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.