New polymer anchored chiral amino oxazolines as effective catalysts for enantioselective addition of diethylzinc to aldehydes
作者:Nadim S Shaikh、Vishnu H Deshpande、Ashutosh V Bedekar
DOI:10.1016/s0040-4039(02)01139-5
日期:2002.8
The application of a new type of polymer anchored chiral amino-oxazolinyl ligand as catalyst for the enantioselectiveaddition of diethylzinc to aldehydes is reported. The catalyst is effective at a low ligand concentration and can be reused with minimal loss of activity.
Chiral ligands derived from abrine. Part 7: Effect of O, S, N in aromatic ring substituents at C-1 on enantioselectivity induced by tetrahydro-β-carboline ligands in diethylzinc addition to aldehydes
The effect of O, S and N atoms in aromatic ring substituents at C-1 position of tetrahydro-β-carboline ligands on the enantioselectivity of diethylzincadditions to benzaldehyde was studied when esters or tertiary alcohol functions were present at C-3. A mechanism is proposed to explain why the ester ligands 2c and 2d, in which the pyridyl N atom is at C′-2 in 2c and at C′-3 in 2d, catalyzed the addition
当在C-3处存在酯或叔醇官能团时,研究了四氢-β-咔啉配体的C-1位芳香环取代基中的O,S和N原子对二乙基锌加成苯甲醛的对映选择性的影响。提出了一种机制来解释为什么吡啶基N原子位于2c的C'-2和位于2d的C'-3的酯配体2c和2d催化二乙基锌与苯甲醛的加成反应而形成(R) -和(S1-苯基-1-丙醇的β-对映体。还提出了一种解释,即在添加二乙基锌期间,叔醇3c诱导的中等对映选择性与3d诱导的非常小的对映选择性(在C-1处具有3-吡啶基功能)有关。C-1处的-CH 2 - t -Bu取代基导致很高的对映选择性。
Influences of Electronic Effects and Anions on the Enantioselectivity in the Oxazaborolidine-Catalyzed Asymmetric Borane Reduction of Ketones
作者:Xu、Wei、Zhang
DOI:10.1021/jo048959i
日期:2004.10.1
influence of electronic effects on the enantioselectivity of the oxazaborolidine-catalyzedasymmetricboranereduction of ketones has been observed and investigated with use of para-substituted acetophenones and propiophenones with a variety of functional groups and B-unsubstituted and B-methoxyoxazaborolidines derived from (S)-2-(diphenylhydroxymethyl)pyrrolidine with borane and trimethyl borate as catalysts
Engineering Catalysts for Enantioselective Addition of Diethylzinc to Aldehydes with Racemic Amino Alcohols: Nonlinear Effects in Asymmetric Deactivation of Racemic Catalysts
Correct additions make a difference: Asymmetric deactivation and asymmetric amplification concepts coupled with a high-throughput screening technique provided a successful strategy for designing a highly enantioselective catalytic system by simple combination of a racemic aminoalcohol (rac-DB) and a nonracemic additive (AA). The example in the scheme shows the conversion of 1 into 2 with up to 92
Synthesis and application of 3-substituted (S)-BINOL as chiral ligands for the asymmetric ethylation of aldehydes
作者:Zhi-Guang Zhang、Zhi-Bing Dong、Jin-Shan Li
DOI:10.1002/chir.20842
日期:2010.10
A series of (S)‐BINOL ligands substituted at the 3 position with some five‐membered nitrogen‐containing aromatic heterocycles were effectively prepared and their catalytic abilities were evaluated in the asymmetricaddition of diethylzinc to benzaldehyde in the presence of titanium tetraisopropoxide. Under the optimized reaction conditions, titanium complex of (S)‐3‐(1H‐benzimidazol‐1‐yl)‐1,1′‐bi‐2‐naphthol