Photoinduced Cascade Reaction of Ene‐Yne‐Oxazoles with Trimethylsilyl Azide and N‐Iodosuccinamide: Synthesis of Azidyl Spiroindenoxazolones

Abstract An intriguing photoinduced azidation cyclization of ene‐yne‐oxazolones using trimethylsilyl azide (TMSN 3 ) as an azide source and N ‐iodosuccinimide (NIS) as the iodine source provided access to the corresponding iodobenzylidene spiroindenoxazolones in good yields as a 1:1 mixture of diastereomers (d.r. ratio). A simple and mild metal‐free condition was developed by using blue LEDs to induce the formation of the azidyl radical from TMS‐N 3 as an azide source followed by its aza‐1,4‐addition and the ensuing 5 ‐ exo ‐ dig cyclization to forge multiple bond formations of C─C, C─N, and C─I to furnish the desired spiroindenoxazolones.