NICKEL-CATALYZED REACTION OF IODODIFLUOROACETATES WITH ALKENES AND ZINC - A NOVEL AND PRACTICAL ROUTE TO ALPHA,ALPHA-DIFLUORO-FUNCTIONALIZED ESTERS AND ALPHA,ALPHA,OMEGA,OMEGA-TETRAFLUORO DIESTERS

lododifluoroacetates 1a-c react with alkenes and zinc in the presence of nickel dichloride hexahydrate in THF at room temperature or 60-degrees-C to give the corresponding alpha,alpha-difluoro esters in good yields. The reaction is also applicable to alkenes containing a variety of functional groups such as trimethylsilyl, hydroxy, ketone, and ester moieties. The reaction of 1 works well with dienes; the products formed depend on the length of chain of the dienes. 1,8-Nonadiene and 1,5-hexadiene afford the alpha,alpha,omega,omega-tetrafluoro diesters, while 1,6-heptadiene gave a mixture of ethyl 2,2-difluoro-8-nonenoate (19) and the cyclopentyl-substituted alpha,alpha-difluoro ester 20. When diallyl ether was used as a substrate, only the tetrahydrofuran derivative 21 was formed. The nickel-catalyzed reaction can be suppressed by p-dinitrobenzene and hydroquinone. A single electron transfer initiated radical mechanism is proposed.