Synthesis of α‐Acyloxynitrones and Reactivity towards Samarium Diiodide

Upon treatment of fructose‐derived nitrone 1 with samarium diiodide, with the aim of inducing its umpolung and coupling with electrophiles, an unexpected β‐elimination of the benzyloxy group at C‐1 was observed, yielding nitrone 2 . The mechanism and scope of this transformation were investigated, from nitrone 1 and from five other α‐alkoxy or α‐acyloxy nitrones. This paper describes the preparation of new nitrones 3 and 4 from d ‐fructose; their synthesis demonstrates that acyl‐protected nitrones can be prepared efficiently by intramolecular N ‐alkylation of sugar‐derived oximes, a strategy previously developed only for ether‐ or ketal‐protected cyclic nitrones. Nitrones 3 and 4 underwent fast β‐elimination upon treatment with SmI 2 . Contrastingly, no β‐elimination occurred with nitrones 5 – 7 , suggesting a specific behavior of endocyclic keto nitrones.