The regioselectivity of radical cyclization of enamides can be controlled by the difference in the position of the carbonyl group of amide. In this study, we found that 6-endo-trig selective cyclization of alkyl and acyl radical onto enamides gave perhydroquinoline deriveratives. This reaction was applied to the concise synthesis of cylindricine skeleton by using radical cascade involving 5-endo-trig cyclization. We also found that 7-endo-trig selective cyclization of aryl radical onto enamides gave benzazepine deriveratives. This reaction was applied to the synthesis of lennoxamine by using radical cascade involving homolytic aromatic substitution under non-reductive radical conditions. Three-step synthesis of lennoxamine was achieved in 22% overall yield.
