Highly enantioselective 1,3-dipolar cycloaddition of imino esters with benzofuranone derivatives catalyzed by thiourea−quaternary ammonium salt

Highly enantioselective 1, 3-dipolar cycloaddition of 2-arylidene-benzofuran- 3(2H)-ones with imino esters catalyzed by thiourea?quaternary ammonium salts has been developed. This reaction provides efficient construction of a range of chiral spiro[benzofuran-2,3′-pyrrolidine] in high yields (up to 99%) and with good enantioselectivities (up to 99% ee) under mild conditions.     

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 conjugate addition of both aromatic ketones and acetone to nitroolefins catalyzed by chiral primary amines bearing multiple hydrogen-bonding donors

A new class of chiral primary amine catalysts bearing multiple hydrogen-bonding donors have been designed and synthesized. The newly developed bifunctional organocatalysts efficiently catalyzed not only enantioselective conjugate addition of aromatic ketones to nitroolefins in good yields (up to 87%) with excellent enantioselectivities (97→99% ee) but also enantioselective conjugate addition of acetone to nitroolefins in excellent yields (90-96%) with high enantioselectivities (up to 97% ee).     

Highly enantioselective Mannich reactions of imines with tert-butyl acetoacetate catalyzed by squaramide organocatalyst

Highly enantioselective Mannich reactions of imines bearing a benzothiazole moiety with tert-butyl acetoacetate, catalyzed by a cinchona-based squaramide organocatalyst have been developed. The corresponding benzothiazole β-keto ester derivatives were obtained in high yields (up to 99%) and with excellent enantioselectivities (up to 98% ee).     

Chiral phosphoric acid catalyzed aza-Friedel-Crafts alkylation of indoles with cyclic aryl α-ketimino esters

A highly enantioselective aza-Friedel-Crafts alkylation of indoles with cyclic aryl α-ketimino esters catalyzed by a chiral phosphoric acid has been developed, the corresponding α,α-disubstituted unnatural α-amino ester derivatives were obtained in moderate to high yields (67–85%) with high enantioselectivities (up to 93% ee) under mild reaction conditions.     

Chiral Brønsted acid-catalyzed regio- and enantioselective arylation of α,β-unsaturated trifluoromethyl ketones

The interesting examples of chiral phosphoric acid-catalyzed regio- and enantioselective arylation of α,β-unsaturated trifluoromethyl ketones were reported. The reaction proceeded well and the desired products were obtained in good yields (up to 99%) with moderate to good enantioselectivities (up to 88% ee). Several desired products were obtained with excellent optical purities after a single recrystallization. Subsequent reduction of enantiopure products with NaBH₄ afforded two diastereomers of chiral trifluoromethyl-substituted secondary alcohols with high enantioselectivities (98% ee).     

Catalytic enantioselective amination of silyl enol ethers using chiral dirhodium(II) carboxylates: asymmetric formal synthesis of (-)-metazocine

Dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate], Rh2(S-TFPTTL)4, is an exceptionally efficient catalyst for enantioselective aminations of silyl enol ethers derived from acyclic ketones or alpha,beta-enones with [N-(2-nitrophenylsulfonyl)imino]phenyliodinane (NsN=IPh), providing N-(2-nitrophenylsulfonyl)-alpha-amino ketones in high yields and with enantioselectivities of up to 95% ee. The effectiveness of the present catalytic protocol has been demonstrated by an asymmetric formal synthesis of (-)-metazocine.     

Bifunctional AgOAc/ThioClickFerrophos complex-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with aryl- and alkylidene malonates

AgOAc/ThioClickFerrophos complex-catalyzed 1,3-dipolar cycloaddition of glycine imino ester, the precursor of azomethine ylide, with aryl- and alkylidene malonates afforded the corresponding exo-cycloadducts, that is, proline ester derivatives in high yields with high enantiomeric excess (up to 99% ee). The reactions proceeded smoothly under base-free conditions demonstrating the bifunctional catalysis of the silver complex.     

First enantioselective organocatalytic allylation of simple aldimines with allyltrichlorosilane

A new organocatalytic system, novel chiral bisformamide and in situ generated L-proline-derived allylsilane reagent , which converts different aldimines to homoallylic amines in good to high yields (up to 95%) and good enantioselectivities (up to 85% ee) has been described.     

Enantioselective rhodium-catalyzed addition of arylboronic acids to trifluoromethyl ketones

The catalytic asymmetric 1,2-addition of a series of arylboronic acids to 2,2,2-trifluoroacetophenones is described with high isolated yields (up to 96%) and good enantioselectivities (up to 83% ee) using a rhodium(I)/phosphoramidite catalyst.     

Asymmetric addition of alkynes to imines in water catalyzed with a recyclable Cu(I)–bis(oxazoline) and stearic acid system

Stearic acid and its zinc salt were used as additives in the enantioselective alkyne addition to imines catalyzed by copper(I)–bis(oxazoline) (box) in water. The reactions took place smoothly with good yields and high enantioselectivities (up to 97% ee). Good enantioselectivities were maintained in a catalyst recycle study.     

l-Proline amides catalyze direct asymmetric aldol reactions of aldehydes with methylthioacetone and fluoroacetone

Direct aldol reactions of aldehydes with methylthio- and fluoroacetone catalyzed by proline amides have been investigated. l-Prolinamide 5e was found to be the best catalyst. Under the optimized reaction conditions, a series of aromatic and aliphatic aldehydes reacted smoothly with methylthioacetone, to generate 1-methylthio-4-hydroxyketones 3 in good yields and with high regio- and enantioselectivities. Excellent enantioselectivities of up to 98% ee were observed for aromatic aldehydes and even higher enantioselectivities of >99% ee were observed for aliphatic aldehydes. Asymmetric direct aldol reactions of fluoroacetone with aldehydes in the presence of 20 mol % of 5e preferentially occurred at the fluoromethyl group, yielding products with high enantioselectivities (up to 98% ee).     

Catalytic enantioselective allylation of aldehydes via a moisture-tolerant chiral BINOL-In(III) complex

A moisture-tolerant chiral indium complex has been developed to effect good enantioselectivities in the addition of allyltributylstannanes to aldehydes. The allylation of a variety of aromatic, α,β-unsaturated and aliphatic aldehydes resulted in both moderate to good yields and high enantioselectivities (up to 86% ee).     

Highly enantioselective allylation of aldehydes catalyzed by indium(III)-PYBOX complex

A chiral indium(III)-PYBOX complex prepared from indium triflate and chiral PYBOX has been discovered to effect high enantioselectivities in the addition of allyltributyl stannane to aldehydes. The allylation of a variety of aromatic, alpha,beta-unsaturated, and aliphatic aldehydes resulted in good yields and high enantioselectivities (up to 94% ee).     

Organocatalytic asymmetric cascade Michael/hemiketalization/retro-aldol reaction of 3-acetyl-oxindole with β,γ-unsaturated ketoesters catalyzed by bifunctional amino-squaramides

An unprecedented organocatalytic asymmetric Michael/Hemiketalization/retro-aldol cascade sequence catalyzed by bifunctional amino-squaramides is described. The corresponding adducts were generally obtained in high yields (up to 97%) with moderate diastereo- (up to 79:21 dr) and good enantioselectivities (up to 90% ee).     

Enantioselective Michael addition of anthrone to nitroalkenes catalyzed by bifunctional thiourea-tertiary amines

A highly bifunctional thiourea-tertiary amine-catalyzed enantioselective Michael addition reaction of anthrone to a wide variety of nitroalkenes has been developed, and the corresponding adducts were obtained smoothly in high yields (up to 97%) and good enantioselectivities (up to 94% ee).     

Catalytic enantioselective allylation of ketones via a chiral indium(III) complex

[reaction: see text] A chiral indium complex has been discovered to effect high enantioselectivities in the addition of allyltributylstannanes to ketones. The allylation of a variety of aromatic, alpha,beta-unsaturated and aliphatic ketones resulted in good yields and high enantioselectivities (up to 92% ee).     

Squaramide-catalyzed enantioselective Michael addition of malononitrile to chalcones

A highly enantioselective Michael addition of malononitrile to chalcones catalyzed by a chiral quinine-derived squaramide catalyst has been developed. This organocatalytic reaction at a very low catalyst loading (0.5 mol%) led to chiral γ-cyano carbonyl compounds in good yields with high enantioselectivities (up to 96% ee) under mild reaction conditions.     

One-pot asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones catalyzed by amino acid-derived sulfonamides

An organocatalyzed approach to the asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones using amino-acid derived sulfonamides as organocatalysts, which can be easily prepared starting from l-proline, l-alanine, and l-phenylalanine, has been developed in high yields (up to 92%) and with moderate to good enantioselectivities (up to 74% ee). Additionally, opposite enantioselectivities for primary and secondary amino acid sulfonamides have also been observed.     

Enantioselective synthesis of chiral sulfones by ir-catalyzed asymmetric hydrogenation: a facile approach to the preparation of chiral allylic and homoallylic compounds

A highly efficient and enantioselective Ir-catalyzed hydrogenation of unsaturated sulfones was developed. Chiral cyclic and acyclic sulfones were produced in excellent enantioselectivities (up to 98% ee). Coupled with the Ramberg-B?cklund rearrangement, this reaction offers a novel route to chiral allylic and homoallylic compounds in excellent enantioselectivities (up to 97% ee) and high yields (up to 94%).