A NOVEL AND PRACTICAL PREPARATION OF ALPHA,ALPHA-DIFLUORO FUNCTIONALIZED PHOSPHONATES FROM IODODIFLUOROMETHYLPHOSPHONATE

The addition reaction of iododifluoromethylphosphonate 1 with alkenes is catalyzed by tetrakis(triphenylphosphine)palladium or copper metal under mild conditions. A variety of functional groups, including alkyl, trimethylsilyl, hydroxy, epoxy, acetoxy, ketone, and ester, in the alkenes could be tolerated under the reaction conditions. Reaction of 2 equiv of 1 with dienes gives the corresponding bisphosphonates. Although the palladium complex fails to induce addition of 1 to cyclohexene, the addition reaction proceeds readily with copper at 85-degrees-C. With diallyl ether, a tetrahydrofuran derivative is obtained. Electron scavenger and radical inhibitors suppressed the addition reaction completely. A single electron transfer initiated radical mechanism is proposed. Treatment of the adducts with zinc in the presence of nickel chloride in moist THF at room temperature provides the corresponding alpha,alpha-difluoro-functionalized phosphonates in good yields.