Chemoselective Double Annulation of Two Different Isocyanides: Rapid Access to Trifluoromethylated Indole-Fused Heterocycles

An unprecedented chemoselective double
annulation of α-trifluoromethylated
isocyanides with o-acylaryl isocyanides has been
developed. This new reaction provides a rapid, efficient, and complete
atom-economic strategy for the synthesis of trifluoromethylated oxadiazino­[3,2-a]­indoles in a single operation from readily available starting
materials. Isocyanide insertion into CO double bonds is disclosed
for the first time as indicated by the results of 18O-labeling
experiment. A mechanism for this domino reaction is proposed involving
chemoselective heterodimerization of two different isocyanides, followed
by indole-2,3-epoxide formation and rearrangement.