1,3‐Dipolar Cycloaddition of Nitrones with Electron‐rich Alkenes Catalyzed by Yb(OTf)3

1,3‐Dipolar cycloaddition of nitrones with ethyl vinyl ether or 2,3‐dihydrofuran proceeds smoothly in the presence of a catalytic amount (10 mol%) of ytterbium triflate to afford isoxazolidines and dicyclic isoxazolidine respectively with good yields and high stereoselectivity.