Racemic indanofan [(+/-)-1] was efficiently converted to enantiopure (S)-indanofan [(S)-1] by a combination of enzymatic resolution and chemical inversion techniques. An additional important technique is the use of an o-xylene complex of a hemiketal (S)-3c as a precursor, which can be quantitatively converted to (S)-indanofan and easily purified by recrystallization from o-xylene. 相似文献
The total syntheses of natural agelastatin A and agelastatin B were accomplished via a strategy that utilized an alkynyliodonium salt --> alkylidenecarbene --> cyclopentene transformation to convert a relatively simple amino alcohol derivative to the functionalized core of the agelastatin system. Subsequent manipulations delivered debromoagelastatin, which served as a precursor to both agelastatin A and agelastatin B. Alkylidenecarbene insertion chemoselectivity issues were explored en route to the final targets. 相似文献
Glycerol is oxidised to glyceric acid with 100% selectivity using either 1% Au/charcoal or 1% Au/graphite catalyst under mild reaction conditions (60 degrees C, 3 h, water as solvent). 相似文献
The first/second examples of partially oxidized 1-D platinum chain compounds consisting of cationic dimer units have been obtained from electro-oxidation of an aqueous solution containing cis-[Pt(NH3)2(OH2)2]2+ and acetate/propionate. The analytical and crystallographic studies reveal the mixed-valency of Pt(2.2+)infinity. The XPS confirms the presence of both Pt(II) and Pt(III). The solid-state physical measurements reveal that they are diamagnetic semiconductors and display a fairly broad, low-energy absorption band in the range of 500-3200 nm. 相似文献
Dendrimeric polyphenylsulfides, -selenides, and -tellurides are prepared in high yield using propyloxy spacers to connect the phenylchalcogeno groups to the dendrimeric core. The selenides and tellurides catalyze the oxidation of bromide with hydrogen peroxide to give positive bromine species that can be captured by cyclohexene in two-phase systems. The corresponding sulfides show no catalytic activity. The increase in the rate of catalysis followed statistical effects for 1, 6, and 12 phenyltelluro groups. However, the increase in the rate of catalysis exceeds statistical contributions for the first few generations with 1, 3, 6, and 12 phenylseleno groups and suggested cooperativity among phenylseleno groups. The increase in catalytic rate was lost upon replacing all but one phenylseleno group with phenoxy groups. On the basis of H2O2 consumed, the dendrimer with 12 phenylseleno groups has a turnover number of >60 000 mol of H2O2 consumed per mole of catalyst. 相似文献
The fate of clusters emitted onto a substrate falls into several categories including repulsion, soft landing, migration, and explosion, depending on the interaction between the cluster and the substrate. This dynamic behavior of the clusters controls thin-film formation processes from clusters such as cluster ion beam deposition and chemical vapor deposition. Here we describe the collision processes of both Al and Au clusters with a kinetic energy of 0.56 eV/atom onto an amorphous SiO2 substrate studied by molecular dynamics simulation, focusing on the dissipation of translational kinetic energy during the collision process. The simulation elucidated that the activation of thermal vibrational energy of the substrate promoted the sticking of the colliding clusters on the substrate. This result suggests that the dissipation of the translational kinetic energy of the colliding cluster is one of the factors that determine the structure formed on a substrate from vapor phase. 相似文献
We report novel nanoporous polyimides formed from jungle‐gym‐type rigid polyimide gels by supercritical CO2 drying. By virtue of supercritical CO2 drying to avoid the collapse of nanostructure, porosity above 90 vol.‐% was achieved. We found a rich variety of nanoporous structures in the range of 50–800 nm such as crisp fragments, minute network, and highly‐connected beads. These characteristic structures were formed by the competitive progress of liquid‐liquid phase separation and crystallization induced due to the two chemical reactions of end‐crosslinking and thermal imidization during gelation.
In the title compound, [Pd(C6H7N2O3)2(C2H8N2)]·5.5H2O, the Pd atom is coordinated by two 1,3‐dimethylbarbiturate anions through a deprotonated tetrahedral carbon and the enolate oxygen. The Pd—N bond length of 2.078 (2) Åtrans to the C atom is shorter than the Pt—N distance of 2.098 (3) Å in the Pt analog. 相似文献