A USEFUL MAGNESIUM REAGENT FOR THE PREPARATION OF 1,1-DIFLUORO-2-HYDROXYPHOSPHONATES FROM DIETHYL BROMODIFLUOROMETHYLPHOSPHONATE VIA A METAL-HALOGEN EXCHANGE-REACTION

When (EtO)(2)P(O)CF2Br (1) is treated with isopropylmagnesium chloride in THF at low temperature it gives a magnesium species (2) which unde rgoes reactions with strong electrophiles (HCl, TMSCl, halogens, aldeh ydes and ketones). The formation of products depends strongly on the r eaction conditions. With 1.5 equivalents of 2 between -78 and 0 degree s C, a conversion of more than 90% of aldehydes and ketones into 2-hyd roxyphosphonates (7 and 8) can be achieved. These compounds (7 and 8) in the presence of base (NaH, LDA) are rearranged into 2,2-difluoroeth ylphosphates without concomitant formation of 1,1-difluoroolefines.