Weiliang Chen

Catalytic asymmetric chloroamination reaction of α,β-unsaturated γ-keto esters and chalcones.

Highly efficient catalytic chloroamination reaction of α,β-unsaturated γ-keto esters and chalcones has been developed via a chloronium-based mechanism to deliver anti-regioselective vicinal chloroamines instead of the aziridinium intermediates delivered aminochlorides. The combination of TsNCl(2) and TsNH(2) as reagents made the transformation highly efficient, delivering the γ-carbonyl-β-chloro-α-amino acid derivatives and α-chloro-β-amino-ketone derivatives in nearly quantitative yields with up to 99% ee and 99:1 dr under 0.05-0.5 mol % catalyst loading. TsNHCl was demonstrated to act as the key reactive species to form a bridged chloronium ion intermediate in the presence of a chiral scandium complex. The method might provide useful information for further realization of other haloamination reactions.

Catalytic Asymmetric Synthesis of Quaternary α-Hydroxy Trifluoromethyl Phosphonate via Chiral Aluminum(III) Catalyzed Hydrophosphonylation of Trifluoromethyl Ketones

The chiral hydrogenated tridentate Schiff base-aluminum(III) complex has been first applied in the catalytic enantioselective hydrophosphonylation of trifluoromethyl ketones. The side reactions related to phospha-Brook rearrangement were completely avoided, and the corresponding quaternary α-hydroxy trifluoromethyl phosphonates have been first synthesized in good yields with high enantioselectivities (up to 90% ee).