Coming Back to the Starting Position of Carbons Traveling in Organic Molecules on Titanium: Merry-Go-Round Reaction

Traveling of carbon atoms in organic molecules was successfully achieved. The six-membered ring of dihydroindenyl moiety on titanium rotated based on the five-membered ring like a merry-go-round. Two carbons at the bridgehead of the dihydroindenyl moiety and the other three carbons of the five-membered ring were monitored by 13C-labeled experiments. The two carbons at the bridgehead moved to the farthest positions with the rotation of the six-membered ring. The intermediate where the two carbons were located at the farthest positions was isolated and fully characterized. Treatment of the intermediate with azobenzene made the two carbons come back to the starting positions. There is another viewpoint on this reaction. When the six-membered ring is fixed and the movement of three carbons of the five-membered ring of the dihydroindenyl moiety on titanium is focused, it was found that those three carbons moved around the six-membered ring and came back to the starting points.