Catalyst‐Free (3 + 2) Annulation of Morita–Baylis–Hillman Carbonates With Isoquinolines to Access Functionalized Pyrrolo[2,1‐a]Isoquinolines

A divergent strategy has been developed for the reactions between Morita–Baylis–Hillman (MBH) carbonates and isoquinolines. When MBH carbonates, derived from o ‐acylamino‐aryl aldehydes and acrylonitrile, were reacted with isoquinolines, the reaction proceeded via a (3 + 2) cycloaddition/aromatization pathway to afford a diverse array of completely aromatic pyrrolo[2,1‐ a ]isoquinolines in moderate to good yields (51%–91%) with excellent chemo‐ and regioselectivity. In contrast, when the substrates were changed to MBH carbonates synthesized from o ‐acylamino‐aryl aldehydes and methyl acrylate, and 3,4‐dihydroisoquinolines were employed as reaction partners, the reaction underwent a formal (3 + 2) cycloaddition to provide pyrrolo[2,1‐ a ]isoquinolines bearing two adjacent tertiary stereogenic centers in good yields (up to 93%) with excellent chemo‐, regio‐, and diastereoselectivity (all cases > 25:1 dr). Notably, these reactions proceeded under nearly identical reaction conditions, with no observable competitive side products.