• Title/Summary/Keyword: Chiral aldehyde

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Asymmetric Cyanosilylation of Aldehydes by Chiral Ti-TADDOL Complex

  • Kim, Sung-Soo;Kwak, Ju-Myung;Rajagopal, Gurusamy
    • Bulletin of the Korean Chemical Society
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    • v.27 no.10
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    • pp.1638-1640
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    • 2006
  • A variety of chiral cyanohydrins were readily prepared from aldehydes with TMSCN under the influence of chiral titanium complex formed in situ from $Ti(O^iPr)_4$/TADDOL(I) in the presence of $Ph_3PO$ as additive. The double activation method produces trimethylsilylethers in excellent yield (95%) with moderate enantiomeric excess.

Enantioselective Recognition of Amino Alcohols and Amino Acids by Chiral Binol-Based Aldehydes with Conjugated Rings at the Hydrogen Bonding Donor Sites

  • Kim, Ji-Young;Nandhakumar, Raju;Kim, Kwan-Mook
    • Bulletin of the Korean Chemical Society
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    • v.32 no.4
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    • pp.1263-1267
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    • 2011
  • Novel binol-based uryl and guanidinium receptors having higher ring conjugation at the periphery of the hydrogen bonding donor sites have been synthesized and utilized to study the enantioselective recognition of 1,2-aminoalcohols and chirality conversion of natural amino acids via imine bond formation. There is a remarkable decrease in the stereoselectivites as the conjugation increases at the periphery of hydrogen bonding donor sites. The guanidinium-based receptors show more selectivity towards the amino alcohol than that of the uryl based ones due to its charge reinforced hydrogen bonds. The conversion efficiency of L-amino acids to Damino acids by the uryl-based receptors is higher than that of the guanidinium-based ones.

The Interaction of Chiral Amino Thiols with Organozinc Reagents and Aldehydes: A Mechanism of Amino Thiol-Catalyzed Addition of Organozinc Reagents to Aldehydes

  • 강자효;김진범;김지영;이덕환
    • Bulletin of the Korean Chemical Society
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    • v.19 no.4
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    • pp.475-481
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    • 1998
  • Details of various equilibria involved in the reactions of oxaza- and thiazazincolidine catalysts, generated from either β-amino alcohol or β-amino thiol, with aldehyde were studied by colligative measurements. The results indicated that the coordination of diethylzinc prior to the coordination of aldehyde is essential for high enantioselectivity of the thiol catalyzed reaction. The probable origin of asymmetric nonlinearity is also presented.

Enantioselective Reformatsky Reaction Using Cinchona Alkaloids as Chiral Ligands (Cinchona 알칼로이드를 키랄 리간드로 이용한 비대칭 Reformatsky 반응)

  • Park, Doo-Han;Choi, Ho-Jin;Lee, Sang-Gi
    • Journal of the Korean Chemical Society
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    • v.47 no.6
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    • pp.597-600
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    • 2003
  • Cinchona alkaloids (1-4) were used as chiral ligands for the enantioselective Reformatsky reactions. The order of addition of the Reformatsky reagent to ligands was the important factors for the chiral induction. The ratio of Reformatsky reagent to ligand and aldehyde was also effected on the reaction yields.

Highly Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by Novel Chiral tert-Amino Alcohols

  • Zhang, Cong-Hai;Yan, Sheng-Jiao;Pan, Sheng-Qiang;Huang, Rong;Lin, Jun
    • Bulletin of the Korean Chemical Society
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    • v.31 no.4
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    • pp.869-873
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    • 2010
  • A series of novel chiral tert-amino alcohols 4a-h derived from enantiomerically pure phenylalanine were synthesized efficiently and used as chiral ligands in the catalytic enantioselective ethylation of aldehydes with diethylzinc (diethylzinc-to-aldehyde addition). The use of 10 mol % of the amino alcohols led to the corresponding sec-alcohols with excellent enantioselectivities (up to 100% ee) and high yields.