Asymmetric synthesis of 3-phenyl-2,3-dihydro-1H-pyrrolo[3,2-b]pyridine-3-carbonitriles catalysed by phase transfer catalyst derived from tert-leucine.

Chiral phase transfer catalysts derived from tert-leucine were synthesized and used in the aymmetric synthesis of 4-azaindoline derivatives. By this method, both enantiomers of corresponding products were obtained in excellent yield (up to 99%) with high enantioselectivity (up to 91% ee) and diastereoselectivity (up to >99: 1 dr).

Carbohydrate-Based Azacrown Ethers in Asymmetric Syntheses

Carbohydrate-based crown ethers represent a special group of chiral phase transfer catalysts. Several derivatives of these macrocycles have been synthesized in our research group. Among these compounds, monoaza-15-crown-5 lariat ethers proved to be effective phase transfer and enantioselective catalysts in certain reactions. Those chiral azacrown ethers incorporating various carbohydrate moieties in the macrocyclic structure are reviewed, which generated asymmetric induction in reactions, such as Michael addition, epoxidation of enones, Darzens condensation and Michael-initiated ring-closure (MIRC) reaction. Effects on the catalytic activity of the structural changes are the focus.

Review on Asymmetric Transformations with Chiral Phase-Transfer Catalysts

This review focuses onasymmetric transformations with Chiral Phase-Transfer Catalysts and its application. Phase-transfer catalysis is practical methodology for organic synthesis. It is possible to achieve highly enantio selective transformations under phase-transfer conditions for a variety of ─C─C─ ─C─O─ and ─C─N─ bond-forming reactions. The asymmetric transformations using modified cinchona alkaloids, chiral spiro ammonium salts and crown ether are among the primary source of effective chiral phase-transfer catalyst, which allows access to enantiomerically pure unnatural amino acids and synthetically useful adducts containing quaternary stereogenic centers. The advantage of this method is its simple experimental procedure, large chiral pool, mild reaction condition, inexpensive, environmentally benign reagent and use of simple and inexpensive reactants. Nowadays, it appears to be the most important synthetic method used in various fields of organic chemistry, and also found widespread industrial applications. This review summarizes the synthesis application, enantio selective transformation of some selected reaction, biological activities and catalytic activities of Phase-transfer catalysis and especial emphasis is given for organo catalysis. In asymmetric organo catalyst, it is possible to obtain chiral organic products in high enantio enriched form by steric hindrance approach method. The advantage of organic molecules as chiral catalysts complements the traditional organo-metallic and biological approaches to asymmetric catalysis.

Enantioselective Benzylation and Allylation of α-Trifluoromethoxy Indanones under Phase-Transfer Catalysis

The organo-catalyzed enantioselective benzylation reaction of α-trifluoromethoxy indanones afforded α-benzyl-α-trifluoromethoxy indanones with a tetrasubstituted stereogenic carbon center in excellent yield with moderate enantioselectivity (up to 57% ee). Cinchona alkaloid-based chiral phase transfer catalysts were found to be effective for this transformation, and both enantiomers of α-benzyl-α-trifluoromethoxy indanones were accessed, depended on the use of cinchonidine and cinchonine-derived catalyst. The method was extended to the enantioselective allylation reaction of α-trifluoromethoxy indanones to give the allylation products in moderate yield with good enantioselectivity (up to 76% ee).

Enantioselective Benzylation and Allylation of α-Trifluoromethoxy Indanones under Phase-Transfer Catalysis

The organo-catalyzed enantioselective benzylation reaction of α-trifluoromethoxy indanones afforded α-benzyl-α-trifluoromethoxy indanones with a tetrasubstituted stereogenic carbon center in excellent yield with moderate enantioselectivity (up to 57% ee). Cinchona alkaloid-based chiral phase transfer catalysts were found to be effective for this transformation, and both enantiomers of α-benzyl-α-trifluoromethoxy indanones were accessed, depended on the use of cinchonidine and cinchonine-derived catalyst. The method was extended to the enantioselective allylation reaction of α-trifluoromethoxy indanones to give the allylation products in moderate yield with good enantioselectivity (up to 76% ee).

Chiral Phase-Transfer Catalysts with Hydrogen Bond: A Powerful Tool in the Asymmetric Synthesis

Asymmetric phase-transfer catalysis has been widely applied into organic synthesis for efficiently creating chiral functional molecules. In the past decades, chiral phase-transfer catalysts with proton donating groups are emerging as an extremely significant strategy in the design of novel catalysts, and a large number of enantioselective reactions have been developed. In particular, the proton donating groups including phenol, amide, and (thio)-urea exhibited unique properties for cooperating with the phase-transfer catalysts, and great advances on this field have been made in the past few years. This review summarizes the seminal works on the design, synthesis, and applications of chiral phase-transfer catalysts with strong hydrogen bonding interactions.

Diastereo- and enantioselective nitro-Mannich reaction of isatin-derived N-Boc ketimines catalyzed by chiral phase-transfer catalysts

A series of 3-substituted 3-amino-oxindoles were constructed in excellent yields (96–99%) with high enantioselectivities (up to 95% ee) and diastereoselectivities (up to 95 : 5 dr) catalyzed by Cinchona alkaloid-derived phase-transfer catalysts.