Palladium-Catalyzed Cycloisomerization of 2-Ethynylbiaryls to9-Methylidene Fluorenes

A palladium-catalyzed cycloisomerization of 2-ethynylbiaryls to 9-methylidenefluorenes is described for thefirst time.The cycloisomerization of 2-ethynylbiaryls proceeded smoothly in the presence of weak acid at low temperature to afford 9-methylidenefluorenes in satisfactory to high yields. This new type of cycloisomerization of 2-ethynylbiaryls is operationally simpleand scalable and exhibits high functional-group tolerance. Various synthetically useful functional groups, such as halogen atoms, aswell as formyl, acetyl, methoxycarbonyl, cyano, and nitro groups, remain intact during the cycloisomerization of 2-ethynylbiaryls.

Automated summary

A palladium-catalyzed cycloisomerization of 2-ethynylbiaryls to 9-methylidenefluorenes is described for the first time. This method is operationally simple and scalable, and exhibits high functional group tolerance.