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Efficient Reaction (efficient + reaction)
Selected AbstractsOxidation of Aromatic Aldehydes and Ketones by H2O2/CH3ReO3 in Ionic Liquids: A Catalytic Efficient Reaction to Achieve Dihydric Phenols.CHEMINFORM, Issue 25 2005Roberta Bernini No abstract is available for this article. [source] Productive Asymmetric Styrene Epoxidation Based on a Next Generation Electroenzymatic MethodologyADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Reto Ruinatscha Abstract We have established a novel and scalable methodology for the productive coupling of redox enzymes to reductive electrochemical cofactor regeneration relying on efficient mass transfer of the cofactor to the electron-delivering cathode. Proof of concept is provided by styrene monooxygenase (StyA) catalyzing the asymmetric (S)-epoxidation of styrene with high enantiomeric excess, space-time yields, and current efficiencies. Highly porous reticulated vitreous carbon electrodes, maximized in volumetric surface area, were employed in a flow-through mode to rapidly regenerate the consumed FADH2 cofactor required for StyA activity. A systematic investigation of the parameters determining cofactor mass transfer revealed that low FAD concentrations and high flow rates enabled the continuous synthesis of the product (S)-styrene oxide at high rates, while at the same time the accumulation of the side-products acetophenone and phenylacetaldehyde was minimized. At 10,,M FAD and a flow rate of 150,mL,min,1, an average space-time yield of 0.35,g,L,1,h,1 could be achieved during 2,h with a final (S)-styrene oxide yield of 75.2%. At two-fold lower aeration rates, the electroenzymatic reaction could be sustained for 12,h, albeit at the expense of lower (59%) overall space-time yields. Under these conditions, as much as 20.5% of the utilized current could be channeled into (S)-styrene oxide formation. In comparison with state-of-the-art electroenzymatic methodologies for the same conversion, (S)-styrene oxide synthesis could be improved up to 150-fold with respect to both reaction time and space-time yield. These productivities constitute the most efficient reaction reported for asymmetric in vitro epoxidations of styrene. [source] The Use of Samarium Enolates, A Novel Alternative in the Addition Reactions to Imines.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 20094-Diamino Esters, Amides, Enantiopure , Synthesis of 3-Amino Esters Abstract An efficient reaction of tosylimines with a range of samarium enolates (derived from esters, and amides) is reported. The reaction with the ,-dibenzylamino- N - tert- butanesulfinimine derived from chiral phenylalaninal afforded the corresponding enantiopure 3,4-diamino ester with very high diastereoselectivity. [source] Access to Stereodefined Trisubstituted Alkenes via Rhodium-Catalyzed 1,4-Addition of Potassium Trifluoro(organo)- borates to Baylis,Hillman AdductsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2006Laure Navarre Abstract In the presence of a rhodium catalyst, unactivated Baylis,Hillman adducts reacted regioselectively with potassium trifluoro(organo)borates to afford stereodefined trisubstituted alkenes with good yields. This highly efficient reaction (aerobic conditions, low temperature, absence of added phosphane ligand) is believed to proceed via a 1,4-addition/,-hydroxy elimination mechanism. [source] Synthesis of a novel cyclic 5-membered dithiocarbonate (DTC) having hydroxy group and its application to terminal functionalization of polyurethaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2005Suguru Motokucho A novel 5-membered cyclic dithiocarbonate (DTC) having a hydroxy group, 5-hydroxymethyl-1,3-oxathiolane-2-thione (DTC-OH), was synthesized from glycidol. On the basis of the highly efficient reaction of its hydroxyl group with isocyanate, a polyurethane having isocyanate terminals was modified with DTC-OH into a new type of polyurethane prepolymer having DTC-terminals, which was highly reactive with amines but tolerant to moisture. [source] In the Search of Glycogen Phosphorylase Inhibitors: Synthesis of C- D -Glycopyranosylbenzo(hydro)quinones , Inhibition of and Binding to Glycogen Phosphorylase in the Crystal,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2007Li He Abstract Penta- O -acetyl-,- D -glycopyranoses and 1,4-dimethoxybenzene led selectively by electrophilic substitution to C-,- D -glycopyranosyl-1,4-dimethoxybenzenes which were converted by simple and efficient reactions (oxidation, reduction and deacetylation) to the corresponding C-glycosylhydro- and C-glycosylbenzoquinones, with either an acetylated or deprotected sugar moiety. C-,- D -Glucosylbenzoquinone 19 and C-,- D -Glucosylhydroquinone 23 were found to be competitive inhibitors of rabbit muscle glycogen phosphorylase b (GPb), with respect to the substrate ,- D -glucose-1-phosphate, with Ki values of 1.3 and 0.9 mM, respectively, whereas C-,- D -glucosylhydroquinone 17 was not effective up to a concentration of 8 mM. In order to elucidate the structural basis of inhibition, we determined the crystal structures of 19 and 23 in complex with GPb at a 2.03,2.05 Å resolution. The complex structures reveal that the inhibitors can be accommodated at the catalytic site at approximately the same position as ,- D -glucose and stabilise the transition state conformation of the 280s loop by making several favourable contacts to Asp283 and Asn284 of this loop. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] | ||||||||||