Simple and condensed beta-lactams. Part 32. Base- and acid-catalyzed ring expansions of 3-substituted 4-acetylazetidin2-ones and related compounds

On treatment with bases, the C3-C4 bonds of the 3-substituted 4-(1-iminoeth yl)- or 4-acetylazetidin-2-ones 8f, 8g and 8i are cleaved heterolytically t o afford, depending on the nature of the 3-substituent, ring expansion or o ther products (14, 19 and 27, respectively). Related compound 8h undergoes a base-induced ring transformation to afford compound 23 only after oxidati on to the stereoisomeric disulfanes 20. Compound 8d, when treated with HCL, undergoes a ring transformation to pyrrolidin-2-one 32.