Enantioselective α-hydroxylation of β-keto esters catalyzed by chiral S-timolol derivatives

A screen of aryloxy aminopropanol organocatalysts derived from the β-blocker inhibitor S-timolol determined the most active catalyst of asymmetric α-hydroxylation of β-keto esters. (R)-1-(tert-butylamino)-3-(3,4,5-trimethoxyphenoxy) propan-2-ol (3k) was the most effective derivative, enantioselectively catalyzing α-hydroxylation of β-keto esters using tert-butyl hydroperoxide as the oxidant in hexane to afford the corresponding products in excellent yield and with good enantioselectivity (up to 96% yield, 88% ee).     

Enantioselective α-hydrazination of α-fluoro-β-ketoesters catalyzed by chiral nickel complexes

The catalytic enantioselective electrophilic α-hydrazination promoted by chiral nickel complexes is described. Treatment of α-fluoro-β-ketoesters with azodicarboxylates as electrophilic amination reagents under mild reaction conditions afforded the corresponding α-amino α-fluoro-β-ketoesters with high yields (80-96%) and enantioselectivities (up to 78% ee).     

Enantioselective α-chlorination of β-keto esters and amides catalyzed by chiral imidodiphosphoric acids

Chiral imidodiphosphoric acids were employed as catalysts for the enantioselective α-chlorination of β-keto esters and amides using NCS as the chlorine source, providing a series of optically active products with good to high enantioselectivities (74–95% ee) and excellent yields (92–99%). This represents the first report of the Brønsted acid catalyzed enantioselective α-chlorination of cyclic β-keto derivatives.     

Enantioselective oxysulfenylation and oxyselenenylation of olefins catalyzed by chiral Brønsted acids

This paper describes Brønsted acid catalyzed enantioselective oxysulfenylation and oxyselenenylation of olefins. Enantiomerically enriched tetrahydrofurans are formed with up to 63% ee with dibenzoyl-d-tartaric acid and its derivatives as catalyst. Chiral β-carboxyl sulfides and selenides have also been obtained with up to 50% and 84% ee, respectively, via enantioselective desymmetrization of thiiranium and seleniranium ions in the presence of catalytic amounts of chiral binaphthol derived N-triflyl phosphoramide.     

Enantioselective α-chlorination of β-oxo esters catalyzed by chiral diterpenoid alkaloid derivatives

Easily accessible diterpenoid alkaloid derivatives have been used as organocatalysts in the enantioselective α-chlorination of β-oxo esters. The treatment of β-oxo esters with N-chlorophthalimide (NCP) as a chlorine source under mild reaction conditions afforded the corresponding α-chlorinated β-oxo esters in excellent yields (up to 98%) and with moderate enantioselectivities (up to 68% ee) in 30 min.     

Enantioselective synthesis of functionalized α-amino acids via a chiral guanidine catalyzed Michael addition reaction

Several chiral guanidines were evaluated as catalysts for the Michael reaction of glycine derivatives 7 with acrylic esters 8. The best result (30.4% ee) was obtained when 7b was reacted with 8b under the catalysis of guanidine 1 in THF.     

Enantioselective direct aza hetero-Diels-Alder reaction catalyzed by chiral Brønsted acids

[Structure: see text] The first chiral Br?nsted acid-catalyzed asymmetric direct aza hetero-Diels-Alder reaction has been described. The phosphoric acids, prepared from binol and H8-binol derivatives, have shown catalytic ability for the reaction of cyclohexenone with N-PMP-benzaldimine. A chiral phosphoric acid, derived from 3,3-di(4-chloropheneyl)-H8-binol, exhibited superior enantioselectivity, affording fairly good yields and enantioselectivities for the reaction of a range of aromatic aldimines with cyclohexenone.     

Enantioselective α-amination of branched aldehydes promoted by simple chiral primary amino acids

A series of simple chiral primary amino acids were first successfully applied to promote the enantioselective α-amination of branched aldehydes with azadicarboxylates and the desired adducts bearing quaternary stereogenic centers were obtained in excellent yields (up to 99%) and enantioselectivities (up to 97% ee).     

Enantioselective sulfenylation of α-nitroesters catalyzed by diarylprolinols

The organocatalytic sulfenylation of α-nitroesters mediated by diaryl-l-prolinols was developed. A range of α-sulfenylated α-nitroesters were obtained in good yields with moderate to good enantioselectivities.     

Enantioselective synthesis of α-amino acids in chiral reverse micelles

Through alkylation of ethyl 2-phthalimidoacetate in chiral reverse micelles formed from chiral surfactants, followed by hydrazinolysis and hydrolysis of the resulting products, optically active α-amino acids were synthesized. The highest enantioselectivity was 59.5%. Meanwhile, we have found that the asymmetric induction depends on the reaction temperature, the alkyl chain length of surfactant and the strucure of the surfactants.     

Enantioselective γ-addition reaction of rhodanines to allenoates catalyzed by chiral phosphine-carbamate

Phosphine-catalyzed enantioselective γ-additions of rhodanines to allenoates have been developed for the first time. With the employment of chiral cyclohexane-based phosphines, a wide range of substituted rhodanine derivatives containing tertiary chiral centers were constructed in good yields and high enantioselectivities.     

Enantioselective carbonyl-ene-type cyclization of α-ketoester and 2-substituted vinylsilane catalyzed by a chiral Cu-BOX complex

We developed an enantioselective carbonyl-ene-type cyclization using 2-substituted vinylsilane as a nucleophilic ene moiety catalyzed by a chiral copper-BOX complex. This reaction is the first example of enantioselective carbonyl-ene cyclization using a 1,2-disubstituted olefin. This methodology gave chiral indenols with a tetrasubstituted carbon.     

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.     

Enantioselective α-alkylation of unsaturated carboxylic acids using a chiral lithium amide

The regio- and stereochemistry of the alkylation of dienediolates from unsaturated carboxylic acids with benzylic halides, which often results in mixtures of isomers, can be controlled by means of changes in the lithium amide, allowing the α-regioisomer to be obtained as the major diastereoisomer. In addition, when chiral amines are used, moderate enantiomeric excesses can be attained.     

Asymmetric alkylation catalyzed by chiral alkali metal alkoxides of TADDOL. Synthesis of α-methyl amino acids

It is shown that sodium alkoxides formed from (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-bis(diphenylmethanol) ((R,R)-TADDOL) and some of its derivatives can be used as chiral catalysts for enantioselective alkylation of Schiff's bases derived from alanine with reactive alkyl halides. Acid hydrolysis of the reaction products affords (R)-α-methylphenyl-alanine, (R)-α-allylalanine, and (R)-α-methylnaphthylalanine in 61–93% yields and withee 69–94%. When (S,S)-TADDOL is used, the (S)-amino acid is formed. A mechanism explaning the observed features of the reaction is proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 926–932, May, 1999.     

Enantioselective intermolecular iodoacetalization of enol ethers catalyzed by chiral Co(III)-complex-templated Brønsted acids

The chiral Co(III)-complex-templated Brønsted acids were used as efficient bifunctional phase-transfer catalysts for the asymmetric intermolecular iodoacetalization of enol ethers, such as 3,4-dihydro-2H-pyran, 2,3-dihydrofuran, ethyl vinyl ether with alcohols and NIS, furnishing the 3-iodoacetals in high yield with up to 83:17 er.     

Rhodium catalyzed asymmetric 1,4-addition of arylboronic acids to β,γ-unsaturated α-keto ester using chiral tert-butanesulfinylphosphines ligands

Rh-Catalyzed asymmetric 1,4-selective addition of arylboronic acids to β,γ-unsaturated α-keto ester was developed using chiral tert-butanesulfinylphosphine as ligand, good yields (up to 87%), good 1,4-regioselectivities (up to 96:4), and high enantioselectivities (up to 94% ee) were achieved.     

Enantioselective aldol reactions of α,β-unsaturated ketones with trifluoroacetophenone catalyzed by a chiral primary amine

Chiral primary amine catalyzed direct asymmetric aldol reactions of ketones with trifluoroacetophenone, afforded trifluoromethylated β-hydroxycarbonyl aldol products bearing a quaternary carbon stereogenic center in high yields (up to 93% yield) and with high to excellent enantioselectivities of up to 99% ee.