Organocatalytic Asymmetric Synthesis of Trifluoromethyl-substituted Diarylpyrrolines: Enantioselective Conjugate Cyanation of β-Aryl-β-trifluoromethyl-disubstituted Enones

Pd/Cu-Catalyzed Enantioselective Sequential Heck/Sonogashira Coupling: Asymmetric Synthesis of Oxindoles Containing Trifluoromethylated Quaternary Stereogenic Centers

An asymmetric palladium and copper co-catalyzed Heck/Sonogashira reaction between o-iodoacrylanilides and terminal alkynes to synthesize chiral oxindoles was developed. In particular, a wide range of CF₃ -substituted o-iodoacrylanilides reacted with terminal alkynes, affording the corresponding chiral oxindoles containing trifluoromethylated quaternary stereogenic centers in high yields with excellent enantioselectivities (94-98 % ee). This asymmetric Heck/Sonogashira reaction provides a general approach to access oxindole derivatives containing quaternary stereogenic centers including CF₃ -substituted ones.

Palladium-Catalyzed Suzuki-Miyaura Cross-Coupling of Secondary α-(Trifluoromethyl)benzyl Tosylates

A palladium-catalyzed C(sp³ )-C(sp² ) Suzuki-Miyaura cross-coupling of aryl boronic acids and α-(trifluoromethyl)benzyl tosylates is reported. A readily available, air-stable palladium catalyst was employed to access a wide range of functionalized 1,1-diaryl-2,2,2-trifluoroethanes. Enantioenriched α-(trifluoromethyl)benzyl tosylates were found to undergo cross-coupling to give the corresponding enantioenriched cross-coupled products with an overall inversion in configuration. The crucial role of the CF₃ group in promoting this transformation is demonstrated by comparison with non-fluorinated derivatives.

Organic base-promoted enantioselective electrophilic cyanation of β-keto esters by using chiral phase-transfer catalysts

Highly enantioselective cyanation of β-keto esters using hypervalent iodine(iii) as the electrophilic cyanating reagent induced by cinchona alkaloid-based chiral quaternary ammonium salt was demonstrated. Organic bases, especially DMAP, in the chiral phase-transfer catalysis were used to obtain high ees.

An efficient approach for the construction of trifluoromethylated all-carbon quaternary stereocenters: enantioselective Ni(ii)-catalyzed Michael addition of 2-acetyl azaarene to β,β-disubstituted nitroalkenes

Michael addition of 2-acetyl azaarenes with β,β-disubstituted nitroalkenes afforded chiral compounds in good yields and with excellent enantioselectivities.

Recent developments in asymmetric phase-transfer reactions

Phase-transfer catalysis has been recognized as a powerful method for establishing practical protocols for organic synthesis, because it offers several advantages, such as operational simplicity, mild reaction conditions, suitability for large-scale synthesis, and the environmentally benign nature of the reaction system. Since the pioneering studies on highly enantioselective alkylations promoted by chiral phase-transfer catalysts, this research field has served as an attractive area for the pursuit of "green" sustainable chemistry. A wide variety of asymmetric transformations catalyzed by chiral onium salts and crown ethers have been developed for the synthesis of valuable organic compounds in the past several decades, especially in recent years.