Catalytic enantioselective fluorination of oxindoles

We have developed a highly efficient catalytic enantioselective fluorination of oxindole derivatives. In the presence of a catalytic amount of chiral Pd complex 2 (2.5 mol %), various substrates, including aryl- and alkyl-substituted oxindoles, were fluorinated in a highly enantioselective manner (up to 96% ee). In addition, when R was a hydrogen atom, enantioselective fluorination followed by solvolysis gave a monofluorinated ester with up to 93% ee. To our knowledge, this is the first example of catalytic enantioselective fluorination of oxindoles.     

A formal enantioselective acetate Mannich reaction: the nitro functional group as a traceless agent for activation and enantiocontrol in the synthesis of beta-amino acids

A two-step procedure involving the enantioselective addition of alpha-nitro esters to imines, followed by reductive denitration, provides a convenient new enantioselective synthesis of beta-amino acids. Specifically, beta-phenyl alanine derivatives with up to 98% ee are formed in good yield (64-88%) over two steps. The utility of the approach is demonstrated through the first enantioselective synthesis of the key beta-amino acid of (+)-chaenorhine.     

Catalytic enantioselective conjugate addition of aromatic amines to fumarate derivatives: asymmetric synthesis of aspartic acid derivatives

The catalytic enantioselective conjugate addition of aromatic amines to fumarate derivatives promoted by chiral palladium complexes is described. Treatment of aniline derivatives with fumaryl pyrrolidinone as Michael acceptor under mild reaction conditions afforded the corresponding chiral aspartic acid derivatives with excellent enantiomeric excesses (83–96% ee).     

Catalytic asymmetric synthesis of stable oxetenes via Lewis acid-promoted [2+2] cycloaddition

A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP-Pd catalyst has been established. This is the first enantioselective synthesis of stable oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF(3)-substituted compounds with high stereoselectivity.     

Phosphahelicenes in Asymmetric Organocatalysis: [3+2] Cyclizations of γ‐Substituted Allenes and Electron‐Poor Olefins

The first use of phosphahelicene in enantioselective organocatalysis is reported. New chiral phosphahelicenes have been prepared and enable highly enantioselective [3+2] cyclization reactions between arylidene‐ or alkylidenemalononitriles and γ‐substituted allenoates or cyanoallenes. These reactions afford cyclopentene derivatives in both high yields and diastereoselectivities, with enantiomeric excesses of up to 97 %.     

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.     

Direct one-pot highly enantioselective assembly of polyketide and carbohydrate synthons

A short, direct, catalytic, enantioselective synthesis of polyketide segments and carbohydrates is presented. The novel, direct, one-pot, organocatalytic asymmetric tandem cross-aldol/Horner-Wittig-Emmons reactions assemble polyketide and carbohydrate derivatives in good yield with 93-98% ee. The one-pot catalytic asymmetric tandem reaction was applied to a highly enantioselective formal de novo synthesis of the rare carbohydrate, l-altrose.     

A catalytic asymmetric method for the synthesis of gamma-unsaturated beta-amino acid derivatives

Catalytic enantioselective synthesis of beta-amino acid derivatives is an area of intense interest, due to the importance of these compounds as components in pharmaceutical agents and peptidomimetics. In this report, we present the first catalytic enantioselective method for the synthesis of gamma-unsaturated beta-amino acids and their corresponding 1,3-amino alcohol derivatives. This methodology takes advantage of a highly enantioselective vinylzinc addition to an aldehyde to set chirality. The resulting allylic alcohols are then transformed into the corresponding allylic amines via Overman's [3,3]-sigmatropic imidate rearrangement, and subsequent one-pot deprotection-oxidation of a pendant oxygen leads to the gamma-unsaturated beta-amino acid derivatives of high enantiopurity.     

Facile enantioseparation and recognition of mandelic acid and its derivatives in self‐assembly interaction with chiral ionic liquids

Mandelic acid and its derivatives are important medical intermediates in the pharmaceutical industry. Different stereoisomers exhibited distinct biological properties to human bodies. Given that, enantioselective recognition and separation of mandelic acid are of great importance. In this study, four novel different types of chiral ionic liquids bearing designed functional groups were synthesized and successful enantioselective precipitation with mandelic acid and its derivatives. That is, (R, R)‐chiral ionic liquid 1 can coprecipitated with S‐mandelic acid and its derivatives was observed. In addition, good correlation coefficient is achieved by using electrospray mass spectrum at negative ion pattern for quick analysis of the enantioselective precipitation, which could be served as a method of enantioselective recognition. The possible intermolecular interactions are established after systematical studies by NMR spectroscopy and DFT calculations.     

Highly enantioselective preparation of tricyclo[4.4.0.0]decene derivatives via catalytic asymmetric intramolecular cyclopropanation reactions of α-diazo-β-keto esters

The enantioselective preparation of the tricyclo[4.4.0.0^5,7]dec-2-ene derivatives via the catalytic asymmetric intramolecular cyclopropanation (CAIMCP) reactions of α-diazo-β-keto esters with excellent ee (95-98% ee) is described. The chiral building blocks reported herein would be versatile intermediates for enantioselective natural products synthesis.     

The synthesis of new optically active 2-methylquinoline derivatives and their application in the enantioselective addition of diethylzinc to aldehydes

Homochiral 2-methylquinoline derivatives have been synthesized and applied in the enantioselective addition of diethylzinc to aldehydes. Good yields and enantiomeric excesses of up to 91.4% were observed in these reactions.     

Asymmetric enamide hydrogenation using phosphinite thioglycosides: synthesis of D- and L-aminoesters using D-sugars as catalyst precursors

Diastereomerically pure cationic Rh(I) complexes derived from phosphinite thioglycosides I were used as catalysts in highly enantioselective hydrogenations of enamides. The conformational similarity of alpha-D-arabinopyranose with beta-L-galactopyranose allows the synthesis of both enantiomers of alpha-amino acid derivatives such as D- and L-DOPA in excellent ee (97% and 98%), using derivatives of the former sugar as catalyst precursors.     

One-pot enantioselective aziridination of olefins catalyzed by a copper(I) complex of a novel diimine ligand by using PhI(OAc)(2) and sulfonamide as nitrene precursors

A novel chiral C(2)-symmetric 1,4-diamine with multistereogenic centers at the backbone of the ligand has been synthesized from cheap natural product D-mannitol through multistep transformations. Its diimine derivative (3 a) was found to be highly effective for the enantioselective control of the copper-catalyzed asymmetric aziridination of olefin derivatives with PhI==NTs as the nitrene source, affording the corresponding N-sulfonylated azirindine derivatives in good to excellent yields with up to 99 % ee (ee=enantiomeric excess). The catalyst system discovered in the present work was also extended to a one-pot enantioselective aziridination by using sulfonamide/iodobenzene diacetate as the nitrene source. In this case, most reactions proceeded smoothly to give the corresponding products in moderate yields with good to excellent enantiomeric excesses (75-96 % ee).     

An achiral manganese salen catalyst encapsulated in a peptidic phosphonate homochiral solid for the enantioselective formation of diols by consecutive epoxidation and hydration reactions

An insoluble, porous, amorphous, homochiral material based on a polypeptide titanium-phosphonate scaffold with an encapsulated achiral Mn(III)-salen was prepared and characterized. Consecutive epoxidation and hydration of styrene and its derivatives by aqueous hypochlorite in THF showed the highly enantioselective (>99%) formation of styrene diol derivatives.     

Highly effective and enantioselective Phospho-Aldol reaction of diphenyl phosphite with N-alkylated isatins catalyzed by quinine

Cinchona alkaloids were first successfully reported to promote enantioselective Phospho-Aldol reaction of diphenyl phosphite to a variety of N-alkylated isatin derivatives in good to excellent yields (up to 99%) and moderate to good enantioselectivities (up to 73% ee) almost in no time.     

Organocatalyzed enantioselective synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylates

The organocatalyzed enantioselective synthesis of biologically active 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylate derivatives was achieved using bifunctional cinchona alkaloids as the catalysts. Using quinine thiourea as the catalyst, the tandem Michael addition-cyclization reaction between 1,3-cyclohexanediones and alkylidenecyanoacetate derivatives gives the desired products in high yields (up to 92%) and good ee values (up to 82%).     

Organocatalytic diastereo- and enantioselective Michael addition reactions of 5-aryl-1,3-dioxolan-4-ones

5-Aryl-1,3-dioxolan-4-one heterocycles derived from mandelic acid derivatives and hexafluoroacetone have been identified as new and effective pro-nucleophiles in highly diastereo- and enantioselective Michael addition reactions to nitro olefins catalyzed by bifunctional epi-9-amino-9-deoxy cinchona alkaloid derivatives. Diastereoselectivities up to 98% and enantioselectivities up to 89% for a range of nitro olefins and 5-aryl-1,3-dioxolan-4-ones under mild reaction conditions are reported.     

Enantioselective addition of diethylzinc to aldehydes in the presence of chiral aprotic ligands

Optically active amino thiocyanate derivatives of (−)-norephedrine were found to act as effective aprotic ligands for enantioselective addition of diethylzinc to aldehydes. This reaction provided optically active secondary alcohols with ee up to 96%.     

Enantioselective solution- and solid-phase synthesis of glutamic acid derivatives via Michael addition reactions

The enantioselective conjugate addition of Schiff base ester derivatives to Michael acceptors either in solution (56–89% e.e.) or on solid-phase (34–82% e.e.) gave optically active unnatural α-amino acid derivatives. The reaction was conducted in the presence of chiral, non-racemic quaternary salts derived from the cinchona alkaloids using neutral, non-ionic phosphazene bases.     

Asymmetric Synthesis of Potential Precursors of the HIV Drug MC1220 and Its Analogues by Hydrogenation of (1‐Arylvinyl)pyrimidines

Because MC1220 is a promising microbicide with anti‐HIV‐1 activity, the possibility for asymmetric synthesis of its potential precursors is explored. Here, we investigate asymmetric reduction of the vinyl double bond of 6‐(1‐arylvinyl)pyrimidine derivatives to their corresponding ethylidene analogues. Catalysts with ligands bearing trivalent phosphorus ligating the soft metals rhodium(I), ruthenium(II), or iridium(I) are used for asymmetric reduction of the vinyl derivatives 5a – e . The enantioselective reduction reaches 92% ee and about 71% conversion for reduction of the 6‐(1‐(3,5‐dimethylphenyl)vinyl)pyrimidine derivative 5b using the asymmetric catalyst catASium M(R)Rh ( 7m ). However, for the more sterically hindered double bond in the corresponding 2,6‐difluorophenyl derivative 5e , the enantioselective reduction dropped to 30% ee and 14% conversion.