A rhodium‐catalyzed transannulation of N‐sulfonyl‐1,2,3‐triazoles with carboxylic esters followed by acid‐mediated aromatization has been developed, affording a variety of 2,5‐disubstituted oxazole derivatives in good to high yields under mild reaction conditions. The present transformation is proposed to involve the intermolecular carbonyl ylide formation between in situ generated α‐imino rhodium carbene species and carboxylic esters, which undergoes the nucleophilic attack of the neighboring α‐imino moiety.

An oxidative C–N bond cleavage of cyclic amines has been developed under metal-free conditions, providing N-Cl-ω-amino acids in moderate to excellent yields. The reactions successfully proceed by using tetramethylammonium hypochlorite (TMAOCl) as an oxidant even on a gram scale. The Hofmann–Löffler–Freytag-type reaction of N-Cl-ω-amino acids to form cyclic amino acids are also demonstrated.