|Budget Amount *help
¥7,400,000 (Direct Cost : ¥7,400,000)
Fiscal Year 1995 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1994 : ¥6,400,000 (Direct Cost : ¥6,400,000)
(1) Synthesis, Structure, and Transannular pi-pi Interaction of Multibridged [3_n] cyclophanes
[3_6] (1,2,3,4,5,6) cyclophane 1, which is one of the ultimate compound in the field of [3.3] cyclophane chemistry has been synthesized and characterized. We expect 1 to have the fascinating chemical and structural features ; the photochemical isomerization of 1 to propella [3_6] prismane 2 has been predicted based on semiempirical MO calculations. For the synthesis of 1, we examined a stepwise approach starting from [3_3] (1,3,5) cyclophane. The key to the successful synthesis of 1 lay in employing intramolecular aldol condensation between an acetyl group and a pseudogeminally substituted formyl group to construct an additional bridge. This reaction provided enones in very high yields and the enones were readily reduced to trimethylene bridges by way of ketones. Hexabridged ketone, however, could not be reduced by various metal hydrides, but the employment of SmI_2 in THF in the presence of 1
N aqueous KOH successfully gave the alcohol, which was readily reduced by LiAlH_4-AlCl_3 to give the desired 1.
Electronic absorption bands of [3_n] cyclophanes (n=6,5,4,3) 1,2,3,4 and their charge transfer (CT) bands with tetracyanoethylene (TCNE) in CHCl_3 shift to longer wavelength region with the increase of the number of trimethylene bridges. These results suggest that 1-4 tend to have stronger transannular pi-pi interaction as the number of trimethylene bridges increases. The CT band of 1 (710 nm) is the longest wavelength among those of the CT complexes, of [m. n] cyclophanes and multibridged benzenophanes with TCNE.In the variable temperature ^1H NMR spectra of 1 (toluene-d_8), the energy barriers for the trimethylene bridge inversion process are estimated to be 9.8 kcal/mol. The compound 1 is sensitve to light, and the isolation and identification of the photo-product is in progress.
(2) A Synthetic Study of Double-layred Annulene Containing Two 15,16-Dimethyldihydropyrene Skeletons
In a synthesis of double-layred annulene containing two 15,16-dimethyldihydropyrene skeletons as a model compound for the study of transannular pi-pi interaction, we found that 7,15-di-t-butyl -4,12-dimethyl [2,2] metacyclophane is converted to 2,7-di-t-buty1-15,16-dimethyldihydropyrene in good yield by photo-irradiation in acetic acid. When acetic acid solution of a dimer of the cyclophane, a precursor to the desired double-layred annulene, was irradiated with a low-pressure Hg lamp, the characterictic ^1H NMR signal of the methyl protons of the desired compound was observed. The characterization of the product is in progress.