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In the presence of 1.2−1.5 equiv of potassium fluoride, a variety of (E)- and (Z)-(2-substituted-1,2-difluoroethenyl)silanes reacted with tributyltin chloride in DMF at room temperature to 80 °C to afford the corresponding stannanes in good yields with overall retention of configuration. These stannanes are useful intermediates for the introduction of the (E)- and (Z)-1,2-difluoroethylene unit into organic molecules. Under similar reaction conditions, only catalytic potassium fluoride (5−10%) was needed for these conversions when tributyltin chloride was replaced by tributyltin oxide. The mechanism and scope of this transformation is discussed.

Three novel perfluorovinyl ethers containing phosphonate ester groups, diethyl 1,1,2,2,3,3,5,6,6-nonafluoro-4-oxa-5-hexenylphosphonate, (EtO)(2)P(O)(CF(2))(3)OCF=CF(2) (1), diethyl 1,1,2,2,4,5,5-heptafluoro-3-oxa-4-pentenylphosphonate, (EtO)(2)P(O)(CF(2))(2)OCF=CF(2) (2), and diethyl 1,1,2,2,4,5,5,7,8,8-decafluoro-4-trifluoromethyl-3,6-dioxa-7-octenylphosphonate, CF(2)=CFOCF(2)CF(CF(3))O(CF(2))(2)P(O)(OEt)(2) (3), have been synthesized. Perfluorovinyl ethers 1 and 2 were synthesized from methyl 4-trifluoroethenoxy-2,2,3,3,4,4-hexafluorobutanoate and methyl 3-trifluoroethenoxy-2,2,3,3-tetrafluoropropanoate, respectively, while perfluorovinyl ether 3 was synthesized either from 5-trifluoroethenoxy-4-trifluoromethyl-3-oxa-1,1,2,2,4,5,5-heptafluoropentylsulfonyl fluoride or methyl 6-trifluoroethenoxy-5-trifluoromethyl-4-oxa-2,2,3,3,5,6,6-heptafluorohexanoate. The carboxylate esters were converted to the corresponding fluoroalkyl iodides via a free-radical iododecarboxylation. The sulfonyl fluoride was converted to its corresponding fluoroalkyl iodide via iododesulfination. The intermediate iodides were found to be useful precursors for the incorporation of the phosphonic ester groups via a photoreaction with tetraethyl pyrophosphite to produce diethyl fluorophosphonites. The diethyl fluorophosphonites were oxidized to the desired phosphonates, 1, 2, and 3, utilizing hydrogen peroxide as the oxidant. Moderate to good overall yields of perfluorovinyl ethers 1-3 have been achieved.

Title cumulenes 2a and 2b were prepared by reaction of CF3(Ph)C=C(Br)ZnX [X = Br, CF3(Ph)C=CBr-] 1 with CuBr, or by oxidative coupling of 1 with FeCI3 to form 2a,b and [CF3(Ph)C=CBr-I2 3, which can be dehalogenated with zinc to afford 2a,b; the cumulene isomers are readily separated by silica-gel chromatography, and may be prepared in good yield on a multi-gram scale.

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