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Relevant academic research and scientific papers

Process for preparing esters and organic halides

A process for preparing esters and organic halides, which comprises reacting - a salt having a melting point of less than 100°C (at 1 bar) and of the formula ???????? (K+)n X (COO-)n, in which K+ is an organic cation, X (COO-)n is an organic anion having an n-valent organic group X which is substituted by n carboxylate groups COO-, and n is 1, 2 or 3, - with an organic halogen compound (Hal)mY, in which Hal is a halogen atom, Y is an m-valent organic group, and m is 1, 2 or 3, to give an ester and a halide K+ Hal-.

Ruthenium- and lipase-catalyzed inversion of l-lactates

The ruthenium catalyzed inversion of l-lactic acid esters in the presence of Novozym 435 is described which give d-lactates in good yields and with >99% ee. 2012 Elsevier Ltd. All rights reserved.

Efficient and highly enantioselective Rh-catalyzed hydrogenations of unsaturated lactate precursors with chiral bisphospholanes as ligands

The current invention relates to an asymmetric hydrogenation process of prochiral α-acetoxy acrylic acid esters for the synthesis of enantiopure lactic acid esters by the use of Rh-catalyzed bisphospholane ligands in a unit using an autoclave, and a distillation process. In a first process step α-acetoxy acrylic acid esters (1) and Rh-catalyzed bisphospholane ligands are dissolved in a solvent as substrate solution, in a second process step the substrate solution is added to an evacuated autoclave, in a third process step H2 is fed into the autoclave, in a fourth process step the asymmetric hydrogenation reaction is carried out under H2-pressure, and in a fifth process step the reaction product composed of solvent, lactic acid esters (2), remaining α-acetoxy acrylic acid esters (1) and Rh-catalyzed bisphospholane ligands is transferred into a distillation unit, is being distilled and enantiopure lactic acid esters (2) are separated from solvent, α-acetoxy acrylic acid esters (1) and Rh-catalyzed bisphospholane ligands. In this process propylene carbonate is used as solvent in the first process step, and the distillation is performed in a Spaltrohrkolonne in the fifth process step.

Highly enantioselective acylation of rac-alkyl lactates using Candida antarctica lipase B

By using Candida antarctica lipase B under mild conditions, the highly enantioselective acylation of alkyl (R)-lactate from racemic mixture with vinyl alkanoate has been accomplished. In this research effects of the organic solvent, the alkyl chain length of the alkyl lactates and of the vinyl alkanoates, and the reaction temperature on the enantiomeric excess as well as the reaction rate, were investigated. In all cases, only alkyl (R)-lactate was stereoselectively acylated at >99.5% ee. The lipase-catalyzed acylation rate of the alkyl lactates was affected by the nature of the organic solvents, but showed no correlation to log P of the solvent. The lipase-catalyzed acylation rate of the alkyl lactates was enhanced by increasing the chain length of the vinyl alkanoate from acetyl to butanoyl and by raising the reaction temperature to 65°C. Finally, the lipase-catalyzed acylation and subsequent vacuum distillation successfully provided both butyl (R)-O-butanoyllactate and butyl (S)-lactate in excellent yields (48%) and enantioselectivities (>99.5% ee) on a large scale. It is expected that the present method will prove to be more efficient in achieving the chiral resolution of racemic alkyl lactate than other conventional methods in terms of environmental friendliness and simplicity.

New ferrocenyl ligands with broad applications in asymmetric catalysis

A new synthetic approach allows the synthesis of taniaphos- analogous ligands 2 with inverted α configuration (Sp, αS). This new class of ferrocenyl ligands displays excellent enantioselectivity and enhanced reactivity in several types of asymmetric hydrogenation reactions (e.g. 1→).

Synthesis of a new class of chiral 1,5-diphosphanylferrocene ligands and their use in enantioselective hydrogenation

A new family of ferrocenylphosphane ligands has been prepared. Their flexible synthesis allows many structural modifications. The asymmetric induction of these ligands was examined in the hydrogenation of functionalized C=C, C=O, and C=N bonds. The enantioselectivity of the reaction was strongly dependent on the substituent R at the position α to the ferrocene moiety. In many cases, both enantiomeric β-hydroxyesters of the reduction product can be obtained by simply replacing a dimethylamino group in the ligand with a methyl group.

Stereoselective substitution of α-aminoalkylferrocenes with diorganozincs. A fast synthesis of new chiral FERRIPHOS ligands for asymmetric catalysis

A direct stereoselective substitution of α-aminoalkylferrocenes of type 3 with organozinc reagents provides chiral ferrocenes which can be converted to the FERRIPHOS ligands of type 1 in a one-pot procedure. These FERRIPHOS ligands have been used for the Rh-catalyzed asymmetric hydrogenation of an enol acetate with 94.9% ee.