Copper(II)‐Catalyzed [4+1] Annulation of Propargylamines with N , O ‐Acetals: Entry to the Synthesis of Polysubstituted Pyrrole Derivatives

Described herein is the CuCl 2 ‐catalyzed [4+1] annulation of a variety of propargylamines with N , O ‐acetals that function as a C1 unit, leading to the production of polysubstituted pyrrole derivatives. Three important features of the N , O ‐acetal during the [4+1] annulation series via 5‐endo‐dig cyclization are described: an enolizable substituent adjacent to the central sp 3 ‐carbon is required, the central sp 3 ‐carbon displays the functions of both an electrophile and a nucleophile, and liberation of the secondary amine smoothly leads to the aromatization.