Two-carbon ring expansion of β-lactams via N(1)C(4) cleavage reactions

The base-catalyzed ring opening of 4-(4′-hydroxyphenyl)-azetidine-2-ones with potassium tert-butoxide in the presence of tert-butyl methyl malonate gave 1,3,4,5-substituted glutarimides in a simple and efficient manner. The glutarimides were formed stereoselectively depending on the size of the 3-substituent of the β-lactam.