- ASYMMETRIC TRANSCYANOHYDRINATION
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Transcyanohydrination, the reaction between an aldehyde and acetone cyanohydrin to give the cyanohydrin of the aldehyde, catalyzed by cyclo((S)-phenylalanyl-(S)-histidyl) gives the product with optical yield up to 63 percent from some aromatic and aliphatic aldehydes.The reaction catalyzed by (S)-α-dimethylamino-ε-caprolactam gives the product with optical yield of 15 - 25 percent from aliphatic aldehydes.
- Kobayashi, Yoshiyuki,Hayashi, Hiroaki,Miyaji, Koji,Inoue, Shohei
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- Highly active bifunctional salenTi(IV) catalysts for asymmetric cyanosilylation of aldehydes and TMSCN
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A novel enantiopure salen ligand bearing a diphenylphosphine oxide on the 3-position of one aromatic ring was synthesized and combined with Ti(Oi-Pr) 4 as a monometallic bifunctional catalyst for asymmetric cyanosilylation reaction of aldehydes with trimethylsilyl cyanide (TMSCN). The catalyst system exhibited excellent activity and moderate enantioselectivity. The addition of TMSCN to 4-nitrobenzaldehyde in the presence of 1 mol% catalyst loading could complete within 10 min at ambient temperature. An intramolecularly cooperative catalysis was observed in this system wherein the central metal Ti(IV) is suggested to play a role of Lewis acid to activate aldehydes while the appended diphenylphosphine oxide worked as Lewis base to activate TMSCN.
- Wen, Ye Qian,Ren, Wei Min,Lu, Xiao Bing
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scheme or table
p. 1285 - 1288
(2012/01/17)
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- Chiral linear polymers bonded alternatively with salen and 1,4-dialkoxybenzene: Synthesis and application for Ti-catalyzed asymmetric TMSCN addition to aldehydes
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The synthesis of chiral linear polymers 1a-b having salen and 1,4-dioctyloxybenzene as alternate segments has been accomplished. The GPC analysis showed the molecular weights corresponding to ca. 15 (Mw = 10,999, Mn = 9165 and PDI = 1.20) repeating units for 1a and ca. 8 (Mw = 8547, Mn = 7883 and PDI = 1.08) repeating units for 1b. Polymers 1a-b have been studied with Ti(OiPr)4 as a recyclable catalyst for the asymmetric addition of TMSCN to aldehydes while the selectivity of the polymer catalyst is identical to that of the monomer. The reactions are efficient affording the cyanohydrins with up to 88% ee. The selectivity of the polymer based catalyst 9a is found to be the same to that of the monomer 10a. The reaction provides the advantages of simplified product isolation and easy recovery and recyclability of polymer catalyst 9a without any loss of activity or selectivity.
- Sakthivel, Sekarpandi,Punniyamurthy, Tharmalingam
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experimental part
p. 2834 - 2840
(2011/03/19)
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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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- A new (R)-hydroxynitrile lyase from Prunus mume: Asymmetric synthesis of cyanohydrins
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A new hydroxynitrile lyase (HNL) was isolated from the seed of Japanese apricot (Prunus mume). The enzyme has similar properties with HNL isolated from other Prunus species and is FAD containing enzyme. It accepts a large number of unnatural substrates (benzaldehyde and its variant) for the addition of HCN to produce the corresponding cyanohydrins in excellent optical and chemical yields. A new HPLC based enantioselective assay technique was developed for the enzyme, which promotes the addition of KCN to benzaldehyde in a buffered solution (pH=4.5).
- Nanda, Samik,Kato, Yasuo,Asano, Yasuhisa
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p. 10908 - 10916
(2007/10/03)
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- Highly enantioselective cyanosilylation of aldehydes catalyzed by novel β-amino alcohol-titanium complexes
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The β-amino alcohol 1b-Ti(Oi-Pr)4 complex has been shown to catalyze the enantioselective cyanosilylation of aldehydes efficiently. In the presence of 5 mol % of 1b-Ti(Oi-Pr)4 complex catalyst, the aromatic, conjugated, heteroaromatic, and aliphatic aldehydes were converted to their corresponding trimethylsilyl ethers of cyanohydrins in 90-99% yields with up to 94% ee under mild conditions.
- Li, Yan,He, Bin,Qin, Bo,Feng, Xiaoming,Zhang, Guolin
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p. 7910 - 7913
(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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- Development of a family of β-amino alcohol ligands with two stereocenters for highly efficient enantioselective trimethylsilylcyanation of aldehydes
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The asymmetric addition of Me3SiCN to aldehydes catalyzed by titanium(IV) complexes of N-sulfonylated derivatives of β-amino alcohols gave excellent ee's up to 96% ee.
- You,Gau,Choi
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p. 1963 - 1964
(2007/10/03)
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- Asymmetric amino acid synthesis: Mitsunobu reaction on chiral cyanohydrins
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BOC(SES)NH was reacted with chiral cyanohydrins using the Mitsunobu reaction to give good yields of protected α-aminonitriles, which were converted to chiral amino and imino acids.
- Decicco, Carl P.,Grover, Paul
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p. 529 - 530
(2007/10/03)
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- Ueber die erste rekombinante Hydroxynitril-Lyase und ihre Anwendung in der Synthese von (S)-Cyanhydrinen
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Keywords: Asymmetrische Synthesen; (S)-Cyanhydrine; Enzymkatalyse; Lyasen
- Foerster, Siegfried,Roos, Juergen,Effenberger, Franz,Wajant, Harald,Sprauer, Achim
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p. 493 - 494
(2007/10/03)
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- Asymmetric synthesis of tetronic acids by Blaise reaction of protected optically active cyanohydrins
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An asymmetric synthesis of tetronic acids is described, involving the Blaise reaction of Reformatsky reagents with silyl-protected optically active cyanohydrins, which were prepared by an enzyme-catalysed method.
- Duffield, Jonathan J.,Regan, Andrew C.
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p. 663 - 666
(2007/10/03)
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- Aliphatic (S)-Cyanohydrins by Enzyme Catalyzed Synthesis
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The enzyme catalyzed synthesis of aliphatic (S)-cyanohydrins has been accomplished for the first time by application of a hydroxynitrile lyase from leaves of Hevea brasiliensis.The optical purities of (S)-cyanohydrins obtained are in a range between 60 - 97percent.
- Klempier, Norbert,Griengl, Herfried,Hayn, Marianne
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p. 4769 - 4772
(2007/10/02)
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- Enzyme-Catalysed Synthesis of Optically Active Aliphatic Cyanohydrins
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The enantioselective preparation of aliphatic (R)-cyanohydrins was studied using powdered almond meal, a rich source of mandelonitrile lyase, as a catalyst in organic solvent.The feasibility of powdered almond meal as a catalyst was compared to that of a purified enzyme preparation.
- Huuhtanen, Tuomas T.,Kanerva, Liisa T.
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p. 1223 - 1226
(2007/10/02)
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- The Cyclic Dipeptide cyclo as a Catalyst for Asymmetric Addition of Hydrogen Cyanide to Aldehydes
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cyclo (cyclo, 1) catalyzes the addition of hydrogen cyanide to benzaldehyde in toluene at -20 deg C to afford (R)-mandelonitrile with enantiomeric excess of 97 percent in high yield. cyclo gives (S)-mandelonitrile. cyclo (1) exhibits a broad substrate specificity, and a variety of aldehydes (3a-r) such as m-methoxybenzaldehyde (3c), 6-methoxy-2-naphthaldehyde (3k), and isobutyraldehyde (3o) similarly afforded the corresponding cyanohydrins with high enantiopurities (97 percent ee for 3c, 93 percent ee for 3k, 71 percent ee for 3o). (R)-Mandelonitrile thus obtained was successfully converted to various chiral synthons such as mandelic acid (7), methyl mandelate (8), and 2-amino-1-phenylethanol (9) without any racemization.
- Tanaka, Kenzo,Mori, Atsunori,Inoue, Shohei
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p. 181 - 185
(2007/10/02)
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- Cyclo-((S)-leucyl-(S)-histidyl). A Catalyst for Asymmetric Addition of Hydrogen Cyanide to Aldehydes
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Asymmetric addition of hydrogen cyanide to various aldehydes in the presence of a catalytic amount of cyclo-((S)-leucyl-(S)-histidyl) affords the corresponding cyanohydrins in moderate to good optical yields.The reaction of benzaldehyde with hydrogen cyanide gives (S)-2-hydroxy-2-phenylacetonitrile (85percent, 55percent ee) whose stereochemistry is found to be opposite to our previous result using cyclo-((S)-phenylalanyl-(S)-histidyl).
- Mori, Atsunori,Ikeda, Yoshitaka,Kinoshita, Koichi,Inoue, Shohei
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p. 2119 - 2122
(2007/10/02)
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