Intramolecular cycloadditions and thermal rearrangement of cyclopropylidene nitrones. Straightforward access to bicyclic tetrahydropyridones

Abstract

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 cyclopropyloxy functionality which is prone to undergo a selective thermal rearrangement. The adducts 10 and 11 rearrange by heating in solution at 140°C and 160°C, respectively, to give the bicyclic tetrahydropyridones 13 and 14.