REACTIVITIES OF STABLE ROTAMERS .39. THERMAL-DECOMPOSITION OF T-BUTYL3-METHYL-3-(SUBSTITUTED 9-TRIPTYCYL)PEROXYBUTANOATE ROTAMERS

The ap and sc rotamers of the title compound, where substituents are 1 ,4-dimethyl, 1,4-dimethoxy, 1,2,3,4-tetrafluoro, and 1,2,3,4-tetrachlo ro, were thermolyzed in toluene solutions to examine the effects of in teractions between the radical center and the substituent. The rates o f thermolyses were affected neither by the substituent nor by the rota meric positions, but the product distributions showed dependence on th e substituent. In the ap-forms, the effectively bulkier the substituen t at the 1-position, the higher the yields of the 5-membered ring comp ound. This was attributed to the degree of the tilting of the 9-substi tuent, which forces the radical center to be pushed into the triptycen e skeleton. For the sc-forms, the chloro and the methyl substituents e xhibited special effects, the former affording a colligation product b etween benzyl and 2-(1,2, 3,4-tetrachloro-9-triptycyl)-2-methylpropyl radicals and the latter showing a tendency of radical migration to the benzylic position. Comparison of the results of thermolyses of the 1, 4-dimethyl peroxyester with those of 2(1H)-thioxo-1-pyridyl 3(1,4-dime thyl-9-triptycyl)-3-methylbutanoate indicates that, although it is bel ieved that these precursors afford the same 2(1,4-dimethyl-9-triptycyl )-2-methylpropyl radicals, the product distributions were significantl y different from each other. These results were attributed to the stab ilizing effects of the sulfur compound on the radical in the solvent c age in the latter.