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Target Products (target + products)
Selected AbstractsFlexible Route to Palmarumycin CP1 and CP2 and CJ-12.371 Methyl EtherEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010Karsten Krohn Abstract The total synthesis of palmarumycin CP1 (4) and CP2 (5) and racemic CJ-12.371 methyl ether (17) is described using the Diels,Alder reaction of benzoquinone 1,8-dihydroxynaphthalene acetal (10) with 1-methoxy-1,3-butadiene under neat reaction conditions. The stereochemistry of adduct 15 was confirmed by single-crystal X-ray analysis. The transformation of 15 into target products 4, 5, and 17 involved dehydrogenation, methyl ether cleavage, and reduction and oxidation steps. [source] Synthetic and Mechanistic Aspects of Acid-Catalyzed Disproportionation of Dialkyl Diarylmethyl Ethers: A Combined Experimental and Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Margherita Barbero Abstract The disproportionation reactions of various dialkyl diarylmethyl ethers have been carried out in the presence of a catalytic amount (10 mol-%) of o -benzenedisulfonimide as a Brønsted acid catalyst; the reaction conditions were mild, and the yields of the diarylmethane target products were good. The catalyst was easily recovered and purified, ready to be used in further reactions. The theoretical study confirmed that the reaction proceeds in two steps: The formation of a carbocation from the protonated ether followed by hydride transfer. Although the hydride transfer is the rate-determining step, it is the stability of the carbocation that determines the reaction rate and therefore the yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enantioselective One-Pot Two-Step Synthesis of Hydrophobic Allylic Alcohols in Aqueous Medium through the Combination of a Wittig Reaction and an Enzymatic Ketone ReductionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2007Marina Kraußer Abstract A one-pot two-step process for the enantioselective synthesis of hydrophobic allylic alcohols was developed, which comprises ketone formation by the Wittig reaction and their enzymatic in situ biotransformation into the desired target products. By means of this combined Wittig reaction and bioreduction, the allylic alcohols were prepared with conversions of up to 90,%, and with excellent enantioselectivities of >99,% ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Process intensification using a two-phase system and micromixing for consecutive and reversible reactionsAICHE JOURNAL, Issue 6 2009Yoshihito Okubo Abstract This study aimed to find reaction conditions that improve the yield of target intermediate products, using a two-phase system and a microspace for first-order consecutive and reversible reactions. As a result, the yield of target products with a two-phase system can be surpassed by that of a single-phase system through selecting the organic phase such that the partition coefficient of the raw material to the aqueous phase is large, and that of the target product to the organic phase is also large. In addition, the volume ratio of two phases and the liquid,liquid interfacial area are also important factors for improving the target product yield. In a microspace, the microfluid segments can be designed both arbitrarily and precisely, and thus it is possible to control the interfacial area and mass transfer rates accurately. Utilization of a microspace can play a significant role in intensifying a two-phase system. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Transesterification of dimethyl oxalate with phenol over TiO2/SiO2: Catalyst screening and reaction optimizationAICHE JOURNAL, Issue 12 2008Xia Yang Abstract Physicochemical properties of silica-supported titanium oxide catalysts as well as their performances for transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) have been investigated systematically. Various wt % of TiO2 were loaded on SiO2 by a two-step wet impregnation method. The surface properties of TiO2/SiO2 catalysts were explored by various characterization techniques (BET, SEM, ICP, XPS, XRD, FTIR of pyridine adsorption, and NH3 -TPD). Catalytic performances of TiO2/SiO2 catalysts were found to be strongly dependent on TiO2 dispersion and surface acidity. Monolayer dispersion capacity of TiO2 on silica was estimated to be about 4.0 TiO2 molecules per nm2 (SiO2) and no crystalline TiO2 was detected at TiO2 loading less than 12 wt %. FTIR and TPD analysis suggested that weak Lewis acid sites on the surface of TiO2/SiO2 were responsible for their unique selectivity to the target products, MPO and DPO. An optimization of reaction conditions for the transesterification of DMO with phenol was performed over 12 wt % TiO2/SiO2 calcined at 550°C. In addition, we studied the disproportionation reaction from MPO to DPO via a catalytic distillation process, which is highly efficient to promote formation of the desired DPO. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] | ||||||||||