Novel methodology for the preparation of five-, seven-, and nine-membered fused rings on C60.

[reaction: see text] The photocycloaddition of dienyl cyclopropanes to C(60) gives a new synthetic approach to yield stereospecifically five-, seven-, and nine-membered [60]fullerene adducts. Our results suggest the formation of a biradical intermediate between the dienyl substrate and C(60). An electron transfer between the triplet excited state of C(60) and the dienyl substrate precedes the formation of the intermediate.