Lewis acid-catalyzed atom transfer radical cyclization of unsaturated β-keto amides

The Lewis acid-catalyzed atom transfer radical cyclization reactions of olefinic α-bromo β-keto amides were investigated. It was found Lewis acid Yb(OTf)3 or Mg(ClO4)2 not only promoted the cyclization reactions, but also resulted in excellent trans stereocontrol in the cyclization products. With the catalysis of Lewis acid Yb(OTf)3 or Mg(ClO4)2 at −78°C in the presence of Et3B/O2, the cyclization reactions of C-olefinic β-keto amides provided cyclic ketones, while the cyclization reactions of N-olefinic β-keto amides led to the formation of γ-lactams, which could be converted to 3-aza-bicyclo[3,1,0]hexan-2-ones.