Copper-Catalyzed Borylative Cyclization of Substituted <i>N</i>‑(2-Vinylaryl)benzaldimines

A <i>t-</i>BuOCu-initiated reaction sequence of styrene borometalation and intramolecular imine addition has been achieved using a Cu­(OTf)₂/dppf combination as catalyst. The product of this reaction cascade is a useful 2,3-disubstituted indoline bearing a versatile boryl moiety and is formed with sole <i>cis</i>-selectivity. To account for the observation of the exclusive formation of <i>cis</i>-stereoisomers, a transition state featuring copper–imine coordination is suggested. The application to the synthesis of antioxidant tetrahydroindenoindoles is described