Formal [(2 + 2) + 2] and [(2 + 2) + (2 + 2)] Nonconjugated Dienediyne Cascade Cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.