Highly Enantioselective Chlorination of β-Keto Esters and Subsequent SN2 Displacement of Tertiary Chlorides: A Flexible Method for the Construction of Quaternary Stereogenic Centers
摘要:
Highly enantioselective chlorination of beta-oxo esters and subsequent stereospecific substitution of tertiary chlorides are described. Enantioselective chlorination of beta-keto esters and malonates was performed using a chiral Lewis acid catalyst prepared from Cu(OTf)(2) and the newly developed spirooxazoline ligand 2 to yield the desired a-chlorinated products with high enantioselectivity (up to 98% ee). Nucleophilic substitution of the resulting chlorides proceeded smoothly to afford a variety of chiral molecules such as alpha-amino, alpha-allcylthio, and alpha-fluoro esters, without loss of enantiopurity. The results of X-ray crystallographic analysis proved that Walden inversion occurs at the chlorinated tertiary carbon center. These results supported the fact that the substitution proceeds via an S(N)2 mechanism.
Highly Enantioselective Chlorination of β-Keto Esters and Subsequent SN2 Displacement of Tertiary Chlorides: A Flexible Method for the Construction of Quaternary Stereogenic Centers
摘要:
Highly enantioselective chlorination of beta-oxo esters and subsequent stereospecific substitution of tertiary chlorides are described. Enantioselective chlorination of beta-keto esters and malonates was performed using a chiral Lewis acid catalyst prepared from Cu(OTf)(2) and the newly developed spirooxazoline ligand 2 to yield the desired a-chlorinated products with high enantioselectivity (up to 98% ee). Nucleophilic substitution of the resulting chlorides proceeded smoothly to afford a variety of chiral molecules such as alpha-amino, alpha-allcylthio, and alpha-fluoro esters, without loss of enantiopurity. The results of X-ray crystallographic analysis proved that Walden inversion occurs at the chlorinated tertiary carbon center. These results supported the fact that the substitution proceeds via an S(N)2 mechanism.
Chiral 2-Amino Alcohol Derivatives Catalyze the Enantioselective α-Chlorination of β-Ketoesters
作者:Baohua Zhang、Ruixia Guo、Sijie Liu、Lanxiang Shi、Xiaoyun Li
DOI:10.5012/bkcs.2014.35.6.1759
日期:2014.6.20
The enantioselective $\alpha}$-chlorination of cyclic $\beta}$-ketoesters catalyzed by chiral 2-aminoalcohol derivatives (2f) has been developed. For the optically active $\alpha}$-chlorinated products, the isolated yields are in the range of 85-94% and the enantiomeric excesses are up to 84% ee.
Abstract An iron(III)-BPsalan complex was found to efficiently catalyze the asymmetric chlorination reaction of cyclic β-ketoesters and N-Boc oxindoles, affording the corresponding chlorinated products in high yield and up to 92% ee with NCS as chlorination reagent under mild reaction conditions. An iron(III)-BPsalan complex was found to efficiently catalyze the asymmetric chlorination reaction of
Catalytic enantioselective chlorination of cyclic β-keto esters in the presence of chiral Pd(II) complexes
作者:Young Ku Kang、Hee Hun Kim、Kwang Oh Koh、Dae Young Kim
DOI:10.1016/j.tetlet.2012.05.064
日期:2012.7
The catalyticenantioselective electrophilic chlorination promoted by chiral palladium complexes is described. The treatment of β-keto esters with 2,3,4,5,6,6-hexachlorocyclohex-2,4-dienone as chlorine source under mild reaction conditions afforded the corresponding α-chlorinated β-keto esters with excellent enantioselectivities (up to 94% ee).