Access to functionalized benzo[b]fluorene/benzo[a]anthracene derivatives through TfOH-promoted tandem isomerization/cyclodehydration

Abstract

We report a new and efficient protocol to access a series of functionalized benzo[b]fluorenes and benzo[a]anthracenes via triflic acid mediated tandem isomerization/cyclodehydration of formyl bearing 1-benzylidene-2,3-dihydroindene/1-benzylidene-tetrahydronaphthalene derivatives. A palladium-catalyzed intramolecular domino Heck–Suzuki coupling reaction of alkyne tethered 2-bromobenzene derivatives with 2-formyl phenylboronic acid was employed to obtain the precursor substrates. The key step, tandem isomerization/cyclodehydration, offers advantages such as metal-free and mild reaction conditions, easily accessible starting materials, broad substrate scope, and high yields of the desired products.