Gold-Catalyzed One-Pot A3-Coupling/1,5-Hydride Shift/Schmittel-Type Cyclization: From Aldehydes, Amines and Alkynes to the Synthesis of Benzo[b]fluorenes

Abstract

A step-economic gold-catalyzed one-pot synthesis of benzo[b]fluorenes, from aldehydes, alkynes and amines, proceeding via an A3-coupling/1,5-hydride shift/Schmittel-type cyclization is described. The formation of the allene intermediate is not dependent on a previous installation of reaction triggers, and upon cyclization delivered benzo[b]fluorenes. With this method, just by an easy modification of the starting materials in a modular way, nineteen benzo[b]fluorenes, bearing different substituents Ar1, Ar2 and Ar3, were prepared. Overall, three new carbon–carbon bonds are formed in one-pot.