Aerobic copper-catalyzed synthesis of (E)-alkenyl sulfones and (E)-β-halo-alkenyl sulfones via addition of sodium sulfinates to alkynes

Copper-catalyzed sulfonylation of alkynes using sodium sulfinates in air produced regio- and stereoselectively (E)-alkenyl sulfones. When a CuCl catalyst was employed, the hydrosulfonylation proceeded syn-selectively, and (E)-alkenyl sulfones were synthesized in excellent yields. In contrast, the reaction using CuI catalyst produced (E)-β-haloalkenyl sulfones anti-selectively in the presence of potassium halides. Furthermore, the (E)-β-bromoalkenyl sulfones are possible to convert into various alkenyl sulfones by Suzuki–Miyaura coupling.     

N-Heterocyclic carbene–gold(I)-catalyzed carboheterofunctionalization of alkenes with arylboronic acids

A new approach to the synthesis of pyrrolidine, tetrahydrofuran, and imidazolidin-2-one via N-heterocyclic carbene–gold(I)-catalyzed intramolecular amino- or oxyarylation reactions from a wide variety of alkene substrates such as N-allyl amides, alcohols, carboxylic acids, and ureas in the presence of Selectfluor under mild conditions has been developed.     

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.     

Synthesis and chemical properties of cyclic β-keto sulfones (review)

Published data on the synthesis and chemical properties of dihydrothiophen-3(2H)-one 1,1-dioxide, dihydro-2H-thiopyran-3(4H)-one 1,1-dioxide, 1-benzothiophen-3(2H)-one 1,1-dioxide, and 1H-isothio-chromen-4(3H)-one 2,2-dioxide are reviewed. The choice of subjects was based on the presence of identical structural fragments, carbonyl, active methylene, and sulfonyl groups.     

Cu(I)- and Cu(II)-catalyzed cyclo- and Michael addition reactions of unsaturated β-ketoesters

The α-alkylidene β-ketoesters 2-carbethoxycyclopentenone (1a) and ethyl 2-benzoylacrylate (1b) react with 1,2-dimethylbutadiene (2) (Diels-Alder), N-benzyl-N-(cyclohexylethynyl)-4-methylbenzenesulfonamide (3) (Ficini reaction), ethynyl(phenyl)sulfane (4) ([2 + 2] cycloaddition), and 1,2,5-trimethyl-1H-pyrrole (5) (Michael addition) in the presence of copper(I) (6) or copper(II) triflate (7) (1-2 mol %) in dichloromethane. This convenient protocol converts 1a and 1b to the corresponding cycloaddition (8-10) or Michael addition (11) products in good yields after reaction times of 0.5-3 h without requiring purified solvents or inert gas atmosphere.     

Ru/Me-BIPAM-catalyzed asymmetric addition of arylboronic acids to aliphatic aldehydes and α-ketoesters

A ruthenium-catalyzed asymmetric arylation of aliphatic aldehydes and α-ketoesters with arylboronic acids has been developed, giving chiral alkyl(aryl)methanols and α-hydroxy esters in good yields. The use of a chiral bidentate phosphoramidite ligand (Me-BIPAM) achieved excellent enantioselectivities.     

Pd-catalyzed asymmetric conjugate addition of arylboronic acids to 2-nitroacrylates: a facile route to β-homophenylglycines

Asymmetric conjugate addition of arylboronic acids to 2-nitroacrylamide in the presence of cationic palladium–Chiraphos complex proceeds with high yield and enantioselectivity (73–89% ee) using as low as 0.05–0.25 mol % of the catalyst. The adducts can be smoothly transformed into the corresponding β²-homophenylglycines in two simple steps.     

Novel efficient synthesis of β-fluoro-β-(trifluoromethyl)styrenes

CF₃CFBr₂ was employed in catalytic olefination reactions of aromatic aldehydes. In situ prepared hydrazones of aldehydes were transformed to β-fluoro-β-(trifluoromethyl)styrenes by reaction with CF₃CFBr₂ under CuCl catalysis. Based on this reaction, a novel stereoselective approach towards β-fluoro-β-(trifluoromethyl)styrenes was elaborated. Nucleophilic vinylic substitution of fluorine by secondary amines, thiolates and alkoxides in β-fluoro-β-(trifluoromethyl)styrenes was also tested.     

K2S2O8-mediated decarboxylative oxysulfonylation of cinnamic acids: A transition-metal-free synthesis of β-keto sulfones

A new paradigm of the oxidative decarboxylative sulfono functionalization of cinnamic acids with sulfinate salts mediated by K₂S₂O₈ under aerobic conditions to afford synthetically and biologically relevant β-keto sulfones has been described. It is the first report on the transition-metal-free synthesis of β-keto sulfones from cinnamic acids, which employs environmentally benign, readily available and inexpensive starting materials and oxidants, viz. air and K₂S₂O₈.     

Rhenium-catalyzed regio- and stereoselective addition of two carbon units to terminal alkynes via carbon-carbon bond cleavage of β-keto sulfones

Treatment of β-keto sulfones with terminal alkynes gave unsaturated δ-keto sulfones in good to excellent yields under rhenium catalysis. In this reaction, the insertion of the alkynes into the nonstrained carbon-carbon single bond between the α- and β-positions of the β-keto sulfones proceeded smoothly, and (Z)-isomers were produced with high regio- and stereoselectivities.     

Enantioselective hydrogenation of β-keto sulfones with chiral Ru(II)-catalysts: synthesis of enantiomerically pure butenolides and γ-butyrolactones

A series of β-hydroxy sulfones were synthesized with high enantioselectivities via a new enantioselective ruthenium-catalyzed hydrogenation using MeO-BIPHEP as a ligand. Some β-hydroxy sulfones were used in the synthesis of optically active butenolides and γ-butyrolactones with high yields and enantioselectivities over 95%.     

Rh(I)-catalyzed asymmetric 1,2-additions of arylboronic acids to isatins with chiral sulfur–alkene hybrid ligands

A rhodium-catalyzed asymmetric 1,2-addition of arylboronic acids to isatins with chiral sulfur–alkene hybrid ligands was achieved, and a variety of 3-aryl-3-hydroxy-2-oxindoles were obtained in moderate to good yields with up to 85% ee and a biologically active compound was synthesized with this strategy.     

Practical and stereoselective synthesis of β-amino sulfones from alkyl phenyl sulfones and N-(tert-butylsulfinyl) aldimines

A practical and straightforward approach for the highly stereoselective synthesis of β-amino sulfones was developed. With lithium bis(trimethylsilyl)amide as the base, the corresponding sulfone-stabilized carbanion derived from alkylphenyl sulfone can be transferred to N-(tert-butylsulfinyl) aldimines in excellent yields and with high diastereoselectivity.     

Rh(Ⅲ)-catalyzed C8 arylation of quinoline N-oxides with arylboronic acids

Herein,we report the first Rh~Ⅲ-catalyzed regioselective C8 arylation of quinoline N-oxides with commercially available arylboronic acids as coupling partners.This procedure is simple,and the reaction shows perfect regioselectivity,a broad substrate scope,and isolated yields of up to 92%.We demonstrate the utility of the reaction by using it for late-stage functionalization of a fungicide.     

Fluorinated anilides of β-keto acids and their Cu(II) complexes

Pentafluoroanilides of acetoacetic and benzoylacetic acids and their α-SCF₃ substituted analogues have been synthesized from the respective β-keto esters. Cu(II) complexes of the compounds obtained as well as of anilide of α-(trifluoromethylthio)acetoacetic acid have been prepared and characterized. The structure of these compounds has been elucidated on the basis of the elemental analysis and IR, MS, ¹H and ¹⁹F NMR spectra.     

Catalyzation of 1,4-additions of arylboronic acids to α,β-unsaturated substrates using nickel(I) complexes

Nickel(I) complexes were generated in situ from Ni (PPh₃)₂Cl₂ using activated iron and the complexes combined with N,N′-bis(4-fluorobenzylidene) ethane-1,2-diamine (BFBED) were then used as a catalyst for the 1,4-addition reaction of arylboronic acids to α,β-unsaturated substrates. The reaction proceeded to completion and did not require the addition of a base but the addition of potassium iodide is crucial to this cross-coupling reaction. Moreover, experimental observations suggested a possible Ni(I)–Ni(III) catalytic cycle mechanism.     

Ligand-free copper(Ι)-catalyzed Sonogashira-type coupling of arylboronic acids with terminal alkynes

An efficient ligand-free CuI-catalyzed Sonogashira-type coupling reaction of arylboronic acids with terminal alkynes under air is described. The electron-deficient alkynes gave the desired cross-coupling products in good yields. Thus, it represents a simple and alternative method for the traditional Sonogashira reaction.     

Rhodium/diene-catalyzed asymmetric arylation of N-Boc-protected α,β-unsaturated δ-lactam with arylboronic acids: enantioselective synthesis of 4-aryl-2-piperidinones

Utilizing toluene/isopropanol (20:1 to 40:1) as a solvent and KHF₂ as an additive, the rhodium/diene-catalyzed asymmetric arylation (RCAA) reaction of arylboronic acids to N-Boc-protected α,β-unsaturated δ-lactam proceeded smoothly to afford chiral 4-aryl-2-piperidinones with high to excellent yields (up to 94%) and enantioselectivities (up to >99% ee). Further conversion of adduct (R)-1-(tert-butyloxycarbonyl)-4-(4-chlorophenyl)-2-piperidone to (R)-Homobaclofen hydrochloride was also presented.     

Rhodium-catalyzed asymmetric addition of arylboronic acids to γ-phthalimido-substituted-α,β-unsaturated carboxylic acid esters: an approach to γ-amino acids

Efficient Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to ethyl-γ-phthalimidocrotonate by using bis-sulfoxide ligand affords γ-aminobutyric acid (GABA) derivatives with high enantioselectivities (90-96% ee) under mild conditions. Optically pure (S)-Baclofen and (S)-Rolipram have been prepared successfully through this synthetic route.