Re/Mg Bimetallic Tandem Catalysis for [4+2] Annulation of Benzamides and Alkynes via C‑H/N‑H Functionalization

A rhenium-magnesium
cocatalyzed [4+2] annulation of benzamides
and alkynes via C-H/N-H functionalization is described. The reaction
features a divergent and high level of diastereoselectivities, which
are readily switchable by subtle tuning of reaction conditions. Thus,
a wide range of both cis- and trans-3,4-dihydroisoquinolinones is expediently synthesized in a highly
atom-economical manner. Moreover, mechanistic studies unraveled a
tandem mode of action between rhenium and magnesium in the catalytic
cycles.