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.