INTRAMOLECULAR CYCLOADDITIONS AND THERMAL REARRANGEMENT OF CYCLOPROPYLIDENE NITRONES - STRAIGHTFORWARD ACCESS TO BICYCLIC TETRAHYDROPYRIDONES

The intramolecular cycloaddition of cyclopropylidene nitrones (1 and 2 ) gives the ''fused'' adducts exclusively or predominantly over the '' bridged'' adduct (2:1). The ''fused'' adducts posses the cyclopropylox y functionality which is prone to undergo a selective thermal rearrang ement. The adducts 10 and 11 rearrange by heating in solution at 140 d egrees C and 160 degrees C, respectively, to give the bicyclic tetrahy dropyridones 13 and 14.