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№ 25

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А.С. Носков Учиться, учиться и учиться ...катализу

Премии и награды по химии

Beyond the Molecular Frontier

Семинар
"Современное состояние и перспективы промышленной реализации результатов научных исследований"

Фомичев Ю.П.
"Государственная политика в области правовой охраны, защиты, управления и коммерциализации интеллектуальной собственности"

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"Чтобы ориентироваться в современных реалиях"




Учиться, учиться и учиться ...катализу

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Премии и награды по химии

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Beyond the Molecular Frontier

Подробнее


Современное состояние и перспективы промышленной реализации результатов научных исследований

Подробнее


Государственная политика в области правовой охраны, защиты, управления и коммерциализации интеллектуальной собственности

Подробнее


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Face selectivity of catalyst can be flipped by changing the metal

Last year, chemistry professor Masakatsu Shibasaki and coworkers at the University of Tokyo developed an efficient catalytic enantioselective reaction for cyanosilylation of ketones [J. Am. Chem. Soc., 122, 7412 (2000)]. The catalyst is titanium with ligands derived from an inexpensive starting material, D-glucose. Now, collaborative work between Shibasaki"s group and that of Dennis P. Curran, a chemistry professor at the University of Pittsburgh, shows that replacing titanium with samarium or gadolinium yields a catalyst whose enantiofacial selectivity is the opposite of the original catalyst [J. Am. Chem. Soc, 123, 9908 (2001)]. When the original catalyst is used to prepare a key bicyclic intermediate in the enantioselective synthesis of camptothecins, the R enantiomer is formed. To get the desired S enantiomer (shown), ligands derived from the hugely more expensive L-glucose are needed. Shibasaki"s group discovered that replacing the metal instead provides an alternative route to the S enantiomer. Camptothecins are promising agents for treating solid tumors. Previously, Curran"s group had been preparing the camptodiecin intermediate through asymmetric hydroxylation with osmium, a toxic metal.

C&EN / OCTOBER 8, 2001
http://pubs.acs.org/cen

Rapid, uniform silica deposition

By exposing a surface alternately to vapors of trimethyl-aluminum and tris (tert-butoxy)silanol, Harvard University chemists are able to deposit very thin layers of alumina interspersed between thicker layers of silica at rates more than 100 times faster than those reported for atomic layer deposition (ALD) of silica [Science, 298, 402 (2002)]. The layers are amorphous and highly conformal, meaning that long, narrow holes can be lined or filled uniformly. ALD typically deposits only a partially filled monolayer during each deposition step. By contrast, dozens of silica monolayers are deposited in one step of the new process, developed by chemistry professor Roy G. Gordon and coworkers. The Harvard team proposes that these unexpectedly thick layers of silica grow by a previously unknown catalytic mechanism. This mechanism involves the tethering of an aluminum-oxygen bond to the surface and repeated insertions of silanol into this bond to form a siloxane polymer. The polymer also undergoes cross-linking, eventually solidifying into SiO2. Gordon expects the process to improve the production of microelectronic, optical, and other devices.

C&EN / OCTOBER 14, 2002
http://pubs.acs.org/cen

Hydrotermal ethene synthesis

Mo-V-Te-Nb metal oxide catalysts prepared by hydrothermal synthesis and heat-treated in N2 at high temperatures (600-700oC) exhibit high activity (conversions >80 %) and selectivity (>80 %) for the oxidative dehydrogenation of ethane to ethene (J Lopez Nieto, P Botella, M Vazquez & A Dejoz, Chem Commun 2002, 1906). This process could provide an attractive alternative ethene synthesis using a low-cost feedstock.

Monomer insertion into polymers

Appropriate design of the spatial arrangement of functional groups is essential in making functional materials. And, the distance between sequentially spaced functional groups is the most important factor in determining material properties. A novel strategy has been reported (S Motokucho, A Sudo, F Sanda & T Endo, Chem Commun 2002, 1946) for the synthesis of a sequence-ordered polymer. Its repeating thiocarbonyl unit in the main chain can be arranged with a desired distance, by radically induced well-defined insertion of styrene into the polymer main chain. The synthetic strategy involves synthesis of the polymer precursor (5) possessing a trithiocarbonate moiety in the main chain, and insertion of styrene into this chain through reversible-addition fragmentation-chain-transfer. This is the so-called RAFT process, which is highly reliable and widely applied to living radical polymerisation.

Dutch Catalysis - Top Research

Catalysis belongs, together with medical research, among the top research activities in The Netherlands. A citation analysis, performed by the CWTS of Leiden university for the weekly magazine, Elsevier Magazine, ranked the top 20 researchers in The Netherlands. These scientists have more than 5 articles in the top 1% of most cited publications in international reputed journals over the period 1991-1996 (within a 5 year window). Four of them are active in Catalysis: Jacob Moulijn, Delft (8 publications), Piet van Leeuwen, Amsterdam (7), Rutger van Santen, Eindhoven (7) and Bert Meijer, Eindhoven (6), confirming the blossoming research in this discipline. Moulijn has even a "hot-paper" (see below) - a recent article (1997-2000) on original research cited more than 15 times better than average in selected disciplines. None of the top 20 scientists are publicly well-known "experts." The outlook for the future is bright - catalysis and medical research are predicted to again be at the forefront.

Source: Elsevier 58 (11) (March 16, 2002) 86-95 "Hot-paper: W.J.W. Bakker, L.J.P. van den Broeke, F. Kapteijn and J.A. Moulijn, AlChE-J. 43(1997)2203-2214.

Molecular sieving

A so-called "breathing" ionic crystal (2) is prepared by the complexation of the Keggin-type [α-SiW12O40]4- polyoxometalate ion with the large macro cation [Cr3O(OOCH)6(H2O)3]+. The water of crystallisation is easily removed from (2) by evacuation to form a guest-free phase (3). Compound (3) selectively and reversibly binds small alcohols and nitriles smaller than C3, as well as water, and is capable of separating methanol from a mixture of alcohols (S Uchida, M Hashimoto & N Mizuno, Angew Chem Int Ed Engl 2002, 41, 2814).

Silver - silver oxide interconversion

Meanwhile in-situ interconversion of silver and silver oxide nanoparticles in ultra-thin TiO2 films can be achieved for the first time, using hydrogen and oxygen plasmas as redox reagents, which according to researchers should expand their commercial use to a considerable extent - see Scheme 2. [J He, I Ichinose, S Fujikawa, T Kunitake & A Nakao, Chem Commun 2002,1910].

Chemistry&Industry
4 November 2002



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