Synthesis and reactivity of α-allenylhydroxylamines: a new efficient access to 3,6-dihydro-1,2-oxazines

SmI2-promoted reduction of α-allenyl nitro derivatives 2a–f using controlled conditions provides either 3-amino-4-vinylidenetetrahydrofuran 3a or 3-hydroxylamino-4-vinylidenetetrahydrofurans 4b–f, which undergo intramolecular cyclization consistent with a reverse Cope elimination to afford 3,6-dihydro-1,2-oxazines 5b–f.