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[reaction: see text] Arylsilanes were regioselectively labeled with deuterium by treatment with platinum(IV) oxide and deuterium oxide under hydrothermal conditions. Arylsilanols were also labeled with regioselectively under the same conditions. 相似文献
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Yamamoto M Yokota Y Oshima K Matsubara S 《Chemical communications (Cambridge, England)》2004,(15):1714-1715
Benzene rings of polystyrene samples are labelled with deuterium oxide and catalytic amount of platinum(iv) oxide under hydrothermal conditions. 相似文献
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[structure: see text] A convergent total synthesis of khafrefungin was accomplished on the basis of (1) the highly stereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using vinylketene silyl N,O-acetal and (2) syn-selective aldol reaction of enal 5a and ethyl ketone 6 followed by anti-dehydration under Mitsunobu conditions. 相似文献
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Oxacyclic structures such as tetrahydrofuran (THF) rings are commonly found in many bioactive compounds, and this has led to several efforts toward their stereoselective syntheses. However, the process of catalytic asymmetric cycloetherification for their straightforward synthesis has remained a challenge. In this study, we demonstrate a novel asymmetric synthesis method for THF via the catalytic cycloetherification of ε-hydroxy-α,β-unsaturated ketones mediated by cinchona-alkaloid-thiourea-based bifunctional organocatalysts. This catalytic process represents a highly practical cycloetherification method that provides excellent enantioselectivities, even with low catalyst loadings at ambient temperature. 相似文献
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Nickel(0) catalyzed [4+2] cycloaddition of electron-deficient dienes to alkynes and subsequent aromatization gave highly substituted arenes. This formal inverse electron-demand Diels-Alder cycloaddition is attributed to the formation of a seven-membered nickelacycle from a diene and an alkyne. 相似文献
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Wakihara T Kohara S Sankar G Saito S Sanchez-Sanchez M Overweg AR Fan W Ogura M Okubo T 《Physical chemistry chemical physics : PCCP》2006,8(2):224-227
The structure of amorphous precursor species formed under hydrothermal conditions, prior to the onset of crystallization of microporous aluminosilicate zeolites, is determined employing high-energy X-ray diffraction (HEXRD). The investigation, combined with the use of reverse Monte Carlo modelling suggests that even numbered rings, especially 4R (R: ring) and 6R, which are the dominant aluminosilicate rings in zeolite A, have already been produced in the precursor. The model implies that the formation of double 4Rs occurs at the final step of the crystallization of zeolite A. 相似文献
100.
Yoshino H Toda N Kobata M Ukai K Oshima K Utimoto K Matsubara S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(3):721-726
Bis(iodozincio)methane, prepared from diiodomethane and zinc, reacts with an organic halide in the presence of a transition-metal catalyst to give an iodozinciomethylenated compound; this then reacts with another organic halide to form a C--C bond. The overall process connects two electrophiles with one carbon atom. Bis(iodozincio)ethane can also undergo this transformation, yielding a new stereogenic center. The asymmetric induction of this stereogenic center was investigated by using a chiral palladium catalyst. 相似文献