Reduction process for the preparation of 4-unsubstituted azetidin-2-ones

Novel process for the preparation of azetidin-2-ones of the formula wherein R1 and R2 independently from each other are hydrogen, or an organic group linked to the ring carbon via a carbon atom, a nitrogen atom or an oxygen atom, characterized in that a corresponding 4-acyloxyazetidin-2-one, which is substituted by a group -O-CO-R3 at the 4-position, wherein R3 is hydrogen or an organic radical stable at the reaction conditions, is reacted with a complex metal hydride comprising reactive hydride ions, such as, lithium borohydride, sodium borohydride, potassium borohydride, zinc borohydride or tetraorganoammonium borohydride.