Stereoselective Synthesis and Physicochemical Properties of Liquid‐Crystal Compounds Possessing a trans‐2,5‐Disubstituted Tetrahydropyran Ring with Negative Dielectric Anisotropy |
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| Authors: | Dr. Keisuke Araki Dr. Tetsuya Yamamoto Dr. Ryoji Tanaka Makoto Ushioda Dr. Yasuyuki Gotoh Dr. Tetsu Yamakawa Dr. Munenori Inoue |
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| Affiliation: | 1. Sagami Chemical Research Institute (SCRI), 2743‐1 Hayakawa, Ayase, Kanagawa 252‐1193 (Japan);2. JNC Petrochemical Corporation, 5‐1, Goi Kaigan, Ichihara, Chiba 290‐8551 (Japan);3. JNC Corporation, Shin‐Otemachi Bldg. 2‐1 Otemachi 2‐Chome Chiyoda‐ku, Tokyo 100‐8105 (Japan) |
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| Abstract: | Three stereoselective syntheses and the physicochemical properties of trans,trans‐5‐(4‐ethoxy‐2,3‐difluorophenyl)‐2‐(4‐propylcyclohexyl)tetrahydropyran, which is an important liquid‐crystal compound with a large negative dielectric anisotropy (Δε=?7.3), are described. The key step in the construction of the trans‐2,5‐disubstituted tetrahydropyran ring in the first approach involved a benzylic cation mediated intramolecular olefin cyclization of a 2‐allyloxy‐1‐arylethanol derivative. The second method included the Et2Zn‐induced 1,2‐aryl shift of a bromohydrin obtained from a hetero‐Diels–Alder reaction, followed by stereoselective bromination. The third approach utilized the hetero‐Diels–Alder reaction of trans‐4‐propylcyclohexanecarboxaldehyde and a 2‐aryl‐3‐(trimethylsilyl)oxy‐1,3‐butadiene, followed by stereoselective protonation. From results obtained by using a quantum chemical calculation method, the reason why the target compound shows a large negative Δε value is discussed. |
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| Keywords: | cyclization density functional calculations liquid crystals structure– activity relationships synthesis design |
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