Diphosphine sulfides derived from 2,2'-biphosphole: novel chiral S,S ligands for palladium-catalyzed asymmetric allylic substitution

Diphosphine sulfides derived from 2,2'-biphosphole have been efficiently synthesized in an enantiomerically pure form by a four step synthetic sequence. These S,S-ligands were used for the first time in Pd-catalyzed asymmetric allylic alkylation. Good yields and enantiomeric excess up to 73% were obtained.     

A new chiral iminophosphine ligand derived from (1S,4S)-fenchone in palladium-catalyzed asymmetric allylic alkylations

A new chiral iminophosphine ligand derived from (1S,4S)-fenchone has been developed, and its usefulness as a chiral ligand in asymmetric synthesis was demonstrated in palladium-catalyzed allylic alkylations.     

A new class of chiral P,N-ligands and their application in palladium-catalyzed asymmetric allylic substitution reactions

An efficient and modular synthesis of a series of chiral nonracemic P,N-ligands is reported. The P,N-ligands were prepared from 2-chloro-4-methyl-6,7-dihydro-5H-[1]pyrindine-7-one and a series of substituted chiral C(2)-symmetric 1,2-ethanediols (R = Me, i-Pr, and Ph). The ligands were evaluated for use in catalytic asymmetric synthesis in the palladium-catalyzed allylic substitution reactions of a racemic allylic acetate and dimethyl malonate. In the case of the P,N-ligand (R = Ph), the reaction was found to be highly stereoselective (90% ee).     

An efficient phosphorus-containing oxazoline ligand derived from cis-2-amino-3,3-dimethyl-1-indanol: application to the palladium-catalyzed asymmetric Heck reaction

Enantiopure 2-[2-(diphenylphosphino)phenyl]oxazoline, derived from a non-natural chiral aminoalcohol, cis-2-amino-3,3-dimethyl-1-indanol, was found to be an efficient ligand for the palladium-catalyzed asymmetric Heck reaction.     

A modular approach to catalyst hydrophobicity for an asymmetric aldol reaction in a biphasic aqueous environment

Catalyst 5, an ion pair consisting of a hydrophilic cation and a lipophilic anion, fulfils the solubility requirements needed to couple efficiency (enantioselectivities and anti-diastereoselectivities up to > or = 99%) and catalyst recyclability in asymmetric aldol reactions under aqueous biphasic conditions.     

A new methodology for synthesis of a chiral phosphinocarboxylic acid through Michael cyclization-aldol tandem reaction of chiral alpha,beta,chi,psi-unsaturated bisphosphine oxide and application in palladium-catalyzed asymmetric allylic alkylation

Upon successive treatment with lithium diisopropylamide and then benzaldehyde, a chiral alpha,beta,psi,omega-unsaturated bisphosphine oxide underwent Michael cyclization-aldol tandem reaction to afford the corresponding endo-alpha,beta-unsaturated cyclic bisphosphine oxides. Sequential stereoselective reduction and Horner-Wadsworth-Emmons olefination gave the corresponding monophosphine oxide. Oxidative conversion of an olefin moiety into a carboxyl group and subsequent deoxygenation of an oxide gave the corresponding chiral phosphinocarboxylic acid, which was successfully applied as a chiral and functionalized monophosphine ligand in a palladium-catalyzed asymmetric allylic alkylation.     

A novel (S)-proline-modified task-specific chiral ionic liquid—an amphiphilic recoverable catalyst for direct asymmetric aldol reactions in water

A novel chiral (S)-proline-modified task-specific ionic liquid has been designed and synthesized as an efficient recoverable organocatalyst for the direct asymmetric aldol reaction between cycloalkanones and aromatic aldehydes in the presence of water. The catalyst retains its activity and selectivity over at least five reaction cycles.     

Synthesis of a novel sterically hindered chiral cyclic phosphoric acid derived from l-tartaric acid and application to the asymmetric catalytic Biginelli reaction

A novel sterically hindered chiral cyclic phosphoric acid derived from l-tartaric acid was designed and synthesized based on highly regioselective cyclosulfitation of chiral 1,1,4,4-tetraphenylbutanetetraol. The asymmetric Biginelli reaction catalyzed by this newly synthesized chiral phosphoric acid was examined, and enantioselectivities up to 99% ee was obtained.     

A novel honeycomb Fe-N-C composition derived from wheat flour as an efficiency catalyst for the oxygen reduction reaction

Journal of Solid State Electrochemistry - Development of efficient, inexpensive, and durable catalysts for oxygen reduction reaction (ORR) is a major challenge for large-scale development of fuel...     

A novel and general synthetic pathway to strychnos indole alkaloids: total syntheses of (-)-tubifoline, (-)-dehydrotubifoline,and (-)-strychnine using palladium-catalyzed asymmetric allylic substitution

A method of palladium-catalyzed asymmetric allylic substitution for synthesizing 2-substituted cyclohexenylamine derivatives was established. Treatment of a 2-silyloxymethylcyclohexenol derivative with ortho-bromo-N-tosylaniline in the presence of Pd(2)dba(3).CHCl(3) and (S)-BINAPO in THF afforded a cyclohexenylamine derivative with 84% ee in 80% yield. The Heck reaction was carried out to produce an indolenine derivative in good yield. Using this method, we synthesized indolenine derivative 7, which was recrystallized from EtOH to give an optically pure compound. From this compound, tetracyclic ketone 13, which should be a useful intermediate for the synthesis of indole alkaloids, could be synthesized. The total syntheses of (-)-dehydrotubifoline, (-)-tubifoline, and (-)-strychnine were achieved from 13. All ring constructions for the syntheses of these natural products were achieved using a palladium catalyst.     

A novel optically active bisphosphine ligand CDP,derived from an anti head-to-head coumarin dimer: synthesis and application to the rhodium-catalyzed asymmetric hydrogenation of arylenamides

A novel optically active bisphosphine ligand CDP containing a C₂-symmetric cyclobutane ring was prepared from an enantiopure anti head-to-head coumarin dimer. CDP was successfully applied to the rhodium-catalyzed asymmetric hydrogenation of arylenamides, affording the corresponding amides up to 93% e.e.     

Synthesis of novel chiral monophosphine ligands derived from isomannide and isosorbide. Application to enantioselective hydrogenation of olefins

A new class of monophosphine ligands has been prepared from natural chirality renewable source, 1,4:3,6-dianhydrohexitol compounds, via a nucleophilic substitution process, or a hydrophosphination reaction involving microwave activation. These ligands have been evaluated for the rhodium-catalyzed enantioselective hydrogenation of olefins giving good conversion and enantioselectivity up to 95% and 96% ee, respectively.     

Nitrosoalkylureas with a quaternary nitrogen atom 8. Study of reaction kinetics of decomposition in an aqueous medium of nitrosoalkylureas derived from alkanediammonium salts

The reaction kinetics was studied of the decomposition in aqueous medium of nitrosoalkylureas (NAU) with antitumorigenic activity, derived from bisquaternary ammonium salts and tertiary diamine hydrochlorides of the general formula

A novel route for in-situ H2O2 generation from selective reduction of O2 by hydrazine using heterogeneous Pd catalyst in an aqueous medium

Hydrogen peroxide in high yields can be generated with high efficiency at mild conditions (25 degrees C and atmospheric pressure) with the formation of only environment-friendly by-products (N2 and H2O) by a reduction of O2 by hydrazine from its hydrate/salt with its complete conversion in a short reaction period (相似文献   

Diastereoselective protonation of lactam enolates derived from (R)-phenylglycinol. A novel asymmetric route to 4-phenyl-1,2,3, 4-tetrahydroisoquinolines

Highly diastereoselective protonation of chiral lactam enolates of 4-substituted-1,4-dihydroisoquinolin-3-ones is reported. Protonation and alkylation processes of these lactam enolates derived from phenylglycinol occur with opposite diastereofacial selectivity. This diastereoselective protonation has been applied to the asymmetric synthesis of (4S)-N-methyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline 9 obtained in up to 97% ee.     

Preparation of novel N-sulfonylated (S,S)-2,3-diaminosuccinate-type chiral auxiliaries and application to an asymmetric 1,3-dipolar cycloaddition reaction of nitrile oxides to allyl alcohol

Novel N-sulfonylated (S,S)-2,3-diaminosuccinate-type chiral auxiliaries, which have the tartaric acid-like framework with a sulfonamide group instead of a hydroxyl group, were synthesized from l-aspartic acid. The synthesized (S,S)-2,3-diaminosuccinate derivatives were applied to an asymmetric 1,3-dipolar cycloaddition reaction of nitrile oxides to allyl alcohol to afford the corresponding optically active 2-isoxazolines, with the enantioselectivities of up to 73% ee. The enantiofacial differentiation was intriguingly opposite to that by using diisopropyl tartrate as a chiral auxiliary.     

A novel axially chiral 2,2'-bipyridine N,N'-dioxide. Its preparation and use for asymmetric allylation of aldehydes with allyl(trichloro)silane as a highly efficient catalyst

[reaction: see text] New axially chiral 2,2'-bipyridine N,N'-dioxides were obtained by a new method that does not involve any procedures for the separation of enantiomers. One of the dioxides, (R)-3,3'-bis(hydroxymethyl)-6,6'-diphenyl-2,2'-bipyridine N,N'-dioxide, exhibited extremely high catalytic activity for the asymmetric allylation of aldehydes with allyl(trichloro)silane. The allylation of aromatic aldehydes proceeded in the presence of 0.01 or 0.1 mol % of the dioxide catalyst to give the corresponding homoallyl alcohols of up to 98% ee.     

Chiral ligands derived from abrine. Part 5: Substituent effects on asymmetric induction in enantioselective addition of diethylzinc to benzaldehyde catalyzed by chiral oxazolidines possessing an indole moiety

A number of the indole-containing chiral oxazolidines possessing the gem-di-p-tolyl and gem-di-o-tolyl groups at C₅ were synthesized from abrine and the effects of the C₅ and C₂ substituents on the asymmetric induction in catalytic enantioselective addition of diethylzinc to benzaldehyde were examined. A working model is proposed to rationalize the asymmetric catalysis by these chiral oxazolidines.     

Metal-promoted allylation, propargylation, or allenylation of azetidine-2,3-diones in aqueous and anhydrous media. Application to the asymmetric synthesis of densely functionalized 3-substituted 3-hydroxy-beta-lactams.

Metal-mediated carbonyl allylation, allenylation, and propargylation of optically pure azetidine-2,3-diones were investigated in both anhydrous and aqueous environments. Different metals promoters showed varied regioselectivities on product formation during allenylation/propargylation reactions of the keto-beta-lactams. The stereochemistry of the new C3-substituted C3-hydroxy quaternary center was controlled by placing a chiral auxiliary at C4. In this way, the coupling of azetidine-2,3-diones with a variety of propenyl-, propynyl-, and allenylmetal reagents offers a convenient asymmetric entry to potentially bioactive 3-substituted 3-hydroxy-beta-lactams.     

A novel polyfunctional chiral building block derived from (S)-ethyl lactate. Application to the synthesis of the sex pheromone of the southern corn rootworm (Diabrotica undecimpunctata howardi)

Highly enantiomerically pure (4S, 5E)-4-bromomethylhept-5-enenitrile was prepared from (S)-ethyl lactate by a six-step procedure involving a rearrangement of chiral cyclopropylcarbinol. This product was used for the synthesis of the sex pheromone of the southern corn rootworm (Diabrotica undecimpunctata howardi), (10R)-10-methyltridecan-2-one. For preliminary communication, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 151–155, January, 2000.