120409-04-3Relevant academic research and scientific papers
68. Enantio- and Diastereoselective Aldol-Reaction of 2,6-Dimethylphenyl Propionate Using Titanium-Carbohydrate Complexes
Duthaler, Rudolf O.,Herold, Peter,Wyler-Helfer, Susanne,Riediker, Martin
, p. 659 - 673 (2007/10/02)
Chloro(cyclopentadienyl)bis(1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-O-yl)titanium (1) is used for the transmetallation of Li-enolates obtained from propionyl derivatives.While such Ti-enolates of ketones and hydrazones appear to be unreactive, the
Metal complexes containing optically active sugar ligands, a process for their preparation and their use as chiral reactants for synthesis of alcohols and amines
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, (2008/06/13)
Compounds of the forulae I and Ia STR1 in which R1 is a group which can be transferred to carbonyl or imine compounds, for example alkyl, allyl, vinyl or the radical of an enol or enamine, R2 is, for example, cyclopentadienyl, R3 is the radical of an optically active sugar or sugar derivative, Me is Ti, Zr or Hf, x is 0, 1 or 2 and y is 0, 1, 2 or 3, M≈ is Li≈, Na≈, K≈, MgY≈, ZnY≈, CdY≈, HgY, CuY≈ or quaternary ammonium, Y being halogen, are suitable for use as chiral reactants for compounds containing aldehyde, keto and/or N-substituted imine groups.
ACYCLIC STEREOSELECTION-13; ARYL ESTERS: REAGENTS FOR THREO-ALDOLIZATION
Heathcock, Clayton H.,Pirrung, Michael C.,Montgomery, Stephen H.,Lampe, John
, p. 4087 - 4095 (2007/10/02)
Preformed Li enolates of hindered aryl esters condense with aldehydes to give predominantly threo aldols.The method has been explored with esters 3 (DMP propionate), 4 (BHT propionate), 5 (DBHA propionate).DMP propionate reacts with benzaldehyde and α-unbranched aliphatic aldehydes to give threo:erythro ratios of about 6.5:1.However, with α-branched aliphatic aldehydes, ester 3 gives only threo-aldols.BHT propionate and DBHA propionate give only threo-aldols with all aldehydes studied.The DMP aldols may be converted into β-hydroxy acids by simple hydrolysis with KOH in aqueous methanol.BHT aldols cannot be hydrolyzed without retroaldolization.However, these aldols can be reduced to diastereomerically pure 1,3-diols.The DBHA aldols can converted into β-hydroxy acids by a method involving oxidation with ceric ammonium nitrate (CAN) in aqueous acetonitrile.Threo-selectivity is also seen in the condensations of DMP butyrate (15), DBHA butyrate (16), DMP pentenoate (17), and BHT pentenoate (18).The approach has been utilized in a stereoselective synthesis of racemic methyl corynomycolate.
