Diastereoselective synthesis of bridgehead heterobicyclic spiro compounds derived from tandem Michael intramolecular 1,3-dipolar cycloaddition of nitrones

The reaction of cyclic oximes with divinyl sulfone afforded bridgehead hete robicyclic spiro compounds in good yields. The formation of diastereomerica lly single systems involved conjugate addition of oxime onto the diene sulf one to give transient N-alkenylnitrones that then underwent subsequent intr amolecular dipolar cycloaddition reaction. The diastereoselectivity of the process was predicted by MOPAC AM1 calculations.