Enantioselectivities up to 99% ee and excellent yields under mild reaction conditions could be realized in allylic alkylations [Eq. (a)] with palladium catalysts prepared the chiral ligands 1. Enantiomerically pure phosphinoaryldihydrooxazoles (1) are readily accessible from commercially available amino alcohols. HNu = H2C(COOMe)2, H2C(COMe)2, HC(NHAc)(COOEt)2.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChiral semicorrins and related nitrogen heterocycles as ligands in asymmetric catalysisAndreas PfaltzCite this: Acc. Chem. Res. 1993, 26, 6, 339–345Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://pubs.acs.org/doi/10.1021/ar00030a007https://doi.org/10.1021/ar00030a007research-articleACS PublicationsRequest reuse permissionsArticle Views2407Altmetric-Citations571LEARN ABOUT THESE...

Abstract The synthesis of a series enantiomerically pure, C 2 ‐symmetric 4,4′,5,5′‐tetrahydro‐2,2′‐methylenebis[oxazoles] and 4,4′,5,5′‐tetrahydro‐2,2′‐bi(oxazoles) is reported. Copper complexes with anionic tetrahydromethylenebis[oxazole] ligands are efficient catalysts for the enantioselective cyclopropane formation from olefins diazo compounds (up to 96% ee in reaction styrene menthyl diazoacetate). Tetrahydrobi(oxazole)iridium(I) were found catalyze transfer hydrogenations aryl alkyl...

Asymmetric hydrogenation of olefins is one the most useful reactions for synthesis optically active compounds, especially in industry. However, application range catalysts developed so far limited to alkenes with a coordinating functional group or an aryl substituent next double bond. We have found class chiral iridium that give high enantioselectivity unfunctionalized, trialkyl-substituted olefins. Because these do not require presence any particular substrate, they considerably broaden...

Supercritical carbon dioxide (scCO2) was shown to be a reaction medium with unique properties for highly efficient iridium-catalyzed enantioselective hydrogenation of prochiral imines. Cationic iridium(I) complexes chiral phosphinodihydrooxazoles, modified perfluoroalkyl groups in the ligand or anion, were synthesized and tested N-(1-phenylethylidene)aniline. Both side chains lipophilic anions increased solubility, but choice anion also had dramatic effect on enantioselectivity...

Superior bicyclics: Iridium catalysts as 1 derived from pyridine–phosphinite ligands considerably extend the scope of asymmetric hydrogenation. In addition to various unfunctionalized and functionalized olefins, furans, benzofurans, for which no were known before, are also hydrogenated with high enantioselectivity (see scheme). Supporting information this article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z601529_s.pdf or author. Please note: The publisher not...

The branched, chiral products 1 are formed preferentially in the allylic alkylations Equation (1) when Pd catalyst contains P,N ligand L* or derivatives thereof. ligands readily synthesized from commercially available precursors.

Abstract Copper complexes of chiral, C 2 ‐symmetric semicorrin ligands were found to be efficient catalysts for the cyclopropane formation from olefins with diazo compounds. In presence 1 mode‐% catalyst, alkyl diazoacetates reacted smoothly terminal such as styrene, butadiene, and 1‐heptene give corresponding optically active cyclopropanecarboxylic‐acid derivatives (Table Scheme 2) . With one catalysts, enantioselectivities up 97% ee obtained Usually, reactions carried out using...

Factor F430 from Methanogenic Bacteria: Structure of the Porphninoid Ligand System A structure is proposed for F430M, a non‐cristalline methanolysis product isolates nickel‐containing, porphinoid factor Methanobacterium thermoautotrophicum. Crucial to determination are five incorporation experiments with M. thermoautotrophicum (strain Marburg) in which specifically mono‐ 13 C‐labeled biosynthetic precursors (2‐ C), (3‐ (4‐ C)‐, (5‐ C) ALA (ALA = δ‐amino‐levulinic acid) and L‐(methyl‐...

Abstract Cationic iridium complexes with chiral P,N‐ligands and tetrakis[3,5‐(trifluoromethyl)phenyl]borate (BAr F ) as the counterion are efficient homogeneous catalysts for enantioselective hydrogenation of olefins. The readily prepared, air‐stable, easy to handle. In contrast rhodium‐ ruthenium‐phosphine catalysts, they do not require presence a polar coordinating group near CC bond. unfunctionalized arylolefins, high enantioselectivities >95% ee turnover numbers up 5000 frequencies...

Abstract Cationic iridium(I) complexes of chiral phosphanodihydrooxazoles were used as catalysts for the enantioselective hydrogenation prochiral N ‐alkyl and ‐aryl imines. The are air‐stable crystalline solids that can be readily prepared easy to handle. structures two determined by X‐ray analysis. For imines acetophenone, enantiomeric excesses up 79% obtained. Dialkyl ketimines cyclic showed lower reactivity selectivity. A remarkable dilution effect was observed ‐phenyl imine acetophenone:...

Abstract Allylpalladium complexes with chiral bis(dihydrooxazole) ligands were studied as catalysts for the enantioselective allylic substitution reaction of rac ‐1,3‐diphenylprop‐2‐enyl acetate ( ‐ 5 ) anion dimethyl malonate Scheme 1 ). Using enantiomerically pure S , E )‐1‐(4‐tolyl)‐3‐phenylprop‐2‐enyl acatete (( )‐ 25 substrate, was shown to proceed by a clean ‘ syn ’ displacement 6 The [Pd 11 (η 3 ‐allyl)] complex 18 and analogous [Pd(η ‐1,3‐diphenylallyl)] 20 both containing same...

The enantioselective hydrogenation of N-(1-phenylethylidene)aniline using cationic iridium complexes with chiral phosphinooxazoline ligands was studied as a chemical probe to assess the potential ionic liquid/carbon dioxide (IL/CO2) media for, multiphase catalysis. biphasic system leads activation, tuning, and immobilization catalyst that would be impossible in classical organic solvent systems or either two unconventional separately. In particular it is demonstrated (i) presence CO2 can...

For a long time, C(2)-symmetric ligands have dominated in asymmetric catalysis. More recently, nonsymmetrical modular P,N-ligands been introduced. These applied successfully various metal-catalyzed reactions and, many cases, outperformed P,P- or N,N-ligands.

Enantiomeric excesses up to 96% have been obtained in allylic alkylations of 3-aryl-2-propenyl phosphates 2 give 3 with CH(CO2Me) as nucleophile Nu− by using a new tungsten catalyst derived from the phosphanodihydrooxazole complex 1 (X = CH3CN). The regioselectivity is opposite that analogous Pd-catalyzed reactions.

Asymmetric hydrogenation of olefins is one the most important reactions for synthesis optically active compounds, especially in industry. Chiral iridium catalysts based on P,N ligands have strongly expanded their application range. In contrast to rhodium and ruthenium diphosphine complexes they do not require presence a coordinating group near C=C bond and, therefore, allow highly enantioselective hydrogenations largely unfunctionalized alkenes.

Experimental kinetic studies of the coupling p-bromobenzaldehyde (1) with butyl acrylate (2) using dimeric palladacycles complex (4) chelating nitrogen ligands were carried out together modeling a reaction rate expression based on mechanism shown in Scheme 2. The oxidative addition product 1 was found to be resting state within catalytic cycle. formation Pd species external cycle helped rationalize non-first-order dependence catalyst concentration. Theoretical showed how relative...

Optical yields of up to 97% ee characterize the cyclopropanation olefins with diazoacetates in presence semicorrin complex CuL2 (R = CMe2OH). The chiral, C2-symmetrical ligands LH are readily accessible optically pure form from pyroglutamic acid as starting material.

Enantiomeric excesses of up to 99% have been obtained in Heck reactions cyclic olefins with (phosphanyldihydrooxazole)Pd catalysts [Eq. (a)]. In contrast analogous (BINAP)Pd-catalyzed reactions, essentially no isomerization the products by CC bond migration is observed.