We report an ambimodal trispericyclic transition state leading to [6+4]-, [4+6]-, and [8+2]cycloadducts in the reactions of 8,8-disubstituted heptafulvenes with 6,6-dimethylfulvene. The potential energy surfaces for these reactions were explored with omega B97X-D density functional theory. Quasi-classical direct molecular dynamics simulations gave information on the ratios of products expected in these reactions.