title: Isocyanurates with planar chirality: design, optical resolution, and isomerization.
abstract: Designs and syntheses of isocyanurates (1-3) are described on the basis of a novel concept that two enantiotopic faces of C(s) -symmetric, prochiral planar molecules are differentiated with a location of groups at the top or bottom of the planar skeleton using a rigid linker. Such isocyanurates are atropisomeric. The planar-chiral structures of 1 and 2(anti) (anti-conformer of 2) were confirmed by single-crystal X-ray analyses, and the space groups were P1 (for 1) and P2(1)/c (for 2(anti)), resulting that the crystals were racemates. Optical resolutions of 1-3 were successfully accomplished by using chiral high-performance liquid chromatography technique in combination with circular dichroism, absorption, and nuclear magnetic resonance spectroscopies and mass spectrometry. Furthermore, the rotational barriers (ΔG(‡)s) related to isomerizations of 1-3 were estimated to be 27.2 (for 1 at 50 °C), 27.6 (for 2(anti) at 50 °C), and 40.6 (for 3(syn) at 150 °C) kcal/mol. The ΔG(‡)s of 2 and 3 were higher than that of 1 and, in particular, that of 3 was highest among them. This result indicates that an introduction of bulky substituents and an intramolecular bridging are effective for inhibitions of the isomerizations.
authors.affiliation: Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Goto
authors.forename: Masanao
authors.initials: M
authors.lastname: Sudoh
authors.forename: Keiko
authors.initials: K
authors.lastname: Kawamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugimoto
authors.forename: Shohei
authors.initials: S
authors.lastname: Inoue