Copper-Catalyzed Asymmetric Addition Research Articles

Copper-catalyzed asymmetric addition of diethylzinc to Boc-protected imines

A new class of substrates has been tested in the addition of Et 2Zn, catalyzed by copper and phosphoramidite, providing the expected α branched protected amine in quantitative conversion, good yield and excellent enantioselectivity up to 97%.

Catalytic Asymmetric Synthesis of α,α,α-Trifluoromethylamines by the Copper-Catalyzed Nucleophilic Addition of Diorganozinc Reagents to Imines

[reaction: see text] A copper-catalyzed asymmetric addition of diorganozinc reagents to N-phosphinoylimines has been developed for the synthesis of chiral alpha,alpha,alpha-trifluoromethylamines. The trifluoromethyl ketimines, generated in situ from the corresponding hemiaminals, led to the chiral amides in high yields (71-89%) and excellent enantiocontrol (91-99% ee).

Chiral N-heterocyclic carbene ligands based on a biisoquinoline template

New chiral imidazolinium salts with tunable steric features, based on a biisoquinoline template, have been developed and structurally characterised using single crystal X-ray crystallography. The trans PdI(2)(NHC)(2) complex was prepared by reaction of the parent H(4) imidazolinium salt with Pd(OAc)(2) in the presence of NaI, and the solid state structure determined by X-ray crystallography. The rigid, chiral, biisoquinoline geometry of the H(4) imidazolinium salt was found to be maintained upon ligand complexation. The sterically unencumbered parent biisoquinoline ligand has been found to give high conversion with modest enantioselectivity in the copper-catalysed asymmetric addition of diethylzinc to cyclohexenone.

A New Class of Substituted Aryl Bis(oxazoline) Ligands for Highly Enantioselective Copper-Catalyzed Asymmetric Aldol Addition of Dienolsilane to Pyruvate and Glyoxylate Esters

[reaction: see text] A new class of bis(oxazoline) ligands are introduced that feature o-alkoxyaryl substituents and provide the highest enantioselectivities yet reported for the copper-catalyzed asymmetric dienosilane aldol addition to pyruvate and glyoxylate esters. Enantioselectivities up to 98% ee (before recrystallization) and isolated yields up to 91% were observed. Additionally, chloride counterions were found to be superior to triflate for this reaction.

Mixed thioether-phosphite and phosphine-phosphite ligands for copper-catalyzed asymmetric 1,4-addition of organometallic reagents to cyclohexenone

A series of thioether-phosphite and phosphine-phosphite ligands have been tested in the copper-catalyzed asymmetric addition of organometallic reagents to 2-cyclohexenone. In all the cases, excellent reaction rates (TOF>1200 h −1) and chemoselectivities for the 1,4-product have been obtained, while enantioselectivities have been moderate.

Efficient Chiral Amidophosphine Ligand for Copper-catalyzed Asymmetric Addition of Diethylzinc to N-Sulfonylimines

Abstract Structure study of a chiral amidophosphine ligand for copper-catalyzed asymmetric addition reaction of diethylzinc with the N-tosylimine reached to the new chiral phosphine bearing the bulky substituent on the pyrrolidine ring, which significantly improved catalytic performance to give the adduct in 96% yield and 93% ee after 3 h.

Copper-catalysed asymmetric 1,4-addition of organometallic reagents to 2-cyclohexenone using novel phosphine-phosphite ligands

A series of novel non-symmetrical phosphine-phosphite ligands 1– 10 have been tested in the copper-catalysed asymmetric addition of diethylzinc and triethylaluminium to 2-cyclohexenone. In all cases, excellent conversion and regioselectivities for the 1,4-product were found. Good enantiomeric excesses (up to 62%) were obtained when triethylaluminium was used as the alkylating reagent.