A new method for the carbon-extension reactions of azetidin-2-ones at the 4-position

High yields of 4-alkyl-, 4-allyl-, 4-vinyl-, or 4-ethynyl-azetidin-2-ones are obtained by treating 4-sulphonylazetidin-2-ones with either lithium organocuprates or Grignard reagents, but yields from 4-acetoxyazetidin-2-one with Grignard reagents are low.