Synthesis of 1-hydroxyazetidines and their conversion into 1,4-diacetoxy-2-azetidinones

1-Hydroxyazetidines (5), prepared by reductive cyclization of O-benzyl-β-tosyloxy omines 1 and subsequent debenzylation, can be oxidized selectively either to four-membered cyclic nitrones (6 and 7) or to 1,4-diacetoxy-2-azetidinones (9).