Hydroxylation of the enolates of several 3-alkylideneazetidin-2-ones with MoOPH leads to the formation of 3-hydroxy-3-alkenylazetidin-2-ones in fair to good yields. The products were formed with trans stereochemistry in the alkenyl moiety and a presumed trans relationship between the hydroxyl substituent and a 4-substituent. Hydrogenation leads to 3-alkyl-3-hydroxy-azetidin-2-ones. The prerequisite 3-alkylideneazetidin-2-ones were formed from 3-trimethylsilylazetidin-2-ones and aldehydes via a Peterson olefin synthesis.