|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1995 : ¥2,300,000 (Direct Cost : ¥2,300,000)
2 (1H) -Thioxo-1-pyridyl 3-methyl-3- (1,4-dimethyl-9-triptycyl) butanoate rotamers were prepared separately from the corresponding carboxylic acids and submitted to thermolyses and photolyses. Thermolyses of the ester in boiling toluene afforded mainly a cyclized compound (5-membered ring compound) which is derived by addition of the formed radical to an unsubstituted benzene ring followed by dehydrogenation for the ap-isomer, whereas the main product was 9-t-butyl-4-methl-1- [(2-pyridylthio) methyl] -triptycene from the sc-isomer, which indicates that the radical rearrangement to the benzylic position is very easy. On the other hand, photolyses of the ap-ester at 5ﾟC in toluene afforded ap-9- [2- (2-pyridylthio) -1,1-dimethylethyl] -1,4-dimethyltriptycene, which is the coupling product of the radical pair in the solvent cage after loss of carbon dioxide, whereas that of the sc-isomer afforded the sc-counterpart of the above mentioned thioether. In both cases, 20-30% of the dimer in th
e case of the ap and 50-60% of the dimer of the benzylic radical in the case of sc were obtained. Theses results indicate that the temperature of decomposition is important in determining the product distribution in addition to the concentraioton of the radicals formed. Indeed, when the decomposition was carried out by irradiation in the solid stae, the only product observed is the colligation product from the alkyl and the thiyl which are encaged in the lattice.
Rotational isomers of t-butyl 3-methyl-3- (substituted 9-triptycyl) peroxy-butanoates were also prepared separately and their thermolyses in boiling toluene were carried out. The rates of decomposition of these compounds were, unexpectedly, almost independent on the 1-ubstituent as well as rotational positions. We attribute the results to the long distance between the 1-substituent and the O-O bond which is to be broken. However, a product derived from colligatio between the formed alkyl radical and the benzyl radical was found in a fir yield in the case of the 1-chloro compound to indicate that the chloro substitutent stabilizes the intermediate radical. Comparing the results with various substituents, we notice that the larger the substituent size, the more abundantly the 5-membered ring compound is formed. This is attributed by the deformaion by the steric effects of the 1-substituent, by which the radical center is pushed into the triptycene skeleton.
Comparison of the thermal decompositions of t-butyl 3-methyl- (1,4-dimethyl-9-triptycyl) peroxybutanoate and those of 2 (1H) -thioxo-1-pyridyl esters reveals that 9-t-butyl-1,4-dimethyltriptycene is formed in a fair yield from the former, whereas such is not detected from the latter, although the latter produces the corresponding carboxylic acid more abundantly than the former. We attribute the results to the radicophilicity of the sulfur compounds which are in the solvent cage as a part of the radical pair, the nature reducing the reactivity of the alkyl radical in the cage. Less