An Intramolecular Nitroso-Meerwein–Ponndorf–Verley–Oppenauer Reaction to Access Fused Pyrrolidine Scaffolds

δ-Hydroxy chloronitroso compounds generated in situ from 1,2-oxazine N-oxides undergo a 1,5-hydride transfer related to the Meerwein-Ponndorf-Verley-Oppenauer reaction. Based on the process discovered, a three-step access to fused pyrrolidine scaffolds containing up to four contiguous stereogenic centers starting from simple nitrostyrenes and cycloalkenes or cyclodienes has been developed. The suggested reaction mechanism was confirmed by in situ UV-vis and ATR FT-IR monitoring and DFT calculations.