Tungsten-Enabled Diels–Alder Cycloaddition and Cycloreversion of Arenes and Alkynes: Divergent Synthesis of Highly Functionalized Barrelenes and Arenes

The Diels–Alder reaction of benzenes remains a
significant
synthetic challenge, owing to their highly stabilized aromatic cores.
In this work, the dearomatization agent {WTp(NO)(PMe3)}
is used to promote Diels–Alder reactions of dihapto-coordinated
(η2) benzenes with alkynes. The resulting η2-barrelene complexes can be oxidized to liberate intact barrelenes.
Alternatively, mild pyrolysis leads to the extraction of the corresponding
tungsten-acetylene complex and concomitant formation of new arenes
possessing substituents originating from the acetylene dienophiles.