M. Nishida, H. Fukaya, Yoshio Hayakawa
Jul 1, 2016
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Journal
Asian Journal of Organic Chemistry
Abstract
Hexafluoropropene trimers were reacted with C6F5Si(CH3)3 to provide not only pentafluorophenyl but also perfluorophenylene derivatives [F(C6F4)nC9F17; n=2–9] by successive pentafluorophenylation of perfluoroaryl rings. Their structures, including rotational isomers, were determined by MS, 19F and 13C–{19F} NMR spectroscopy, and/or X-ray crystallography, and were further confirmed by B3LYP-GIAO calculation of NMR shieldings. Formation of a pair of gear-meshed rotamers with clockwise and counterclockwise conformations was identified by NMR measurements for the structures having geminal (CF3)2CF groups at the C=C bond. That the predominantly formed counterclockwise rotamer was gradually converted to the clockwise rotamer over 50 days at room temperature through a synchronized movement of gears was also confirmed by NMR measurements. A comparison between the X-ray structure and B3LYP calculations showed some structural differences that arise from the crystal packing.