α‑Nitrosostyrenes as Three-Atom Units for the (3+1) Cyclization Reaction: Facile Access to 2,3-Dihydrodiazete N‑Oxides and Their Diversified Synthetic Conversions

An unprecedented (3+1) cyclization of α-nitrosostyrenes, generated in situ from α-bromooximes, and N-tosyloxycarbamates was developed, which enables the synthesis of a range of structurally unique and hitherto unexplored 2,3-dihydrodiazete N-oxides in moderate to high yields. The products possess a highly strained four-membered ring structure containing two nitrogen atoms. The synthetic applicability of the products was also demonstrated by many important conversions to diverse nitrogen-containing compounds.