1,3‐Dipolar addition of formonitrile oxide, and hydroxyiminoacetonitrile oxide to some olefins. The synthesis of isoxazolidino[2,3‐ b ]‐Δ 3 ‐l,2,5‐oxadiazolines

The 1,3‐dipolar addition of formonitrile oxide and hydroxyiminoacetonitrile oxide to a variety of olefins is described. The 3‐anti‐aldoximino‐Δ 2 ‐isoxazolines, resulting from the addition of the dimerie hydroxyiminoacetonitrile oxide to the olefinie substrate, undergo base‐catalyzed cyclization to yield novel isoxazolidino[2,3‐ b ]‐Δ 3 ‐l,2,5‐oxadiazolines. The latter products are rearranged to α‐oximino‐γ‐lactones after additional treatment with base.