Alkylnaphthalenes are not able to form Diels-Alder adducts with C70 fullerene but selected alkylnaphthalenes are able to yield weak charge-transfer complexes (CTC) with C70. More in detail, 1-methylnaphthalene, 2-ethylnaphthalene, and pure naphthalene are not able to produce neither Diels-Alder adducts with C70 fullerene nor CTC. Instead, 1,4-dimethylnaphthalene, 2,6-diethylnaphthalene yield weak 1:1 CTC with C70 fullerene. These CTC are decomposed above ambient temperature. The conjugated diene 2,4-dimethyl-1,3-pentadiene initially forms a weak 1:1 CTC with C70 and evolves into a Diels-Alder multiple adduct where C70 acts as a multisite dienophile.