Topologically driven tandem radical cyclization-based strategy for the synthesis of oxa- and aza-cages

Tandem radical cyclization-based strategy for the synthesis of oxa- and aza-cage compounds is described. The aryl iodides 1 and N-tosyl propargylated amine 8 lead to oxa- and aza-cages, respectively, after two tandem 5-exo-trig radical cyclizations. The alcohols 11 on reaction with ⁿBu₃SnH and AIBN give rise to the oxa-cages 14 bearing the tributyltin moiety after three tandem 5-exo-trig cyclizations. On the other hand, reaction of the propargyl ether 16 under similar conditions furnishes the oxa-cage 17 by a 5-exo-trig, 4-exo-trig, 5-exo-trig tandem radical cyclization sequence.