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991.
The boundary-value problem of the reflection and transmission of a plane wave due to a slab of an electro-optic structurally chiral material (SCM) is formulated in terms of a 4×4 matrix ordinary differential equation. The SCM slab can be locally endowed with one of 20 classes of point group symmetry, and is subjected to a dc voltage across its thickness (i.e., parallel to the axis of non-homogeneity of the SCM). The enhancement (and, in some cases, the production) of the circular Bragg phenomenon (CBP) by the application of the dc voltage has either switching or circular-polarization-rejection applications in optics. The twin possibilities of thinner filters and electrical manipulation of the CBP, depending on the local crystallographic class as well as the constitutive parameters of the SCM, emerge. 相似文献
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Ken Tsutsumi Dr. Yuuki Yanagisawa Akinori Furutani Dr. Tsumoru Morimoto Dr. Kiyomi Kakiuchi Prof. Takehiko Wada Prof. Tadashi Mori Dr. Yoshihisa Inoue Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(25):7448-7455
Upon diastereodifferentiating the [2+2] photocycloaddition of ethylene to a series of p‐substituted (?)‐8‐phenylmenthyl cyclohexenonecarboxylates, the diastereoselectivity was critically controlled by the nature of the substituent introduced to the chiral auxiliary, and the p‐nitro‐substituted substrate afforded the cycloadducts in 90 % diastereomeric excess (de) and with 97 % isolated yield. Detailed experimental and theoretical conformation analyses revealed that the stacking interaction of the aromatic auxiliary with the cyclohexenone moiety plays the decisive role in determining the substrate conformation and is, therefore, responsible for the dramatic enhancement of the de. Of particular interest, the product de was directly related to the ellipticity of the substrate, enabling us to “predict” the de prior to photoirradiation. 相似文献
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A simple and efficient enantioselective synthesis of chromene, (?)‐(R)‐cordiachromene ( 1 ), and (?)‐(R)‐dictyochromenol ( 2 ) has been accomplished. This convergent synthesis utilizes intramolecular SNAr reaction for the formation of chroman ring, and Seebach's method of ‘self‐reproduction of chirality’ should establish the (R)‐configuration of the C(2) side chain as key steps. 相似文献
999.
Julen MendizabalPedro de March Josep RecasensAlbert Virgili Ángel Álvarez-LarenaJosé Elguero Ibon Alkorta 《Tetrahedron》2012,68(47):9645-9651
Herein we report a protocol for the enantioselective synthesis of the three stereoisomers of 1,1′-(1,1′-binaphthalene-2,2′-diyl)bis(2,2,2-trifluoroethanol) and their characterization. These compounds, that combine axial and central chirality, might present interesting properties for enantiorecognition. Different reduction processes were applied to racemic and enantiopure 1,1′-(1,1′-binaphthalene-2,2′-diyl)bis(2,2,2-trifluoroethanone) allowing the isolation of the corresponding ketols, 2,2,2-trifluoro-1-[2′-(2,2,2-trifluoro-1-hydroxyethyl)-1,1′-binaphthalen-2-yl]ethanone, and the named diols. 相似文献
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