba, Sayoko,Oriyama, Takeshi
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p. 2679 - 2681
(2007/10/03)
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- BINOLAM, a recoverable chiral ligand for bifunctional enantioselective catalysis: The asymmetric synthesis of cyanohydrins
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(Matrix presented) A new bifunctional catalytic system based on a monometallic aluminum complex is used for the efficient enantioselective cyanation of aldehydes. The ligand (S)- or (R)-2,2′-bis(diethylaminomethyl)-substituted binaphthol (BINOLAM) used is
- Casas, Jesus,Najera, Carmen,Sansano, Jose M.,Saa, Jose M.
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p. 2589 - 2592
(2007/10/03)
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- 1,2-Diphenylethylenediamine linked chiral Ti(IV) complex - A new entry to the highly enantioselective silylcyanation of aliphatic and aromatic aldehydes
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Highly enantioselective silylcyanation of aliphatic and aromatic aldehydes was achieved by using a 1,2-diphenylethylenediamine linked chiral Ti(IV) complex as the catalyst.
- Chang, Chun-Wei,Yang, Chun-Tzu,Hwang, Chyuan-Der,Uang, Biing-Jiun
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- P(MeNMCH2CH2)3N: An effective catalyst for trimethylsilycyanation of aldehydes and ketones
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The title non-ionic phosphazane base promotes the trimethylsilycyanation of alkyl and alkyl aldehydes and ketones in moderate to high yields at room temperature. 29Si-NMR spectral evidence for the intermediacy of a phosphazane phosphorus-silicon adduct is presented.
- Wang, Zhigang,Fetterly, Brandon,Verkade, John G
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p. 161 - 166
(2007/10/03)
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- Highly enantioselective cyanosilylation of aldehydes catalyzed by a Lewis acid-Lewis base bifunctional catalyst
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A new bifunctional asymmetric catalyst containing a Lewis acid and a Lewis base (1) was developed and applied to the catalytic asymmetric cyanosilylation of aldehydes. The products were obtained generally with excellent enantiomeric excess. The experiment
- Hamashima, Yoshitaka,Sawada, Daisuke,Nogami, Hiroyuki,Kanai, Motomu,Shibasaki, Masakatsu
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p. 805 - 814
(2007/10/03)
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- Attempted enantiotopic group selective cyanohydrin formation from α-alkoxy aldehydes by double stereodifferentiation
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Enantiotopic group selectivity can result from the competition between substrate and reagent double stereodifferentiation. We have examined this approach for enantioselective hydrocyanation of racemic α-alkoxy aldehydes (e.g., 2-(phenylmethoxy)heptanal (1)). Reaction of 1 with TMSCN mediated by chiral nonracemic alkoxy Ti(IV) reagents under conditions known to be reasonably enantioface selective in reactions with achiral aldehydes, proceeded with very low enantiotopic group selectivity (2·OEt2. High diastereoselectivity was also observed using achiral and chiral TiCN adducts in place of TMSCN. Although the putative TiCN adducts obtained from nonracemic alkoxy Ti(IV) reagents are implicated in enantioface selective hydrocyanation, these reagents were not enantiotopic group selective under these conditions and showed no evidence of double stereodifferentiation. The use of nonracemic bisoxazoline ligands for Mg(II) was also ineffective.
- Ward, Dale E.,Sales, Marcelo,Hrapchak, Matthew J.
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p. 1775 - 1785
(2007/10/03)
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- Zr(OBut)4 as an effective promoter for the Meerwein-Ponndorf-Verley alkynylation and cyanation of aldehydes: Development of new asymmetric cyanohydrin synthesis
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Zr(OBut)4 can serve as an effective promoter for the Meerwein-Ponndorf-Verley alkynylation of aldehydes and also facilitate MPV type cyanide transfer to aldehyde carbonyls with commercially available acetone cyanohydrin under mild conditions. Based on this finding, a new procedure for asymmetric cyanohydrin synthesis has been developed employing (4R,5R)-2,2-dimethyl-α,α,α′,α′-tetraph enyl-1,3-dioxolane-4,5-dimethanol (TADDOL, 6) as a chiral ligand. For instance, sequential treatment of CH2Cl2 solution of 6 (1 equiv.) with Zr(OBut)4 (1 equiv.) and acetone cyanohydrin (2 equiv.) at room temperature for 1 h, and subsequent reaction with 3-phenylpropanal at -40°C for 7.5 h resulted in formation of the corresponding cyanohydrin 5g [R=Ph(CH2)2] in 63% isolated yield with 85% ee. The scope and limitations of this method have been clarified with various aldehydes as substrates.
- Ooi, Takashi,Miura, Tomoya,Takaya, Keisuke,Ichikawa, Hayato,Maruoka, Keiji
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p. 867 - 873
(2007/10/03)
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