Premium
Stereoselective Synthesis and Physicochemical Properties of Liquid‐Crystal Compounds Possessing a trans ‐2,5‐Disubstituted Tetrahydropyran Ring with Negative Dielectric Anisotropy
Author(s) -
Araki Keisuke,
Yamamoto Tetsuya,
Tanaka Ryoji,
Tanaka Saori,
Ushioda Makoto,
Gotoh Yasuyuki,
Yamakawa Tetsu,
Inoue Munenori
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405495
Subject(s) - tetrahydropyran , ring (chemistry) , stereoselectivity , anisotropy , dielectric , liquid crystal , chemistry , materials science , stereochemistry , crystallography , organic chemistry , physics , catalysis , optics , optoelectronics
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 (Δ ε =−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 Et 2 Zn‐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 Δ ε value is discussed.