[1-60(2] AND [3+2] CYCLOADDITION REACTIONS OF VINYLCARBENES WITH C)

Thermolysis of a mixture of C60 and the cyclopropenone acetal 1a or 1b gives the methanofullerene 4a or b, whereas the ethyl-substituted com pound le gives the cyclopentenone acetal 6. The thermal stability of 4 and the semi-empirical molecular orbital calculations performed for t he parent methanofullerenes and fulleroids indicated that the fulleroi d structure such as 5 may be unstable.