The Synthesis of Phosphonate Ester Containing Fluorinated Vinyl Ethers

Three novel perfluorovinyl ethers containing phosphonate ester groups, diethyl 1,1,2,2,3,3,5,6,6-nonafluoro-4-oxa-5-hexenylphosphonate, (EtO)2P(O)(CF2)3OCFCF2 (1), diethyl 1,1,2,2,4,5,5-heptafluoro-3-oxa-4-pentenylphosphonate, (EtO)2P(O)(CF2)2OCFCF2 (2), and diethyl 1,1,2,2,4,5,5,7,8,8-decafluoro-4-trifluoromethyl-3,6-dioxa-7-octenylphosphonate, CF2CFOCF2CF(CF3)O(CF2)2P(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.