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Excellent Regio (excellent + regio)
Selected AbstractsAllylation of Aldehyde and Imine Substrates with In Situ Generated Allylboronates , A Simple Route to Enatioenriched Homoallyl AlcoholsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2005Sara Sebelius Abstract Allylation of aldehyde and imine substrates was achieved using easily available allylacetates and diboronate reagents in the presence of catalytic amounts of palladium. This operationally simple one-pot reaction has a broad synthetic scope, as many functionalities including, acetate, carbethoxy, amido and nitro groups are tolerated. The allylation reactions proceed with excellent regio- and stereoselectivity affording the branched allylic isomer. By employment of commercially available chiral diboronates enantioenriched homoallyl alcohols (up to 53,% ee) could be obtained. The mechanistic studies revealed that the in situ generated allylboronates react directly with the aldehyde substrates, however the allylation of the sulfonylimine substrate requires palladium catalysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Aluminium Powder-Catalyzed Regio- and Stereoselective Aminobromination of ,,,-Unsaturated Carbonyl Compounds and Simple Olefins with the p -Toluenesulfonamide/ N -Bromosuccinimide (TsNH2 -NBS) SystemADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Zhan-Guo Chen Abstract The regio- and stereoselective aminobromination of ,,,-unsaturated carbonyl compounds and simple olefins catalyzed by elementary aluminium powder has been established by using p -toluenesulfonamide (TsNH2) and N -bromosuccinimide (NBS) as the nitrogen/bromine sources. The reaction was convenient to carry out with a loading of 1,mol% catalyst at room temperature without inert gas protection. This method provides an easy approach to trans vicinal haloamino derivatives of ,,,-unsaturated carbonyl compounds and simple olefins in high yields (up to 99.8%) and in excellent regio- and stereoselectivities. The electron-rich and electron-deficient olefins show significant differences in activity to the aminobromination reaction and give the opposite regioselectivities. Two possible pathways involving separately a bromonium or an aziridinium intermediate have been proposed. [source] Enantioselective Copper-Catalyzed Allylic Substitution Reaction with Aminohydroxyphosphine LigandADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Naohiko Yoshikai Abstract A proline-derived aminohydroxyphosphine ligand induced excellent regio- and enantioselectivities (SN2,:SN2>94:6, 94,97% ee) in the copper-catalyzed substitution reaction of cinnamyl phosphates with Et2Zn. A computational modelling study of the reaction pathway suggests that the displacement of the leaving group takes place in an ordered, anti -fashion through simultaneous copper,olefin and zinc,oxygen interactions, which is critical for the enantioselection. [source] Copper-Catalyzed Preparation of ,-Alkylidenebutenolides and Isocoumarins under Mild Palladium-Free ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009Samuel Inack-Ngi Abstract A general and efficient copper(I)-catalyzed cross-coupling and heterocyclization reaction of terminal alkynes and ,-iodo-,,,-unsaturated acid derivatives has been developed under very mild conditions. This method provides easy access from good to excellent yields of a variety of 5-ylidenebutenolides and 3-substituted isocoumarins with excellent regio- and stereoselectivity. This procedure does not require the use of any expensive supplementary additives, and is palladium-free. [source] ChemInform Abstract: Synthesis of Dihydrobenzofurans via Palladium-Catalyzed Annulation of 1,3-Dienes by o-Iodoaryl Acetates.CHEMINFORM, Issue 42 2010Roman V. Rozhkov Abstract The widely applicable reaction proceeds with excellent regio- and stereoselectivity. [source] Screening of a Modular Sugar-Based Phosphite,Oxazoline Ligand Library in Asymmetric Pd-Catalyzed Heck ReactionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2007Yvette Mata Abstract We have synthesised a library of phosphite,oxazoline ligands derived from readily available D -glucosamine. These ligands have been successfully screened in the palladium-catalysed Heck reaction of several substrates with high regio- (up to 99,%) and enantioselectivities (ee's up to 99,%) as well as with improved activities under standard thermal conditions. The results indicate that the catalytic performance is highly affected by the oxazoline and biarylphosphite substituents and the axial chirality of the biaryl moiety of the ligand. The Heck reactions were also performed under microwave irradiation conditions, allowing a considerably shorter reaction time (full conversion in minutes) maintaining the excellent regio- and enantioselectivities. [source] | ||||||||||