Abstract: The facile stereospecific route is described for synthesizing of 3-hydroxy-4-substituted-2-azetidinones 6.The 2 + 2 cycloaddition of acetoxy acetyl chloride with imine derived from p-anisidine in the presence of triethylamine afforded 3-acetyloxy-4-substituted-l-(4-methoxy-phenyl)-2-azetidinones 3.When the substituents are aryl, aromatic heterocyclic and conjugated alkenyl, the cycloaddition products 3_a-f were cis isomers, while alkoxy and sulfenyl, 3_g, 3_h were trans ones.The oxidation N-dearylation of compounds 3_a-d by using eerie ammonium nitrate (CAN) gave 4_a-d, which were deacetylated with saturated sodium bicarbonate in methanol at room temperature for 1 h to give 6_a-d in good yields.However, under the same N-dearyiation condition, 3_g, 3_h and 3-hydroxy β-lactams 5 did not give the desired N-unsubstituted β-lactams.

Key words: β-Lactam, Azetidinone, Stereospecific synthesis, Deprotection