The Diels–Alder reaction of various pyrimidine ortho-quinodimethanes generated in situ with C60 gives access to a variety of new fullerodihydroquinazoline derivatives. This variety is increased since substituents on the pyrimidine ring can be easily modified before or after its reaction with C60. Variable temperature 1H NMR spectra provided thermodynamic parameters related to the boat-to-boat interconversion of the cyclohexene ring fused to the fullerene moiety. The mass spectra of the prepared cycloadducts show that the retro-Diels–Alder process takes place easily with elimination of the corresponding diene molecule.