METHANOFULLERENES AND PROPANOFULLERENES BY [1+2] AND [3+2] CYCLOADDITIONS OF VINYLCARBENE SPECIES

Vinylcarbene species generated by thermolysis of cyclopropenone acetal (CPA) reacts with C-60 in a [1+2] and a [3+2] manner to afford, at 80 degrees C, methano- and propanofullerene derivatives as a 10:1 mixture. The periselectivity depends on the reaction temperature; the ratio of the [1+2] and [3+2] cycloadducts changed to 2:1 and to 7:93 in the reaction at 100 and 140 degrees C, respectively. Temperature dependence was also observed in the reaction of phenyl-substituted CPA. The reactions of ethyl- and trimethylsilyl-substituted CPAs, which proceeded only at 150-170 degrees C, afforded propanofullerenes as a sole product. The reaction of the substituted CPAs proceeded exclusively via a terminally substituted vinylcarbene species.