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Allylic Alkylation Reactions (allylic + alkylation_reaction)
Selected AbstractsUnusual Allylpalladium Carboxylate Complexes: Identification of the Resting State of Catalytic Enantioselective Decarboxylative Allylic Alkylation Reactions of Ketones,ANGEWANDTE CHEMIE, Issue 37 2009Nathaniel Prickelnd! Die enantioselektive palladiumkatalysierte decarboxylierende Alkylierung von Ketonenolaten verläuft über ,1 -,-Allylpalladium-Carboxylat-Komplexe wie 1 (Pd,gelb, O,rot, N,blau, P,violett) durch langsamen CO2 -Verlust. An Brausepulver erinnert das Verhalten unreiner Proben von 1, die im festen Zustand ein Gas (vermutlich CO2) ausstoßen und in Lösung aufschäumen. [source] ChemInform Abstract: Novel Chiral P,O-Ligands for Homogeneous Pd(0) Catalyzed Asymmetric Allylic Alkylation Reactions.CHEMINFORM, Issue 37 2008Vanda Raquel Marinho 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] Polymer-Supported Chiral Monodentate Phosphoramidites in Palladium-Catalyzed Allylic Alkylation Reactions.CHEMINFORM, Issue 34 2007Zhi-Dong Jiang 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, please click on HTML or PDF. [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] Dual Amine- and Brønsted Acid-Catalyzed ,-Allylic Alkylation of AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Li-Wen Xu Abstract A very simple method was developed for the direct, palladium-free catalytic ,-allylic alkylation of aldehydes. The direct organocatalytic intermolecular ,-allylic alkylation reaction was mediated by a simple combination of Brønsted acid and enamine catalysis which furnished ,-allylic alkylated aldehydes and cyclohexanone in high yields and chemoselectivities. The reaction conditions are mild and environmental friendly, the process is conducted under an atmosphere of air without the need for dried solvents, and water is the only side product of the allylic alkylation reaction. [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] New Chiral N, 5-Ligands with Thiophenyl at Benzylic Position.CHINESE JOURNAL OF CHEMISTRY, Issue 9 2002Palladium (II)-catalyzed Enantioselective Allylic Alkylation Abstract New chiral N, S-ligands with oxazoline and thiophenyl substituents at benzene ring and benzylic position have been prepared and applied in palladium-catalyzed asymmetric allylic alkylation reaction to provide the product with high yield and entantioselectivity (82%,93% ee). [source] Effects of Extended Aryl-Substituted Bisoxazoline Ligands in Asymmetric Synthesis , Efficient Synthesis and Application of 4,4,-Bis(1-Naphthyl)-, 4,4,-Bis(2-Naphthyl)- and 4,4,-Bis(9-Anthryl)-2,2,-isopropylidenebis(1,3-oxazolines)EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2005Hester L. van Lingen Abstract The steric influence of extended aryl substituents on 2,2,-bis(1,3-oxazoline) ligands was investigated in a series of asymmetric catalytic reactions such as Mukaiyama aldol and Michael reactions, hetero-Diels,Alder processes, and allylic alkylation reactions. 4,4,-(2-Naphthyl)- and 4,4,-(9-anthryl)-substituted isopropylidene-bridged 2,2,-bis(1,3-oxazolines) were synthesized and their enantioselective and catalytic properties in combination with different metals evaluated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] | |||||||||||||||||||