Synthesis of a C₇₀ Fragment Buckybowl C₂₈H₁₄ from a C₆₀ fragment sumanene

A C₇₀ fragment (1) (C₂₈H₁₄) was synthesized by conversion of a C₆₀ fragment sumanene, via ring expansion and annulation in 3 steps, the key step being the WagnerMeerwein rearrangement of a five-membered ring to a six-membered one. Both theoretical and experimental investigations exhibited the shallower bowl structure of 1, resulting in the lower bowl inversion barrier than sumanene. It was also revealed that the indenopyrene skeleton largely contributed to the physical properties of 1.