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101.
102.
[reaction: see text] An H(5)C(5x)-type free-radical chain reaction selectively generates up to three new bonds and three new stereocenters in one pot. This previously unexploited strategy provides a straightforward route to the tricyclic cyclopenta[c]indene skeleton, present in a wide range of pharmacologically active natural products, and can significantly simplify the synthesis of other strained polycyclic structures by sidestepping protection, deprotection, and functional group interconversion steps. 相似文献
103.
Shuhei Yamada Zhifeng Wang Emiko Mouri Kohji Yoshinaga 《Colloid and polymer science》2009,287(2):139-146
We report a novel strategy for incorporation of titanium dioxide (TiO2) particles, which were crystallized from peroxotitanic acid in the presence of hydrophilic polymer by hydrothermal treatment
in aqueous solution, into poly(methyl methacrylate) (PMMA) via dispersion into chloroform. Dispersion of TiO2 particles into chloroform was achieved by solvent change from water to chloroform in aid of amphiphilic polymer dispersant,
poly(N-vinyl pyrrolidone) (PVP), poly(N-vinyl pyrrolidone-co-methyl methacrylate) (PVP-co-PMMA), poly(N-vinyl pyrrolidone-block-methyl methacrylate) (PVP-b-PMMA) through azeotropical removal of water. Incorporation of TiO2 particles into PMMA was carried out by a casting process of a mixture of TiO2 particles dispersed with PVP154-b-PMMA156 in chloroform and PMMA on a glass substrate. Resultant hybrid film containing TiO2 less than 10 wt.% showed high transparency in visible region attributable to homogeneous dispersion into PMMA matrix. The
refractive index of the hybrid films increased with TiO2 content and agreed with the calculated values. 相似文献
104.
A copper-catalyzed gamma-selective and stereospecific substitution reaction of allylic carbonates with a diboron reagent affording allylboron compounds is described. Boryl group was selectively introduced at the gamma-position of the leaving carbonate group. Functionalized allylboronates that have an acetal, ester, or isolated alkene were prepared. The reaction of optically active allylic carbonates underwent complete alpha-to-gamma chirality transfer with anti-stereochemistry to produce optically active allylboronates having a boron-substituted stereogenic center. 相似文献
105.
106.
107.
The strained-layer superlattices (SLS's) of InxGa1?xAsGaAs and the single hetero-structure of InxGa1?xAs on GaAs were grown by MBE method. The samples obtained have a perfect surface morphology. The alloy composition of InxGa1?xAs layer and the growth rate were determined with high accuracy by in situ observation of the intensity oscillation of RHEED pattern. Photoluminescence peak energies of SLS's are in agreement with the calculated value by the Kronig-Penny analysis. 相似文献
108.
A new method which is based on (2-3)-Wittig sigmatropic rearrangements for the stereocontrolled synthesis of functionalized three-carbon side chains on the basic tetracyclic steroidal system is described. 相似文献
109.
Novel analogues of the hormone 1alpha,25-(OH)(2)-D(3) with side chains attached to C-18 were synthesized by a versatile route in which key steps were the remote radical-induced functionalization of the 18-methyl by the C-8beta-hydroxyl group and the introduction of the side chains by Wittig reactions on a C-18-aldehyde. The triene system of the novel analogues was constructed by the convergent Lythgoe-Hoffmann la Roche approach, which involves reaction of a phosphine oxide (the ring A fragment) with a ketone (the upper fragment). 相似文献
110.
[reaction: see text] A mild palladium-catalyzed cascade has been used for the synthesis of the hormone 1alpha,25-dihydroxyvitamin D3 (calcitriol, 1a) and its analogues 1b and 1c. This one-pot process involves two consecutive transformations at room temperature: An initial palladium-catalyzed 6-exo-cyclocarbopalladation of vinyl triflates followed by a Negishi cross-coupling reaction with an alkenyl zinc. This novel strategy opens new possibilities for the preparation of a variety of new vitamin D analogues of therapeutic potential, particularly with modifications at the triene and/or ring-A. 相似文献