A significant improvement in Rh-catalyzed hydroformylation of very hydrophobicalkenes was achieved using a biphasic catalyticsystem consisting of a substrate-containing organic phase and a catalyst-containing hydrogel phase [consisting of poly(ethylene glycol) 20000 (PEG20000) and α-cyclodextrin (α-CD)]. The catalytic performance of the Pickering emulsion that resulted from the formation of α-CD/PEG20000
Mixtures of randomly methylated cyclodextrins of various sizes have been evaluated in the rhodium-catalysed hydroformylation of higher olefins in an aqueous biphasic medium. A marked positive non-linear effect on 1-tetradecene conversion is observed when the CD molar ratio in the mixture is modified. The formation of 2 : 1 ternary inclusion complexes between RAME-CDs and the olefin is supposed to be responsible for the extra conversion observed.
displaced upon coordination to rhodiumcomplexes. The efficacy of the resulting Rh-complex coordinated by β-CD-based phosphanes was assessed in Rh-catalyzed hydroformylation of higherolefins. The catalytic system proved to be far more successful and efficient than a system consisting of supramolecularly interacting phosphanes and CDs. The catalytic activity was up to 30-fold higher while the chemo- and regioselectivities
Process for selectively producing 1-phosphorylated sugar derivative anomer and process for producing nucleoside
申请人:——
公开号:US20020193314A1
公开(公告)日:2002-12-19
A desired isomer is selectively prepared by phosphorolyzing and isomerizing an anomer mixture of a 1-phosphorylated saccharide derivative while crystallizing one of the isomers to displace the equilibrium. Furthermore, using the action of a nucleoside phosphorylase, a nucleoside is prepared from the 1-phosphorylated saccharide derivative obtained and a base with improved stereoselectivity and a higher yield. This process is an anomer-selective process for preparing a 1-phosphorylated saccharide derivative and a nucleoside.
Bidentate Ligands by Self-Assembly through Hydrogen Bonding: A General Room Temperature/Ambient Pressure Regioselective Hydroformylation of Terminal Alkenes
room temperature/ambient pressure regioselective hydroformylation of terminalalkenes with low catalyst loadings in good activity. The generality of this catalyst under these conditions was demonstrated for a wide range of structurally diverse alkenes equipped with many important functional groups. Thus, this practical and highly selective hydroformylation protocol, which omits the need for special pressure