A series of new C₂‐symmetric amino alcohols with multicoordination groups: Promising catalysts for synthesis of both enantiomers in the borane‐mediated reduction of prochiral ketones

Abstract

A series of new C(2)-symmetric amino alcohols with multicoordination groups have been synthesized and successfully applied as catalysts in the borane asymmetric reduction of prochiral ketones in refluxing toluene, providing the corresponding secondary alcohols with up to 90% ee. An unusual temperature-dependent reversal of stereochemistry was also observed.

Asymmetric Organocatalytic Efficiency of Synthesized Chiral β-Amino Alcohols in Ring-Opening of Glycidol with Phenols

“…For example, chiral b-amino alcohols have been used in many reactions as catalysts such as asymmetric addition of organozinc reagents to ketones and aldehydes [4][5][6][7], asymmetric transfer hydrogenation [8,9], reduction of ketones to alcohols [10,11]. Furthermore, the asymmetric ring opening of epoxides by alcohol and thiol nucleophiles were also achieved with Ti(i-OPr) 4 and Sc(OTf) 3 mediated amino alcohols, respectively [12,13].…”

β‐Hydroxyamide‐Based Ligands and Their Use in the Enantioselective Borane Reduction of Prochiral Ketones

“…As important intermediates in the preparation of chiral oxazoline ligands, 25 thiazoline ligands 26,27 and imidazoline ligands, 28,29 many chiral β-hydroxyamides have been synthesized from carboxylic acids and amino alcohols. 30 Considering the potential coordination and H-bond donation ability of β-hydroxyamides, some of them have been applied to asymmetric catalysis as ligands or catalysts. 30 Considering the potential coordination and H-bond donation ability of β-hydroxyamides, some of them have been applied to asymmetric catalysis as ligands or catalysts.…”

“…In addition to developing versatile chiral catalysts, Liu and colleagues reported the synthesis of prolinol-based C 2 -symmetric amino alcohols with multicoordination groups and their application in the catalytic borane-mediated reduction of prochiral ketones. 30 Considering the potential coordination and H-bond donation ability of β-hydroxyamides, some of them have been applied to asymmetric catalysis as ligands or catalysts. 15 There is a continuing interest in the development of new tridentates chiral ligands to be tested in the borane enantioselective reduction of prochiral ketones.…”

Enantioselectivity, swelling and stability of 4-hydroxyprolinol containing acrylic polymer beads in the asymmetric reduction of ketones

“…40,42 The use of the phenyl analogue Ic seems to have advantages in the reduction of 1-(4-nitrophenyl)ethanone 1i, 12 while the derivatives Id-e are good catalysts for the preparation of the trifluoroalcohol 8c. Of all the bi-and tridentate catalysts prepared and tested, [16][17][18][19][20][21] catalyst IV appears to be the most efficient. Catalyst IV 16 performs especially well in the reduction of 2,2,2-trifluoro-1-phenylethanone 4c and 1-(3,5-dinitrophenyl)ethanone (95% ee, data not shown).…”

“…[13][14][15] Also, some C2 and C3 symmetric diphenylprolinol based systems have been evaluated in asymmetric borane reductions. [16][17][18][19][20][21] 0957-4166/$ -see front matter Ó 2011 Elsevier Ltd. All rights reserved. …”