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Phosphoramidite Ligands (phosphoramidite + ligand)
Selected AbstractsAn N -Linked Bidentate Phosphoramidite Ligand (N- Me-BIPAM) for Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to N- SulfonylarylaldiminesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Kazunori Kurihara Abstract A chiral N -linked C2 -symmetric bidentate phosphoramidite (N- Me-BIPAM) was newly developed for the rhodium-catalyzed enantioselective addition of arylboronic acids to N- sulfonylimines. This ligand achieved high enantioselectivities in a range of 84,99% ee in additions of arylboronic acids to N- tosyl- and N- nosylarylaldimines. [source] Very Efficient Phosphoramidite Ligand for Asymmetric Iridium-Catalyzed Allylic Alkylation.CHEMINFORM, Issue 4 2005Alexandre Alexakis Abstract For Abstract see ChemInform Abstract in Full Text. [source] The Synthesis of Spirobitetraline Phosphoramidite Ligands and their Application in Rhodium-Catalyzed Asymmetric HydrogenationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2007Xiang-Hong Huo Abstract A racemic 1,1, - spirobitetralin-8,8,-diol (SBITOL) was conveniently synthesized from 3-methoxybenzaldehyde in 26,% yield over 9 steps and resolved via its bis-(S)-camphorsulfonates. The corresponding chiral spirobitetraline monophosphoramidite ligands have been prepared and their rhodium complexes were applied in the asymmetric hydrogenation of dehydroamino esters with good to excellent enantioselectivities (up to 99.3,% ee). [source] Enantioselective Gold Catalysis: Opportunities Provided by Monodentate Phosphoramidite Ligands with an Acyclic TADDOL Backbone,ANGEWANDTE CHEMIE, Issue 11 2010Henrik Teller Besser ohne Ring: Wird die Isopropylidenacetal-Einheit von den bekannten TADDOL-Liganden entfernt, nimmt die Leistung der daraus hergestellten Phosphoramiditliganden in der asymmetrischen Goldkatalyse zu (siehe Schema; Ts=Toluol-4-sulfonyl). Kristallographisch wurden eine Bindetasche mit dreizähliger Symmetrie und Wechselwirkungen durch den Raum zwischen den Arenringen des Liganden und dem Goldzentrum ermittelt. [source] ChemInform Abstract: Chiral 1-Phenylethylamine-Derived Phosphine,Phosphoramidite Ligands for Highly Enantioselective Rh-Catalyzed Hydrogenation of ,-(Acylamino)acrylates: Significant Effect of Substituents on 3,3,-Positions of Binaphthyl Moiety.CHEMINFORM, Issue 36 2010Xiao-Mao Zhou Abstract Introduction of phenyl substituents at the phosphoramidite backbone of PEAPhos ligand (PEAPP) significantly increases its catalytic activity in the Rh-catalyzed asymmetric hydrogenation of ,-(acylamino)acrylates. [source] ChemInform Abstract: The Synthesis of Spirobitetraline Phosphoramidite Ligands and Their Application in Rhodium-Catalyzed Asymmetric Hydrogenation.CHEMINFORM, Issue 14 2008Xiang-Hong Huo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Enantioselective Copper-Catalyzed Allylic Alkylation with Dialkylzincs Using Phosphoramidite Ligands.CHEMINFORM, Issue 32 2001Hinke Malda Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Quinaphos and Dihydro-Quinaphos Phosphine,Phosphoramidite Ligands for Asymmetric HydrogenationCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2010Thomas Pullmann Dr. Abstract New derivatives of the Quinaphos ligands and the related Dihydro-Quinaphos ligands based on the more flexible 1,2,3,4-tetrahydroquinoline backbone have been prepared and fully characterised. A general and straightforward separation protocol was devised, which allowed for the gram-scale isolation of the Ra,Sc and Sa,Rc diastereomers. These new phosphine,phosphoramidite ligands have been applied in the Rh-catalysed asymmetric hydrogenation of functionalised olefins with the achievement of excellent enantioselectivities (,99,%) in most cases and turnover frequency (TOF) values of up to ,20,000,h,1. These results substantiate the practical utility of readily accessible Quinaphos-type ligands, which belong to the most active and selective category of ligands for Rh-catalysed hydrogenation known to date. [source] Asymmetric Hydrogenation of Quinoxalines Catalyzed by Iridium/PipPhosADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Abstract A catalyst made in situ from the (cyclooctadiene)iridium chloride dimer, [Ir(COD)Cl]2, and the monodentate phosphoramidite ligand (S)-PipPhos was used in the enantioselective hydrogenation of 2- and 2,6-substituted quinoxalines. In the presence of piperidine hydrochloride as additive full conversions and enantioselectivities of up to 96% are obtained. [source] Rhodium-Catalyzed Asymmetric [5+2] Cycloaddition of Alkyne,VinylcyclopropanesCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2009Ryo Shintani Dr. Easy to scale: A rhodium-catalyzed asymmetric intramolecular [5+2] cycloaddition of alkyne,vinylcyclopropanes has been developed. High enantioselectivities of up to >99.5,% ee have been achieved by the use of a chiral phosphoramidite ligand. The reaction can be easily scaled up and the stereochemical model of the present catalysis has also been proposed. [source] Bulky Monodentate Phosphoramidites in Palladium-Catalyzed Allylic Alkylation Reactions: Aspects of Regioselectivity and EnantioselectivityCHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2004Maarten D. K. Boele Dr. Abstract A series of bulky monodentate phosphoramidite ligands, based on biphenol, BINOL and TADDOL backbones, have been employed in the Pd-catalysed allylic alkylation reaction. Reaction of disodium diethyl 2-methyl malonate with monosubstituted allylic substrates in the presence of palladium complexes of the phosphoramidite ligands proceeds smoothly at room temperature. The regioselectivities observed depend strongly on the leaving group and the geometry of the allylic starting compounds. Mono-coordination occurs when these ligands are ligated in [Pd(allyl)(X)] complexes (allyl=C3H5, 1-CH3C3H4, 1-C6H5C3H4, 1,3-(C6H5)2C3H3; X=Cl, OAc). The solid-state structure determined by X-ray diffraction of [Pd(C3H5)(1)(Cl)] reveals a non-symmetric coordination of the allyl moiety, caused by the stronger trans influence of the phosphoramidite ligand relative to X,. In all of these complexes, the syn,trans isomer is the major species present in solution. Because of fast isomerisation and high reactivity of the syn,cis complex, the major product formed upon alkylation is the linear product, especially for monosubstituted phenylallyl substrates in the presence of halide counterions. In the case of biphenol- and BINOL-based phosphoramidites, however, a strong memory effect is observed when 1-phenyl-2-propenyl acetate is employed as the substrate. In this case, nucleophilic attack competes effectively with the isomerisation of the transient cinnamylpalladium complexes. The asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate afforded the chiral product in up to 93,% ee. Substrates with smaller substituents gave lower enantioselectivities. The observed stereoselectivity is explained in terms of a preferential rotation mechanism, in which the product is formed by attack on one of the isomers of the intermediate [Pd{1,3-(C6H5)2C3H3}(L)(OAc)] complex. [source] Enantioselective Synthesis of Chiral Tetrahydroisoquinolines by Iridium-Catalyzed Asymmetric Hydrogenation of EnaminesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Pu-Cha Yan Abstract Chiral iridium complexes based on spiro phosphoramidite ligands are demonstrated to be highly efficient catalysts for the asymmetric hydrogenation of unfunctionalized enamines with an exocyclic double bond. In combination with excess iodine or potassium iodide and under hydrogen pressure, the complex Ir/(Sa,R,R)- 3a provides chiral N -alkyltetrahydroisoquinolines in high yields with up to 98% ee. The L/Ir ratio of 2:1 is crucial for obtaining a high reaction rate and enantioselectivity. A deuterium labeling experiment showed that an inverse isotope effect exists in this reaction. A possible catalytic cycle including an iridium(III) species bearing two monophosphoramidite ligands is also proposed. [source] Quinaphos and Dihydro-Quinaphos Phosphine,Phosphoramidite Ligands for Asymmetric HydrogenationCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2010Thomas Pullmann Dr. Abstract New derivatives of the Quinaphos ligands and the related Dihydro-Quinaphos ligands based on the more flexible 1,2,3,4-tetrahydroquinoline backbone have been prepared and fully characterised. A general and straightforward separation protocol was devised, which allowed for the gram-scale isolation of the Ra,Sc and Sa,Rc diastereomers. These new phosphine,phosphoramidite ligands have been applied in the Rh-catalysed asymmetric hydrogenation of functionalised olefins with the achievement of excellent enantioselectivities (,99,%) in most cases and turnover frequency (TOF) values of up to ,20,000,h,1. These results substantiate the practical utility of readily accessible Quinaphos-type ligands, which belong to the most active and selective category of ligands for Rh-catalysed hydrogenation known to date. [source] Bulky Monodentate Phosphoramidites in Palladium-Catalyzed Allylic Alkylation Reactions: Aspects of Regioselectivity and EnantioselectivityCHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2004Maarten D. K. Boele Dr. Abstract A series of bulky monodentate phosphoramidite ligands, based on biphenol, BINOL and TADDOL backbones, have been employed in the Pd-catalysed allylic alkylation reaction. Reaction of disodium diethyl 2-methyl malonate with monosubstituted allylic substrates in the presence of palladium complexes of the phosphoramidite ligands proceeds smoothly at room temperature. The regioselectivities observed depend strongly on the leaving group and the geometry of the allylic starting compounds. Mono-coordination occurs when these ligands are ligated in [Pd(allyl)(X)] complexes (allyl=C3H5, 1-CH3C3H4, 1-C6H5C3H4, 1,3-(C6H5)2C3H3; X=Cl, OAc). The solid-state structure determined by X-ray diffraction of [Pd(C3H5)(1)(Cl)] reveals a non-symmetric coordination of the allyl moiety, caused by the stronger trans influence of the phosphoramidite ligand relative to X,. In all of these complexes, the syn,trans isomer is the major species present in solution. Because of fast isomerisation and high reactivity of the syn,cis complex, the major product formed upon alkylation is the linear product, especially for monosubstituted phenylallyl substrates in the presence of halide counterions. In the case of biphenol- and BINOL-based phosphoramidites, however, a strong memory effect is observed when 1-phenyl-2-propenyl acetate is employed as the substrate. In this case, nucleophilic attack competes effectively with the isomerisation of the transient cinnamylpalladium complexes. The asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate afforded the chiral product in up to 93,% ee. Substrates with smaller substituents gave lower enantioselectivities. The observed stereoselectivity is explained in terms of a preferential rotation mechanism, in which the product is formed by attack on one of the isomers of the intermediate [Pd{1,3-(C6H5)2C3H3}(L)(OAc)] complex. [source] | ||||||||||||||||||||||