Synthesis of Novel Bisoxazoline Ligands for the Enantioselective Diels-Alder Reaction

Four novel bisoxazoline ligands 8a-d were synthesized from （S）-amino alcohols and could be formed effective catalysts （up to 77% ee for endo isomer） with Cu（OTf）2 for enantioselective Diels-Alder addition. The facility of the reaction was dependent on the nature of the substituent R in the bisoxazoline ligand.

Highly enantioselective construction of CF_(3) -bearing all-carbon quaternary stereocenters: Chiral spiro-fused bisoxazoline ligands with 1,1'-binaphthyl sidearm for asymmetric Michael-type Friedel-Crafts reaction

A novel class of chiral spiro-fused bisoxazoline ligands possessing a deep chiral pocket was prepared.The developed ligands have been employed in the nickel-catalyzed highly enantioselective Michael-type Friedel-Crafts reaction, affording the products bearing a trifluoromethylated all-carbon quaternary stereocenter with moderate to excellent yields(up to 99%) and good to excellent enantioselectivies(up to> 99.9% ee). Moreover, a proposed model of chiral pocket revealed that the attack of indole from the Re-face of β-CF_(3)-β-disubstituted nitroalkene was favorable.

Enantioselective chlorination of β-keto esters and amides catalyzed by chiral copper(Ⅱ) complexes of squaramide-linked bisoxazoline ligand

Enantioselective chlorination of b-keto esters and amides catalyzed by squaramide-linked bisoxazoline ligand–Cu（OAc）2complexes was investigated. The corresponding chlorinated products were obtained in excellent yields with moderate enantioselectivities. The effect of solvent, temperature, Lewis acid, and ligand structure on the reaction is discussed. This was the first investigation of catalytic asymmetric achlorination of b-keto amides. This study has highlighted that a simple chiral squaramide–oxazoline with cheap Cu（OAc）2 H2 O complexes can catalyze this chlorination.

Copper Catalyzed Asymmetric [4＋2] Annulations of D-A Cyclobutanes with Aldehydes

Copper catalyzed enantioselective [4＋2] annulations of D-A cyclobutanes and aldehydes have been developed. In the presence of a side arm modified chiral bisoxazoline （SaBOX） ligand, the [4＋2] annulations proceeded smoothly with a broad substrate scope. 22 examples were studied, leading to the corresponding products with various functional groups in 41%-99% yields with 〉99/1 dr and 90%-96% ee. The resulting product with two ester groups was mono-reduced, giving the corresponding product in excellent diastereoselectivity without loss of the enantiopurity.

Copper(I)/Sa BOX catalyzed highly diastereo- and enantio-selective cyclopropanation of cis-1,2-disubstituted olefins with a-nitrodiazoacetates

A copper-catalyzed highly stereoselective cyclopropanation of 1,2-disubstituted olefins with α-nitrodiazo acetates has been developed, giving the desired products in up to 97 % yields, up to 〉99/1 dr and up to 98 % ee, which provides an efficient access to the synthesis of optical active cyclopropane α-amino acids and unnatural α-amino acid derivatives.

Chromium-catalyzed asymmetric synthesis of 1,3-diols

An efficient,chromium-catalyzed highly enantioselective preparation of protected 1,3-diols has been achieved.In the presence of a chiral chromium catalyst using the carbazole-based bisoxazoline as the chiral ligand,a variety of optically pure 1,3-diols were synthesized in 34%-87%yields with up to 98%ee.The benzyl as well as silyl ethers were suitable substitutions for the hydroxyl group.Meanwhile,aromatic,aliphatic and α,β-unsaturated aldehydes are well tolerated under the mild reaction conditions.

Highly enantioselective cyclopropanation of trisubstituted olefins

A highly efficient asymmetric cyclopropanation of trisubstituted olefins with methyl diazoacetate has been developed in terms of an elaborate modified chiral bisoxazoline/copper complex as a catalyst. A broad scope of substrates is compatible with this catalyst system, including various trisubstituted olefins bearing different aryl-, fused aryl-and alkyl-substituents, providing an easy access to optically active 1,1-dimethyl cyclopropanes in good yields with excellent diastereo-and enantio-selectivity.