|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1997 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Synthetic efforts towards a series of compounds, which have cylopentene rings enclosing a cyclooctene ring as the core, such as di-, tri-, and tetracyclopentacyclooctanes and their ionic species, were reported.
A synthetic route to dicyclopenta[a,d]cyclooctene (1) was established. This hydrocarbon 1 shows an aromatic character in its NMR spectra and, judging from coupling constants of vicinal protons, 1 is estimated to have a symmetrical completely planar structure without bond alternation. Electrochemical properties of 1 clearly shows its oxidizable and reducable nature. It should be noted that a thermoheater and a gas chromatography apparatus obtained by this grant were very useful in our synthetic efforts to 1. Synthesis of dicyclopenta[a,c]cyclooctene (2) was attempted by two routes. One of them is a sequence which involves dimerization of 6-dimethylaminofulvene at the 1 position, substitution of one of dimethylamino groups with a vinyl group of the dimer, 14π-electrocyclization, an
d subsequent deamination. Although the nickel-catalized dimerization of 2-chloro-6-dimethylaminofulvene was succeeded, substitution of the dimethylmino group with a vinyl one met with little success. On the other hand, an approach by cycloaddition between thialene S,S-dioxide (cyclopenta[b]thiapyrane S,S-dioxide)and 6-dimethylaminofulvene to 2 was also planned. Though a novel synthetic route to thialene was explored by addition-elimination reaction of sulfur and 6-(2-di-methylaminovinyl)fulvene, its yield was not good enough to use in a next reaction.
A novel, divergent synthetic approach to tri- and tetracyclopentacyclooctanes was also studied. The method employed pentafulvalenyl dianion as an active reaction species and, however, in spite of tremendous efforts its condensation with various dicarbonyl compounds was not succeeded. Further synthetic study in vinylogous dicyclohepta[a,e]cyclooctene (3) starting from 3,4-bis(bromomethyl)cycloheptatriene was discloed. Cycloaddition of 6,7-dimethylenecyclohepta-1,4-diene with 3,6,9-trihydrocyclohepta[d] 1,2-dithiin provided 3,6,8,11,14,16-hexahydrodicyclo[c,h][1,6]dithiecin (4), which is a prospective intermediate for synthesizing 3, and whose structure was confirmed by X-ray crystallographic analysis.
Difference of absorption spectra between dicyclopenta[a,c]- and [a, e]cyclooctenes was discussed based on results of semiempirical and ab initio calculations.