Asymmetric addition of dimethylzinc to alpha-ketoesters catalyzed by (-)-MITH

This investigation describes the catalytic asymmetric addition of dimethylzinc to alpha-ketoesters in the presence of (-)-MITH ( 5) and triethyl borate as an additive to give the corresponding chiral alpha-hydroxy esters with good yields and high enantioselectivities.     

The first catalytic asymmetric addition of dialkylzincs to alpha-ketoesters

[formula: see text] The first catalytic, enantioselective addition of organoznic reagents to alpha-ketoesters is described. Modular bifunctional salen catalysts that contain Lewis acid and Lewis base activating groups accelerate the carbonyl addition to a much greater extent than the competing carbonyl reduction. alpha-Hydroxyesters containing new quaternary stereogenic centers are obtained in high yield and moderate enantiomeric excess. Enrichment to 98% ee can be effected by recrystallization of the corresponding alpha-hydroxy acid.     

Catalytic enantioselective aryl transfer: asymmetric addition of boronic acids to aldehydes using pyrrolidinylmethanols as ligands

Pyrrolidinylmethanols, easily accessible from readily available (S)-proline, were applied in zinc-catalyzed addition of arylboronic acids to aromatic aldehydes; the reaction was found to proceed in excellent yields and high enantioselectivities (up to 98% ee).     

Catalytic asymmetric diethylzinc addition to diphenylphosphionyl imines using chiral tert-butanesulfinylphosphine ligands

A class of novel chiral tert-butanesulfinylphosphine ligands were designed and synthesized by a concise two-step route with high yields. High activities and enantioselectivities (up to 94% ee) were achieved when using them in catalytic asymmetric diethylzinc addition to diphenylphosphionyl imines.     

Effect of microwave heating in the asymmetric addition of dimethylzinc to aldehydes

Microwave-heated enantioselective additions of dimethylzinc to various aldehydes are reported. Dramatically reduced reaction times and lower catalyst loadings (5%), compared with conventionally used conditions, can be achieved, with excellent yields and just small loss of enantioselectivity (up to 83% enantioselectivity is achieved). In the reaction with aliphatic aldehydes the same enantioselectivity has been achieved for microwave-heated and conventional room temperature conditions.     

Catalytic asymmetric transfer hydrogenation of alpha-ketoesters with hantzsch esters

C2-symmetric chiral copper(II)-bisoxazolines function as alcohol dehydrogenase mimics and catalyze highly enantioselective transfer hydrogenations of alpha-ketoesters with Hantzsch esters as a synthetic NADH analogue to give alpha-hydroxy esters in excellent enantioselectivities. [reaction: see text].     

Rhodium-catalyzed asymmetric conjugate addition of arylboronic acids to nitroalkenes using olefin-sulfoxide ligands

An efficient rhodium/olefin-sulfoxide catalyzed asymmetric conjugate addition of organoboronic acids to a variety of nitroalkenes has been developed, where 2-methoxy-1-naphthyl sulfinyl functionalized olefin ligands have shown to be highly effective and are applicable to a broad scope of aryl, alkyl, and heteroaryl nitroalkenes.     

Synthesis of a fluorous ligand and its application for asymmetric addition of dimethylzinc to aldehydes

A new fluorous ligand was synthesized from the acetonide of dimethyl tartarate, which showed excellent asymmetric induction on the addition of dimethylzinc to aldehydes. This ligand will be useful for synthesis of bioactive compounds with a methyl carbinol moiety. It could be recycled without using a fluorous solvent or a fluorous column.     

Catalytic enantioselective addition of diethylzinc to aldehydes using aziridine based chiral ligands

The readily available ferrocenyl substituted aziridinylmethanol 1 (FAM-1) was used as a chiral catalyst in the diethylzinc addition reaction to aromatic and aliphatic aldehydes to give secondary alcohols in high yields and up to 99% enantiomeric excess at room temperature. The catalyst can be recovered and used without losing its activity.     

Catalytic enantioselective addition of organometallic reagents to N-formylimines using monodentate phosphoramidite ligands

The asymmetric synthesis of protected amines via the copper/phosphoramidite-catalyzed addition of organozinc and organoaluminum reagents to N-acylimines, generated in situ from aromatic and aliphatic alpha-amidosulfones, is reported. High yields of optically active N-formyl-protected amines and enantioselectivities up to 99% were obtained. Under the reaction conditions, partial oxidation of the phosphoramidite ligand to the corresponding phosphoric amide was detected. A preliminary study on the origin and the effect on the catalytic addition reaction is presented.     

Catalytic asymmetric conjugate addition of nitroalkanes to cycloalkenones

Nitroalkanes add to cyclic and acyclic enones in an enantioselective manner in the presence of catalytic quantities of L-proline and trans-2,5-dimethylpiperazine as excess additive.     

Catalytic asymmetric addition of dialkylzinc reagents to alpha-aldiminoesters

[reaction: see text] The first catalytic, enantioselective addition of organozinc reagents to alpha-aldiminoesters is described. The use of a Lewis acid/Lewis base containing bifunctional catalyst preorganizes both reactive substrates to promote enantioselective addition over the racemic background reaction and alternative addition modes. Alcohol additives were found to enhance the enantioselection. The addition product was also found to cyclize with remaining substrate to provide imidazolidines.     

Efficient asymmetric addition of diethylzinc to aldehydes using 3‐hydroxyazetidine derivatives as chiral ligands

A new series of chiral 3‐hydroxyazetidines has been prepared from (S)‐1‐(4‐methoxyphenyl)ethylamine. These ligands have shown excellent catalytic activities and enantiomeric selectivities in asymmetric addition of diethylzinc to aromatic aldehydes. Copyright © 2008 John Wiley & Sons, Ltd.     

Catalytic asymmetric conjugate addition of grignard reagents to alpha,beta-unsaturated sulfones

A highly efficient method is reported for the asymmetric conjugate addition of Grignard reagents to alpha,beta-unsaturated 2-pyridylsulfones. Using a Cu/TolBinap complex, excellent enantioselectivities and high yields are obtained for a wide variety of aliphatic substrates.     

New bis-steroidal axially chiral diols as ligands for the asymmetric addition of diethylzinc to aldehydes

New axially chiral steroidal binaphthols, prepared from estrone, were applied in the form of their Ti-alkoxides as catalysts for the addition of diethylzinc to aldehydes. The addition reactions proceeded with high yields and enantioselectivities up to 86%.     

Radical addition of ethers to imines initiated by dimethylzinc

Ethers undergo addition to imines in the presence of dimethylzinc and air through a radical process. [reaction: see text]     

Catalytic asymmetric Michael addition with curcumin derivative

Catalytic asymmetric Michael additions with curcumin derivatives were achieved by a new series of tertiary amine-thiourea organocatalysts to afford the Michael adducts in high yields and excellent enantioselectivities.     

Aminosubstituted tert-butylsulfinylferrocenes as a new family of chiral ligands: asymmetric addition of diethylzinc to aldehydes

A ready access to a new family of planar chiral ferrocenes, the (RFc,RS)-2-amino substituted 1-tert-butylsulfinylferrocenes, is described; in the case of the sulfonamide series enantioselectivities of up to 96% were obtained in the addition of Et2Zn to aromatic aldehydes.