Rhenium-Catalyzed Phthalide Synthesis from Benzamides and Aldehydes via C-H Bond Activation

The [4 + 1] annulation of benzamides and aldehydes for phthalide synthesis was achieved via rhenium-catalyzed C-H activation, which demonstrates an unprecedented reaction pattern distinct from those of other transition-metal catalyses. The reaction also features readily available starting materials, a wide scope for both electro-rich and electro-deficient substrates, and the elimination of homoannulation byproducts.