T. I. Filyakova

Perfluoroepoxyoxolanes in the synthesis of fluorine-containing heterocycles

Perfluoro-3,4-epoxyoxolane and 3,4-epoxy-2-trifluoromethylpentafluorooxolane readily reacted with difunctional nucleophiles via opening of the oxirane ring and subsequent heterocyclization. Their reactions with thiourea and o-phenylenediamine gave new fluorine-containing fused heterocyclic compounds, 2-amino-3a-hydroxy-4,4,6,6,6a-pentafluoro-3a,4,6,6a-tetrahydrofuro[3,4-d][1,3]thiazole and 1,1,3,3-tetrafluoro- and 1-trifluoromethyl-1,3,3-trifluoro-1,3-dihydrofuro[3,4-b]quinoxalines, respectively. The molecular and crystalline structures of the products were determined by X-ray analysis.

2,3-Epoxyperfluoro-2-methylpentane in reactions with urea and thiourea

Abstract2,3-Epoxyperfluoro-2-methylpentane reacts with thiourea in protic (methanol, 2-propanol) and aprotic (dioxane) solvents, and also with urea in acetonitrile affording unexpected products: 1-(2,2,3,3,3-pentafluoropropionyl)-2-(2,2,2-trifluoro-1-trifluoro-methylethyl)isothiourea, and 1-(2,2,3,3,3-pentafluoropropionyl)-3-(2,2,2-trifluoro-1-trifluoro-methylethyl)urea respectively that result from the rearrangement of the intermediately formed ketone in the process of the intramolecular “haloform” cleavage. At the same time in dioxane the 2,3-epoxyperfluoro-2-methylpentane reacts with urea with the formation of a heterocyclic compound, 2-amino-4-pentafluoroethyl-5,5-bis(trifluoromethyl)-4,5-dihydrooxazol-4-ol. From 1-(2,2,3,3,3-pentafluoropropionyl)-2-(2,2,2-trifluoro-1-trifluoromethylethyl)isothiourea and Cu(OAc)2 a stable fluorine-containing chelate complex was obtained.

Synthesis and structure of reaction products obtained from 1,2-epoxyperfluorobutane and bifunctional nucleophilic reagents

Abstract1,2-Epoxyperfluorobutane readily reacts with bifunctional nucleophilic reagents to provide heterocyclic compounds with a pentafluoroethyl substituent. The reaction of this epoxide with thiourea and acetone thiosemicarbazone gave rise to 2-amino-5-pentafluoroethyl-5-fluoro-4(5H)-thiazolinone and 2-isopropylidenehydrazono-5-pentafluoroethyl-5-fluoro-4-thiazolidinone respectively. The reaction of 1,2-epoxyperfluorobutane with o-phenylenediamine and 2,3-diaminonaphthalene afforded in high yields 3-pentafluoroethyl-2(1H)-quinoxalinone and 3-(pentafluoroethyl)benzo[g]-2(1H)-quinoxalinone. The molecular and crystal structure of the obtained fluorine-containing heterocycles was established by XRD analysis.

Fluoroolefin oxides. 1. A new method of synthesis of perfluorinated epoxyalkanes

Conclusions1.A new, convenient method has been developed for the epoxidation of terminal and internal perfluoroolefins by alkali and alkaline-earth hypohalites in alkaline solution in the presence of aprotic solvents.2.In the presence of nucleophilic and electrophilic catalysts the oxides of internal perfluoroolefins are isomerized to ketones.

Perfluoro(1,2-epoxycyclohexane) in the synthesis of fluorinated heterocycles

Perfluoro(1,2-epoxycyclohexane) readily reacts with bifunctional nucleophiles (urea, thiourea, and benzene-1,2-diamine) via opening of the oxirane ring and subsequent heterocyclization to give fluorinated benzimidazole, 1,3-benzothiazole, and phenazine derivatives, respectively.

Reaction with alcohols of 1-bromo(chloro)-1,2-epoxyheptafluorobutanes and 1,2-epoxyperfluorobutane. Preparation of α-bromo-, α-chloro-, and α-alkoxyhexafluorobutyric acids esters

Abstract1-Bromo(chloro)-1,2-epoxyheptafluorobutanes reacted with primary and secondary alcohols by two concurrent routes giving a mixture of esters of α-alkoxy-and α-bromo(chloro)-hexafluorobutyric acids with growing content of the latter on increasing the bulk of the nucleophilic agent. 1,2-Epoxyperfluorobutane under the same conditions was converted into α-alkoxyhexafluorobutyric acid esters. Reaction of 1-bromo-1,2-epoxyheptafluorobutane and 1,2-epoxyperfluorobutane with potassium tert-butylate in tert-butanol resulted in tert-butyl α-bromohexafluorobutyrate and heptafluorobutyrate respectively due to the forced attack of the bulky nucleophile on the terminal carbon atom of the epoxy ring.

Synthesis of perfluoro- and 2-trifluoromethylpentafluorodihydrofurans and their epoxy derivatives

Perfluorotetrahydrofuran-2-carboxylic acid was converted through a series of transformations into perfluoro-2,3-dihydrofuran and perfluoro-2,5-dihydrofuran; likewise, from (2-perfluorotetrahydrofuryl)difluoroacetic acid 2-trifluoromethylpentafluoro-2,3-dihydrofuran was obtained. Perfluoro-2,3-dihydrofuran and 2-trifluoromethylpentafluoro-2,3-dihydrofuran underwent isomerization into perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran by the action of cesium fluoride. Treatment of perfluoro-2,5-dihydrofuran with SbF5 resulted in ring opening and formation of cis-perfluoro-2-butenoyl fluoride, while 2-trifluoromethylpentafluoro-2,3-dihydrofuran was converted into 2-trifluoromethylpentafluoro-2,5-dihydrofuran under the same conditions. Perfluoro-3,4-epoxytetrahydrofuran and 2-trifluoromethyl-3,4-epoxypentafluorotetrahydrofuran containing fused oxirane and tetrahydrofuran rings were synthesized by reactions of perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran, respectively, with sodium hypochlorite.

ISOMERIZATION OF MONOHYDROPERFLUOROALKENES

Isomerization of monohydroperfluoro-1-alkenes HC(CF2)nCF=CF2 (n = 2 to 8) catalyzed by Lewis bases or acids (CsF, KHF2, and SbF5) under conditions of thermodynamic control affords equilibrium mixtures of all of the possible isomers resulting from migration of the double bond along the carbon chain. Under conditions of kinetic control, isomerization through the action of SbF5 gives ω-H-perfluoro-2-alkenes. The substantially higher proportion ofcis-isomers in the resulting monohydroperfluoroalkenes than in their perfluorinated analogs has been attributed to the effect of an intramolecular hydrogen bond.

Isomeric transformations of polyfluorobutenes caused by SbF5

ConclusionsThe 4-H- and 4-Cl-perfluoro-1-butenes when treated with SbF5 rearrange to terminal polyfluorobutenes that contain either H or Cl at the multiple bond.

Reactions of perfluoro(2,3-epoxy-2-methylpentane) with o-phenylenediamine and ethylenediamine

Perfluoro(2,3-epoxy-2-methylpentane) reacted with o-phenylenediamine and ethylenediamine via cleavage of the C-C bond to produce 2,2,3,3,3-pentafluoro-N-[2-(2,2,2-trifluoro-1-trifluoromethylethylamino)-phenyl]propanamide and 2,2,3,3,3-pentafluoro-N-[2-(2,2,2-trifluoro-1-trifluoromethylethylamino)ethyl]-propanamide, respectively. Presumably, these compounds are formed as a result of rearrangement of intermediate ketone generated by intramolecular haloform-type reaction. According to the NMR and X-ray diffraction data, 2,2,3,3,3-pentafluoro-N-[2-(2,2,2-trifluoro-1-trifluoromethylethylamino)phenyl]propanamide in crystal exists as Z conformer with respect to the amide C-N bond.