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Activated Alkenes (activated + alkene)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

The Substrate Spectra of Pentaerythritol Tetranitrate Reductase, Morphinone Reductase, N -Ethylmaleimide Reductase and Estrogen-Binding Protein in the Asymmetric Bioreduction of Activated Alkenes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Nicole
Abstract Four flavoproteins from the old yellow enzyme (OYE) family, pentaerythritol tetranitrate (PETNR) reductase, N -ethylmaleimide reductase (NEMR), morphinone reductase (MorR) and estrogen-binding protein (EBP1), exhibited a broad substrate tolerance by accepting conjugated enals, enones, imides, dicarboxylic acids and esters, as well as a nitroalkene and therefore can be employed for the asymmetric bioreduction of carbon-carbon double (CC) bonds. In particular, morphinone reductase and estrogen-binding protein often showed a complementary stereochemical preference in comparison to that of previously investigated OYEs. [source]

A Highly Diastereoselective Tertiary Amine-Catalyzed Cascade Michael,Michael,Henry Reaction between Nitromethane, Activated Alkenes and ,,,-Unsaturated Carbonyl Compounds

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010
Bo Zhang
Abstract A new tertiary amine-catalyzed cascade Michael,Michael,Henry reaction between nitromethane, a doubly activated alkene and an ,,,-unsaturated carbonyl compound is described, which provides a convenient and efficient synthesis for densely functionalized cyclohexanes and some bicyclic compounds in moderate to excellent yields with high diastereoselectivity. [source]

Asymmetric Reduction of Activated Alkenes by Pentaerythritol Tetranitrate Reductase: Specificity and Control of Stereochemical Outcome by Reaction Optimisation

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009
Anna Fryszkowska
Abstract We show that pentaerythritol tetranitrate reductase (PETNR), a member of the ,ene' reductase old yellow enzyme family, catalyses the asymmetric reduction of a variety of industrially relevant activated ,,,-unsaturated alkenes including enones, enals, maleimides and nitroalkenes. We have rationalised the broad substrate specificity and stereochemical outcome of these reductions by reference to molecular models of enzyme-substrate complexes based on the crystal complex of the PETNR with 2-cyclohexenone 4a. The optical purity of products is variable (49,99% ee), depending on the substrate type and nature of substituents. Generally, high enantioselectivity was observed for reaction products with stereogenic centres at C, (>99% ee). However, for the substrates existing in two isomeric forms (e.g., citral 11a or nitroalkenes 18,19a), an enantiodivergent course of the reduction of E/Z -forms may lead to lower enantiopurities of the products. We also demonstrate that the poor optical purity obtained for products with stereogenic centres at C, is due to non-enzymatic racemisation. In reactions with ketoisophorone 3a we show that product racemisation is prevented through reaction optimisation, specifically by shortening reaction time and through control of solution pH. We suggest this as a general strategy for improved recovery of optically pure products with other biocatalytic conversions where there is potential for product racemisation. [source]

ChemInform Abstract: Platinum-Catalyzed Reductive Coupling of Activated Alkenes under Hydrogenation Conditions.

CHEMINFORM, Issue 3 2009
Harim Lee
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]

Cobalt-Catalyzed Reductive Coupling of Saturated Alkyl Halides with Activated Alkenes.

CHEMINFORM, Issue 23 2006
Paritosh Shukla
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]

Pd-Catalyzed One-Pot Coupling of Allylamines, Activated Alkenes, and Unsaturated Halides (or Triflate): An Atom-Efficient Synthesis of Highly Functionalized Pyrrolidines.

CHEMINFORM, Issue 12 2005
Luc Martinon
No abstract is available for this article. [source]

Rhodium-Catalyzed Heck-Type Coupling of Boronic Acids with Activated Alkenes in an Aqueous Emulsion.

CHEMINFORM, Issue 51 2004
Mark Lautens
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Nickel-Catalyzed Mizoroki,Heck- versus Michael-Type Addition of Organoboronic Acids to ,,,-Unsaturated Alkenes through Fine-Tuning of Ligands

CHEMISTRY - AN ASIAN JOURNAL, Issue 11 2007
Pao-Shun Lin
Abstract Various arylboronic acids reacted with activated alkenes in the presence of [Ni(dppe)Br2], ZnCl2, and H2O in CH3CN at 80,°C to give the corresponding Mizoroki,Heck-type addition products in good to excellent yields. Furthermore, 1,equivalent of the hydrogenation product of the activated alkene was also produced. By tuning the ligands of the nickel complexes and the reaction conditions, Michael-type addition was achieved in a very selective manner. Thus, various p- and o- substituted arylboronic acids or alkenylboronic acid reacted smoothly with activated alkenes in CH3CN at 80,°C for 12,h catalyzed by Ni(acac)2, P(o -anisyl)3, and K2CO3 to give the corresponding Michael-type addition products in excellent yields. However, for m- substituted arylboronic acids, the yields of Michael-type addition products are very low. The cause of this unusual meta -substitution effect is not clear. By altering the solvent or phosphine ligand, the product yields for m- substituted arylboronic acids were greatly improved. In contrast to previous results in the literature, the present catalytic reactions required water for Mizoroki,Heck-type products and dry reaction conditions for Michael-type addition products. Possible mechanistic pathways for both addition reactions are proposed. [source]

Catalysis by Ionic Liquids: Significant Rate Acceleration with the Use of [pmIm]Br in the Three-Component Synthesis of Dithio­carbamates

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2008
Brindaban C. Ranu
Abstract An easily accessible neutral ionic liquid, 1-methyl-3-pentylimidazolium bromide, promoted a one-pot three-component condensation of an amine, carbon disulfide, and an activated alkene/dichloromethane/epoxide to produce the corresponding dithiocarbamates in high yields at room temperature. The reactions are very fast in ionic liquids relative to those in other reaction media. These reactions do not require any additional catalyst or solvent. The ionic liquid can be recovered and recycled for subsequent reactions. A plausible mechanism is suggested. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

One-pot synthesis of 2H -thiochromenes via TiCl4 -promoted reaction of 2- tert -butylthiobenzaldehydes with activated alkenes

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2009
Chang Hoon Lee
A facile synthesis of 2H -thiochromenes through TiCl4 -promoted reaction of 2- tert -butylthiobenzaldehydes with activated alkenes is described. J. Heterocyclic Chem., (2009). [source]

Nickel-Catalyzed Mizoroki,Heck- versus Michael-Type Addition of Organoboronic Acids to ,,,-Unsaturated Alkenes through Fine-Tuning of Ligands

CHEMISTRY - AN ASIAN JOURNAL, Issue 11 2007
Pao-Shun Lin
Abstract Various arylboronic acids reacted with activated alkenes in the presence of [Ni(dppe)Br2], ZnCl2, and H2O in CH3CN at 80,°C to give the corresponding Mizoroki,Heck-type addition products in good to excellent yields. Furthermore, 1,equivalent of the hydrogenation product of the activated alkene was also produced. By tuning the ligands of the nickel complexes and the reaction conditions, Michael-type addition was achieved in a very selective manner. Thus, various p- and o- substituted arylboronic acids or alkenylboronic acid reacted smoothly with activated alkenes in CH3CN at 80,°C for 12,h catalyzed by Ni(acac)2, P(o -anisyl)3, and K2CO3 to give the corresponding Michael-type addition products in excellent yields. However, for m- substituted arylboronic acids, the yields of Michael-type addition products are very low. The cause of this unusual meta -substitution effect is not clear. By altering the solvent or phosphine ligand, the product yields for m- substituted arylboronic acids were greatly improved. In contrast to previous results in the literature, the present catalytic reactions required water for Mizoroki,Heck-type products and dry reaction conditions for Michael-type addition products. Possible mechanistic pathways for both addition reactions are proposed. [source]