Sawada, Tsuyoshi ; Kurokia, Mizue; Ogawaa, Tomoya;  Shimojoa, Kentaro; Chifukua, Kazufumi; Iharaa Hirotaka. Dihydropyrene annelated with dihydrothieno[3.4-b]pyrazine: synthesis and photoswitching property, Tetrahedron Letter (2010),  51(31),  4033-4036.

Sawada, Tsuyoshi; Hongo, Takuya; Matsuo, Nami; Konishi, Masakazu; Kawaguchi, Tsutomu; Ihara, Hirotaka. 

Hemisphere-shaped calixarenes and their analogs: synthesis, structure, and chiral recognition ability.   

Tetrahedron  (2011),  67(25),  4716-4722.

The hemisphere-shaped calixarene 1a and its split-hemisphere-shaped isomer 1b were synthesized from [2.1.2.1]metacyclophane (MCP) 3 by pinacol rearrangement and subsequent intramolecular acetalization. Their structures were revealed by X-ray crystallography and 1H-NMR spectroscopy. The temperature-dependence of the intramolecular acetalization to provide 1a and 1b was examined. The results indicated that 1a is the dominant product at high temperatures, and the values of ΔH˚and ΔS˚ were estimated to be - 18.3 ± 0.37 kJ/mol, - 59.1 ± 1.12 kJ mol-1･K-1, respectively. The dinitro derivative 7 and tetranitro derivatives 8 were obtained by ipso-nitration at the upper rims of 1a. The optical resolution and chiral recognition ability of racemic mixture 7 were investigated by HPLC systems.

9,10-Diacetyl-2,7-di-tert-butyl-trans-10b,10c-dimethyl-10b, 10c-dihydropyrene annelated with a quinoxaline unit (q-DM-DHP, 3) was prepared from 5,13-di-tert-butyl-8,16-dimethyl [2.2]metacyclophane-1,2,9,10-tetraoxide (2) and o-phenylenediamine in two steps. The photochromic isomers of q-DM-DHP 3, closed form 3a and open form 3b, were separated by reverse-phase HPLC, and their isolated UV-visible spectra were estimated. The chiral HPLC analyses of q-DM-DHP 3 indicated their planar chirality, and their CD spectra were measured. The photochromic properties and thermodynamic properties of 3 were also discussed based on their UV-visible, 1H-NMR, CD, and fluorescence spectra.

2,7-Di-tert-butyl-10b,10c-dimethyl-pyrazino[2,3-e]dihydropyrene was prepared and its photochromic properties were studied. The open form of the molecule was separated into its constituent enantiomers by chiral HPLC. The absolute structures of the enantiomers were determined by using spectra predicted with time-dependent density functional theory. Photoswitch- able circular dichroism properties of 2,7-di-tert-butyl-10b,10c-dimethyl-pyrazino[2,3-e]dihydropyrene were observed, suggesting its potential for application in molecular devices.

In this study, 9,10-diacetoxyl-2,7-di-tert-butyl-trans-10b,10c-dimethyl-10b,10c-dihydropyrene annelated with a dihydrothieno[3.4-b]pyrazine unit (1a) was prepared, for the first time, from 5,13-di-tert-butyl-8,16-dimethyl-1,2,9,10-tetrahydroxy[2.2]metacyclophane and 3,4-diaminothiophene in two steps. The photoisomerization property of 1 was investigated by UV and 1H NMR spectroscopies, and the quantitative isomerization between the more stable dihydropyrene (DHP) form and the less stable metacyclophane-diene (MCPD) form was observed. A thermally induced return reaction from the MCPD to the DHP form was examined at various temperatures, and the reaction rate was 0.0049 min−1 at 45 °C, which is slower than that of the parent MCPD.

Asymmetric 2,7-di-tert-butyl-10b,10c-dimethyl-2’,3’-dimethyl-pyrazino[2,3-e]dihydropyrene (DMPZ-DHP) was prepared by annulation of diamino dihydropyrene with 2,3-butanedione. Optical resolution was achieved using chiral high-performance liquid chromatography systems after the photoisomerization of DMPZ-DHP to DMPZ-metacyclophane-diene (MCPD), and its Kuhn’s anisotropy factor g (Δε/ε) was determined to be approximately 1.0 e -3 at 550 nm. When [S]- and [R]-DMPZ-DHP were irradiated with left and right circularly polarized light (CPL) (550 nm), photoisomerization proceeded more rapidly upon irradiating the [S]-isomer with right CPL than with left CPL and upon irradiating the [R]-isomer with left CPL than with right CPL. This suggests the possibility of detecting and analyzing CPL using asymmetric DMPZ-DHP.