Carbonyl vs Hydroxy: Rhodium catalyzed carbonyl ylide triggered diastereoselective synthesis of 2,5-methano-1,3-benzoxazepines

A general and efficient rhodium catalyzed chemoselective
reaction
of N-sulfonyl-1,2,3-triazoles with 2-hydroxyphenyl
substituted enone has been successfully accomplished. The reaction
occurs through the initial chemoselective reaction of azavinyl carbenes
to the carbonyl group of enone followed by rearrangement and cyclization.
The reaction tolerated various functional groups and allowed the synthesis
of various 2,5-methano-1,3-benzoxazepines in high yield as single
diastereomer. Control experiments revealed the formation of potential
dihydropyrrole as an intermediate and aided in proposing the plausible
mechanism.