Palladium-catalyzed asymmetric allylic C–H alkylation of 1,4-dienes and glycine Schiff bases

A highly regio-and enantioselective allylic C–H alkylation of 1,4-dienes with glycine Schiff bases has been established by chiral palladium-phosphoramidite catalysis. This reaction can proceed under mild conditions and tolerate a wide scope of 1,4-dienes,delivering structurally diverse chiral β-branched α-amino acid surrogates in moderate to high yields and with high levels of regio-, Z/E-, diastereo-and enantioselectivities.     

Palladium-catalyzed intramolecular allylic alkylation of α-sulfinyl carbanions: a new asymmetric route to enantiopure γ-lactams

Asymmetric intramolecular palladium-catalyzed allylic alkylation allowing access to disubstituted sulfinyl γ-lactams is described. The use of unsaturated amides bearing a sulfinyl group of defined absolute configuration together with enantiopure BINAP as the ligand in a biphasic medium provided good diastereoselectivities with clear solvent effect.     

Palladium-catalyzed asymmetric allylic alkylation of indoles by C–N bond axially chiral phosphine ligands

The palladium-catalyzed asymmetric allylic alkylation of indoles with 1,3-diphenyl-2-propenyl acetate using P/N-type ligands such as N-aryl indole, C–N bond axially chiral aminophosphine (aS)-L4, gave the desired products 1 in good yields and with moderate to high enantioselectivities (up to 90% ee).     

Ruthenium catalyzed asymmetric transfer hydrogenation of β-ketoesters

Chemoselective transfer hydrogenation of β-ketoesters to the corresponding alcohols is achieved in the presence of catalytic combinations of [RuCl₂(η⁶-arene)]₂ and ephedrine or diamino type chiral ligands with activities up to 190 h⁻¹ at 20°C and moderate to good enantiomeric excesses ranging from 36 to 94%.     

Palladium-catalyzed allylic alkylation using pyridino-oxazolines and quinolino-oxazolines as ligands—influence of steric factors

Four new chiral pyridino- and quinolino-oxazolines were subjected to the palladium-catalyzed alkylation of 1,3-diphenyl-2-propenyl acetate. The enantioselectivity varied (82–88% ee) with the steric properties of the ligands. The results are discussed in connection with results previously obtained using analogous ligands.     

Enantiomerically pure pyridine and 2,2′-bipyridine thioethers: new N–S chiral ligands for asymmetric catalysis. Palladium-catalyzed allylic alkylation

Diastereomeric pure pyridine and 2,2′-bipyridine thioethers, derived from (+)-camphor, were prepared and assessed in the enantioselective palladium-catalyzed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate. Enantioselectivities of up to 76% were obtained.     

Sulfur–imine mixed donor chelate ligands for asymmetric catalysis: enantioselective allylic alkylation

A new series of sulfur–imine mixed donor chiral ligands, prepared in only two steps from commercially available (S)-valinol, have been shown to give up to 94% enantiomeric excess in a palladium-catalysed allylic substitution reaction.     

Lewis base assisted Brønsted base catalysis: direct regioselective asymmetric vinylogous alkylation of allylic sulfones

A Lewis base assisted Brønsted base catalysis (LBABB) strategy is applied for direct asymmetric vinylogous alkylation of allylic sulfones with Morita–Baylis–Hillman (MBH) carbonates, in which a strong Brønsted base, tert‐butoxy anion, generated in situ from a tertiary amine catalyst and MBH carbonate, is crucial in activating unstabilized nucleophiles. The γ‐regioselective alkylation products were obtained with good to excellent enantiomeric excess values when catalyzed by a modified cinchona alkaloid.     

Palladium-catalyzed carbonylative/decarboxylative cross-coupling of α-bromo-ketones with allylic alcohols to γ,δ-unsaturated ketones

In this communication, a palladium-catalyzed carbonylative/decarboxylative cross-coupling of α-bromo-ketones with allylic alcohols has been developed. With Mo(CO)₆ as the CO source, γ,δ-unsaturated ketones were isolated in good yields. The release of CO₂ was confirmed as well.     

Synthesis of novel chiral phosphine-triazine ligand derived from α-phenylethylamine for Pd-catalyzed asymmetric allylic alkylation

A novel chiral phosphine-triazine ligand was synthesized from chiral model reaction of Pd-catalyzed allylic alkylation of rac-l,3-diphenylprop-2-en-l-yl pivalate with dimethyl malonate, good enantioselectivity (90% e.e.) was obtained by using this ligand.     

Modular chiral β-selenium-, sulfur-, and tellurium amides: synthesis and application in the palladium-catalyzed asymmetric allylic alkylation

A series of modular chiral β-chalcogen amides have been efficiently synthesized from inexpensive and easily available 2-oxazolines. All the selenium, sulfur, and tellurium compounds were evaluated as chiral ligands in the palladium-catalyzed asymmetric allylic alkylation. The corresponding alkylated products were obtained in excellent enantiomeric excess, using BSA/CH₂Cl₂ as the base/solvent system.     

Synthesis of novel chiral phosphine-triazine ligand derived fromα-phenylethylamine for Pd-catalyzed asymmetric allylic alkylation

A novel chiral phosphine-triazine ligand was synthesized from chiralα-phenylethylamine through a three-step procedure.In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-l-yl pivalate with dimethyl malonate,good enantioselectivity (90% e.e.) was obtained by using this ligand.     

Sterically congested, "roofed" β-iminodisulfides as new chiral ligands for palladium-catalyzed, asymmetric allylic alkylation

The preparation of a new class of "roofed" β-iminodisulfides from sterically congested, conformationally rigid chiral 2-thiazolidinones is described. A functional survey of palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate proved that symmetrical "roofed" β-iminodisulfides are efficient chiral ligands, showing enantioselectivity opposite that associated with chiral "roofed" β-iminothioether ligands.     

Sulfoxides derived from Cinchona alkaloids—chiral ligands in palladium-catalyzed asymmetric allylic alkylation

Phenyl sulfides derived from Cinchona alkaloids, 9-PhS-epi-CD, 9-PhS-epi-QN, 9-PhS-epi-QD, and 9-PhS-QN were oxidized into the corresponding sulfoxides. Regardless of the oxidation system used (NaIO₄, TEMPO/NaOCl, VO(acac)₂/chiral Schiff base/H₂O₂) a similar stereochemical outcome of the oxidation was observed. Four pure epimers of sulfoxides 9-PhSO-epi-CD and 9-PhSO-epi-QN were isolated and fully characterized (X-ray, CD, ¹H NMR-pattern). The chiral sulfoxides as well as the corresponding sulfides and sulfones were tested in the Pd-catalyzed allylic alkylation of dimethyl malonate with rac-1,3-diphenyl-2-propenyl acetate. The sulfoxides obtained from Cinchona alkaloids bearing the additional stereogenic center gave the main product of configuration dependent on the chirality of alkaloid framework only. Similar ees (up to 60%) but significantly higher yields (90%) were obtained as compared to the reaction with the corresponding thioethers. The results were in agreement with nucleophilic attack directed at the allylic carbon located trans to the sulfur atom in the M-shaped intermediate η³-allylpalladium complex.     

Highly enantioselective copper-catalyzed alkylation of β-ketoesters and subsequent cyclization to spirolactones/bi-spirolactones

Cu-catalyzed enantioselective alkylation of β-ketoesters using alcohols for in situ preparation of alkylating reagents is reported. A number of functionalized β-ketoesters containing a quaternary carbon stereocenter are obtained with up to 99% ee. The alkylation products derived from 2-substituted allylic alcohols or their corresponding iodides can then be converted to spirolactones, bi-spirolactones, and related chiral target products.     

Enantioselective construction of all-carbon quaternary spirocenters through a Pd-catalyzed asymmetric intramolecular ipso-Friedel–Crafts allylic alkylation of phenols

A novel catalytic asymmetric synthetic method for making spirocyclohexadienones with an all-carbon quaternary spirocenter was developed based on the Pd-catalyzed intramolecular ipso-Friedel–Crafts allylic alkylation of phenols. When 5 mol % of the Pd catalyst and 12 mol % of (?)-9-NapBN (?)-3e were used, the spirocyclic adduct was obtained with up to 93% ee, albeit with low chemical yield. On the other hand, when using 6 mol% of the Trost ligand (R,R)-3k, the spirocyclic adducts were obtained in good yields with up to 89% ee (diastereoselectivity = 9.2:1).     

Chiral 2-(2-phenylthiophenyl)-5,6,7,8-tetrahydroquinolines: new N–S ligands for asymmetric catalysis: Palladium-catalyzed allylic alkylation and copper-catalyzed cyclopropanation reactions

Diastereomeric pure 2-(2-phenylthiophenyl)-5,6,7,8-tetrahydroquinolines were prepared and assessed in the enantioselective palladium-catalyzed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate and in the copper-catalyzed cyclopropanation of styrene with ethyldiazoacetate. Enantioselectivity up to 63% was obtained.     

Catalytic decarboxylative alkylation of β-keto acids with sulfonamides via the cleavage of carbon-nitrogen and carbon-carbon bonds

An efficient decarboxylative alkylation reaction of β-keto acids with N-benzylic or N-allylic sulfonamides has been developed, for the first time, through sequential cleavage of carbon-nitrogen and carbon-carbon bonds in the presence of 10 mol% of FeCl(3).     

Palladium-catalyzed decarboxylative arylation of potassium cyanoacetate: synthesis of α-diaryl nitriles from aryl halides

A palladium-catalyzed decarboxylative coupling of potassium cyanoacetate with aryl bromides and chlorides is described. The reaction conditions feature the absence of additional strong inorganic bases and provide ester functional group tolerance. With Pd(dba)(2) and XPhos ligand as the catalyst system, α-diaryl nitriles can be obtained in good yields.