A light-modulating liquid-crystal element comprising two substrates which each has an electrode layer and at least either of which is transparent and a light-modulating layer supported between these substrates, wherein the light-modulating layer comprises a nematic liquid-crystal material and a transparent solid substance, and the nematic liquid-crystal material comprises a compound represented by the following general formula (I) and/or a compound represented by the following general formula (II) and further contains a compound represented by the following general formula (III), the nematic liquid-crystal material being dispersed as independent fine droplets in the transparent solid substance, the fine droplets having an average particle diameter of 0.1-50 μm. (I) (III) (II) (In the formulae, R
1
to R
3
each independently represents C
1-10
alkyl, etc.; A
1
and A
2
each independently represents trans-1,4-cyclohexylene or 1,4-phenylene; and X
1
and X
2
each independently represents cyano, C
1-10
alkyl, etc.)
US4031028A
申请人:——
公开号:US4031028A
公开(公告)日:1977-06-21
US4400059A
申请人:——
公开号:US4400059A
公开(公告)日:1983-08-23
US7923078B2
申请人:——
公开号:US7923078B2
公开(公告)日:2011-04-12
Benzylic C–H Esterification with Limiting C–H Substrate Enabled by Photochemical Redox Buffering of the Cu Catalyst
作者:Dung L. Golden、Chaofeng Zhang、Si-Jie Chen、Aristidis Vasilopoulos、Ilia A. Guzei、Shannon S. Stahl
DOI:10.1021/jacs.3c01662
日期:2023.5.3
Copper-catalyzed radical-relay reactions provide a versatile strategy for selective C–H functionalization; however, reactions with peroxide-based oxidants often require excess C–H substrate. Here, we report a photochemical strategy to overcome this limitation by using a Cu/2,2′-biquinoline catalyst that supports benzylic C–H esterification with limiting C–H substrate. Mechanistic studies indicate that
铜催化的自由基中继反应为选择性 C-H 官能化提供了一种通用策略;然而,与过氧化物基氧化剂的反应通常需要过量的 C-H 底物。在这里,我们报告了一种光化学策略,通过使用 Cu/2,2'-联喹啉催化剂来克服这一限制,该催化剂支持限制 C-H 底物的苄基 C-H 酯化反应。机理研究表明,蓝光照射促进羧酸盐到铜的电荷转移,将静止态 Cu II还原为 Cu I,从而激活过氧化物以生成烷氧基自由基氢原子转移物质。这种“光化学氧化还原缓冲”引入了一种独特的策略来维持自由基接力反应中铜催化剂的活性。