Development of novel optically active two-canter phase-transfer catalysts for enantioselective synthesis of -amino acid

New optically active bis-quaternary ammonium salts were synthesized and applied to catalytic asymmtric alkylation of tert-butyl glycinate benzophenone Schiff base to provide a chiral a-amino acid derivative with 54% ee

Amine-Catalyzed Decarboxylative Aldol Reaction of β-Ketocarboxylic Acids with Trifluoropyruvates

Decarboxylative aldol reaction of aliphatic carboxylic acids is a useful method for C–C bond formation because carboxylic acids are an easily available class of compounds. In this study, we found that the decarboxylative aldol reaction of tertiary β-ketocarboxylic acids and trifluoropyruvates proceeded smoothly to yield the corresponding aldol products in high yields and with high diastereoselectivity in the presence of a tertiary amine catalyst. In this reaction, we efficiently constructed a quaternary carbon center and an adjacent trifluoromethylated carbon center. This protocol was also extended to an enantioselective reaction with a chiral amine catalyst, and the desired product was obtained with up to 73% enantioselectivity

Organocatalytic asymmetric fluorination of α-chloroaldehydes involving kinetic resolution

In a previous study it was shown that the enantioselective α-fluorination of racemic α-chloroaldehydes with a chiral organocatalyst yielded the corresponding α-chloro-α-fluoroaldehydes with high enantioselectivity. It was also revealed that kinetic resolution of the starting aldehydes was involved in this asymmetric fluorination. This paper describes the determination of the absolute stereochemistry of a resulting α-chloro-α-fluoroaldehyde. Some information about the substrate scope and a possible reaction mechanism are also described which shed more light on the nature of this asymmetric fluorination reaction

Highly Enantioselective Synthesis of Cyclopropylamine Derivatives via Ru(II)-Pheox-Catalyzed Direct Asymmetric Cyclopropanation of Vinylcarbamates

The Ru(II)-Pheox-catalyzed asymmetric cyclopropanation of vinylcarbamates with diazoesters resulted in the corresponding cyclopropylamine derivatives in high yield and excellent diastereoselectivity (up to 96:4) and enantioselectivity (up to 99% ee)

Highly Enantioselective Chlorination of β-Keto Esters and Subsequent S_N2 Displacement of Tertiary Chlorides: A Flexible Method for the Construction of Quaternary Stereogenic Centers

Highly enantioselective chlorination of β-oxo esters and subsequent stereospecific substitution of tertiary chlorides are described. Enantioselective chlorination of β-keto esters and malonates was performed using a chiral Lewis acid catalyst prepared from Cu­(OTf)₂ and the newly developed spirooxazoline ligand <b>2</b> to yield the desired α-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 α-amino, α-alkylthio, and α-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_N2 mechanism

Highly Enantioselective Chlorination of β-Keto Esters and Subsequent S_N2 Displacement of Tertiary Chlorides: A Flexible Method for the Construction of Quaternary Stereogenic Centers

Highly enantioselective chlorination of β-oxo esters and subsequent stereospecific substitution of tertiary chlorides are described. Enantioselective chlorination of β-keto esters and malonates was performed using a chiral Lewis acid catalyst prepared from Cu­(OTf)₂ and the newly developed spirooxazoline ligand <b>2</b> to yield the desired α-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 α-amino, α-alkylthio, and α-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_N2 mechanism

Highly Enantioselective Chlorination of β-Keto Esters and Subsequent S_N2 Displacement of Tertiary Chlorides: A Flexible Method for the Construction of Quaternary Stereogenic Centers

Highly enantioselective chlorination of β-oxo esters and subsequent stereospecific substitution of tertiary chlorides are described. Enantioselective chlorination of β-keto esters and malonates was performed using a chiral Lewis acid catalyst prepared from Cu­(OTf)₂ and the newly developed spirooxazoline ligand <b>2</b> to yield the desired α-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 α-amino, α-alkylthio, and α-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_N2 mechanism