Copper(I)-Catalyzed Syntheses of Benzo[b]fluorenes by the Cascade Reactions of 2-Alkynylbenzaldehyde N-Tosylhydrazones and Aromatic Terminal Alkynes

Benzo[b]fluorenes were synthesized via CuI-catalyzed cascade reactions of 2-alkynylbenzaldehyde N-tosylhydrazones and aromatic terminal alkynes in the presence of base including the formation of the benzoenyne-allene intermediate in situ and its Schmittel cyclization. Density functional theory calculation was performed to give the energy difference for the formation of 5phenyl-11H-benzo[b]fluorene and 1,2-diphenyl-1H-cyclobuta[a]indene from the proposed diradical intermediates.

Automated summary

In this study, benzo[b]fluorenes were synthesized via cascade reactions, involving the formation of the benzoenyne-allene intermediate and its subsequent cyclization. Density functional theory calculation was used to determine the energy difference for the formation of the final products.