Nitrogen‐Radical‐Triggered Trifunctionalizing <i>ipso</i>‐Spirocyclization of Unactivated Alkenes with Vinyl Azides: A Modular Access to Spiroaminal Frameworks

Abstract

Abstract We report an example of non‐dearomative trifunctionalizing ipso ‐spirocyclization of unactivated alkenes through photoredox‐catalyzed, nitrogen‐radical‐triggered cyclization‐trapping‐translocation‐cyclization cascade, providing a single‐step modular access to spiroaminal frameworks through the sequential formation of one C−C bond and two geminal C−N bonds. The developed protocol utilizes not only internal and terminal olefinic oxime esters, but also olefinic amides as nitrogen radical precursors, and features a broad substrate scope, wide functional group compatibility, easy scalability, and potential for product derivatization and late‐stage functionalization of bioactive estrone derivatives. Importantly, the mechanistic studies including DFT calculations indicate that the photocatalytic trifunctionalizing ipso ‐spirocyclization undergoes a radical relay cascade of intramolecular 5‐ exo ‐ trig cyclization, intermolecular radical trapping, 1,5‐hydrogen atom transfer, and sequential 5‐ endo ‐ trig cyclization, which provides another reaction mode of alkenes. magnified image