Fig. 4: Radical 4-exo-dig cyclization of ynamides to azetidines with complex substrates.

Reaction conditions: ynamide 1 (0.2 mmol), [Cu(bcp)DPEphos]PF₆ (5 mol%), (i-Pr)₂NEt (2 mmol), MeCN (0.1 M), r.t., 60 h. Isolated yields are provided and Z/E ratios were determined by ¹H NMR analyses of the crude reaction mixtures.