Oxidation of N-hydroxyazetidines: A novel synthesis of N-acetoxy β-Lactams and four-membered cyclic nitrones

The N-hydroxyazetidines 2 and 3 are prepared startinfrom 2,3-dihydroazete 1-oxides (1a and 1b 0 by reduction with sodium borohydride and by reaction with a nucleophile, respectively. The N-thydroxyazetidines 2 and 3 can be oxidized with mercury (II) oxide to the corresponding nitrones 1 ; oxidation of the N-hydroxyazetidine 2a (unsubstituted at C-4) with two equivalent of lead tetraacetate tyields the N-tacetoxy β-lactam 4