Novel syntheses of azetidines and azetidinones

A review on the most recent methods that is used for the synthesis of the four-membered ring systems is given which will highlight the stereoselective methods. The specific topics that will be described include: the cyclizations by nucleophilic substitution of amine nucleophiles and by C-C bond formation; the cycloadditions and ring rearrangements; the reduction of azetidin-2-ones; the miscellaneous syntheses and the important classes of compounds; the staudinger reaction; the enolate-imine condensation; the kinugasa reaction; the isocyanate cycloaddition; [3+1]-annulation; the cyclizations; and finally the heterocyclic compounds.