Huilin Chen

Highly enantioselective resolution of terminal epoxides using polymeric catalysts

Poly-salen-Co(III) complexes were employed in the hydrolytic kinetic resolution (HKR) of terminal epoxides and ees up to 98% were obtained. In the HKR of epichlorohydrin, the polymeric catalysts can be recovered and modified for recycling. The recovered polymer catalyst shows good activity and selectivity.

Asymmetric Cyclopropanation of Styrene Catalyzed by Cu–(Chiral Schiff-Base) Complexes

Asymmetric cyclopropanation of olefins was carried out with chiral copper-Schiff base complexes derived from copper acetate monohydrate, substituted salicylaldehydes and a chiral amino alcohol. Substituents on salicylaldehyde framework demonstrate a significant effect on the steroselectivities. Those with electron-withdrawing properties enhance the selectivities, whereas bulky sustituents in ortho position to the phenol hydroxy group decrease the selectivities. An ee of more than 98% was achieved for the reaction of styrene with diazoacetate

Ferrocenylphosphine-imine ligands for Pd-catalyzed asymmetric allylic alkylation

Ferrocenylphosphine-imine ligands 6 derived front (r,s)-ppfnh2-r 5 and a variety of benzaldehydes were applied in the pd-catalyzed asymmetric allylic alkylation of 1,3-diphenylprop-2-en-1-yl acetate 7a or pivalate 7b with dimethyl malonate. the substituent effects on the catalytic reaction were investigated, and 96% e.e. with 99% yield was achieved when the m-nitro substituted ligand 6k was used. (c) 2002 elsevier science ltd. all rights reserved.

New efficient P,N,O-tridentate ligands for Ru-catalyzed asymmetric transfer hydrogenation

Abstract New chiral P,N,O Schiff base ligands derived from substituted salicylaldehyde and ( R )-1-[( S )-2-(diphenylphosphino)-ferrocenyl]ethylamine[( R , S Fc )-PPFNH 2 ] have been prepared and employed in ruthenium catalyzed asymmetric transfer hydrogenation of simple ketones. Up to 94% e.e. with 99% conversion was obtained when the electron-withdrawing 3,5-dinitro substituted ligand 2f was used.

Structural probing of d-fructose derived ligands for asymmetric addition of diethylzinc to aldehydes

Abstract A series of new chiral ligands derived from d -fructose have been synthesized and applied in the enantioselective addition of diethylzinc to aldehydes. Comparison of the enantioselectivities obtained with these ligands demonstrated that the catalytic properties are highly dependent upon the structure of ligands, a rational explanation of the structural effects on the catalytic properties is provided.

Highly enantioselective resolution of terminal epoxides with cross-linked polymeric salen-Co(III) complexes

Abstract Crosslinked polymeric salen–Co(III) complexes derived from a novel dialdehyde and a trialdehyde were synthesized and employed in the hydrolytic kinetic resolution (HKR) of terminal epoxides. Up to 99% ee were obtained with only 0.16–0.02 mol% of catalyst (based on catalytic unit).

Substituted salen-Ru(II) complexes as catalysts in the asymmetric cyclopropanation of styrene by ethyl diazoacetate: the influence of substituents and achiral additives on activity and enantioselectivity

A series of alkyl-, halogen- and nitro-substituted salen ligands, 1, have been employed in the asymmetric cyclopropanation of styrene with ethyl diazoacetate by its ruthenium(II) complex with [RuCl2(p-cymene)](2) or RuCl2(PPh3)(3) as precursors. The introduction of appropriate electron withdrawing groups in the salen ligands benefited the enantioselectivity of the reaction. Some additives, including O-donor, N-donor and P-donor ligands, were added to the reaction to improve the enantioselectivity and activity, and e.e.s of up to 80% were achieved. In the salen/[RuCl2(p-cymene)](2) system, the (1R,2S)-isomer was obtained in 80.2% e.e. by using the salen ligand If derived from 3,5-dibrominated salicylaldehyde with Et3N as additive. E.e.s of up to 81.3% for (1S,2R)-isomers were achieved by using the complex 2 synthesized from the nitro-substituted ligand Im and RuCl2(PPh3)(3). A possible mechanism was also discussed

Highly efficient and enantioselective cyclopropanation of styrene with diazoacetates using a new copper-(Schiff-base) catalyst

Abstract A new copper-(Schiff-base) complex, derived from ( S )-2-amino-1,1-di(3,5-di- t -butylphenyl)propanol, 2-hydroxy-5-nitrobenzaldehyde and copper acetate monohydrate, was used as an efficient catalyst for the cyclopropanation of styrene with diazoacetates, affording ees of up to 98%.

Synthesis of novel ferrocenylphosphine-amidine ligands with central and planar chirality and their diastereomeric effect in Pd-catalyzed asymmetric allylic alkylation

Abstract Some novel ferrocenylphosphine-amidine ligands with central and planar chirality were prepared from ( R , S p )-PPFNH 2 -R 3 and its diastereomer ( S , S p )-PPFNH 2 3a . The efficiency and diastereomeric impact of these ferrocenylphosphine-amidine ligands in the palladium-catalyzed asymmetric allylic substitution was examined, and up to 96% e.e. with 98% yield was achieved by the use of ligand ( R , S p )- 4a with a methyl group in the amidino moiety. The results also indicated that ( R )-central chirality and ( S p )-planar chirality in these ferrocenylphosphine-amidine ligands were matched for the palladium-catalyzed asymmetric allylic alkylation.

Synthesis of novel ferrocenylphosphine-amidine ligands and their application in Pd-catalyzed asymmetric allylic alkylation

A family of novel ferrocenylphosphine-amidine ligands derived from (R)-(S)-PPFNH2-R 5 was applied to the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenylprop-2-en-1-yl acetate 8a or pivalate 8b with dimethyl malonate. Up to 94% e.e. was achieved when ligand 6b was used