MR0975998 (90d:05156) Fleischner, H. The prism of a 2-connected, planar, cubic graph is Hamiltonian (a proof independent of the four colour theorem). Graph theory in memory of G. A. Dirac (Sandbjerg, 1985), 141–170, Ann. Discrete Math., 41, North-Holland, Amsterdam, 1989.
The review says, in part,
Using the 4CT, the result of the title was shown by M. Rosenfeld and D. W. Barnette [Discrete Math. 5 (1973), 389–394; MR0321806 (48 #173)]. Now the author offers a much longer and more intricate proof, which, however, is 4CT-free.
[So, the connection here is that the first proof of Hamiltonicity relied on the Four Color Theorem, but the newer proof didn't.]