Synthesis of 3,3-difluoro-2-azetidinones and 2,3-dideoxy-2,2-difluoro-3-amino-sugars through the reformatsky reaction of difluoroacetate with imine

The Reformatsky reaction of iodo- or bromodifluoroacetate with imine(5) gave the corresponding 3,3-difluoro-2-azetidinone derivative(1). Reaction of 2,2-difluoroketene silyl acetal(4) with the imine(5a) or N,O-acetal derivatives(8, 9) gave the 3-amino-2,2-difluoro esters. 2,2-Difluoro analogs of 2,3-dideoxy-3-aminosugars(2) including daunosamine derivative (2a) were efficiently prepared through the reaction of 3 or 4 with N-benzylimine of 4-deoxy-L-threose acetonide(5a) and (R)-glyceraldehyde acetonide(5b).