Dual Gold Catalysis: Synthesis of Fluorene Derivatives from Diynes

Abstract

Abstract1,5‐Diyne systems bearing one terminal and one benzyl‐ or allyl‐substituted alkyne attached to an aromatic backbone were converted in the presence of a gold catalyst. In a dual gold‐catalyzed process, gold vinylidenes are formed that selectively undergo formal CH insertion into the C(sp2)–H bond of the offered unsaturated systems. If H atoms are present in the propargylic position, a subsequent isomerization to the aromatic system takes place leading to 9H‐fluorene and 11H‐benzo[b]fluorene derivatives as final products. In the case of a quaternary carbon in the propargylic position no further aromatization is observed and 10H‐benzo[b]fluorene derivatives are obtained in high yield.magnified image