Axially chiral dicarboxylic acid catalyzed activation of quinone imine ketals: enantioselective arylation of enecarbamates.

The synthetic utility of quinone imine ketals in the context of asymmetric catalysis was disclosed for the first time. By expanding the utility of chiral Brønsted acid catalysis to the electrophilic activation of quinone imine ketals, we succeeded in the development of highly enantioselective arylation of encarbamates to give α-amino-β-aryl ethers wherein quinone imine ketals act as functionalized aromatic ring surrogate. Further transformations of the products were also examined to establish procedures to provide chiral β-aryl amines and α-aryl esters.

Catalytic asymmetric three-component 1,3-dipolar cycloaddition of aldehydes, hydrazides, and alkynes.

Catalytic asymmetric 1,3-dipolar cycloadditions offer expeditious ways to afford synthetically important chiral heterocycles. Although a variety of 1,3-dipoles can be employed in this context, the use of acyclic azomethine imines as a facile means to give chiral pyrazolines and pyrazolidines remains completely unexplored. We report herein the first catalytic asymmetric 1,3-dipolar cycloaddition of terminal alkynes with acyclic azomethine imines generated in situ from the corresponding aldehydes and hydrazides, which was realized using Cu(I)/pybox and axially chiral dicarboxylic acid cocatalysts.

Effect of chiral diene ligands in rhodium-catalyzed asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds.

Asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of the addition products with high enantioselectivity (96->99.5% ee). The diene ligand was proved to be essential for the formation of the addition products, while the use of a bisphosphine ligand mainly gave the cine-substitution product.