Harold C. Fielding

Reactions of tetrafluoroethylene oligomers. Part 1. Some pyrolytic reactions of the pentamer and hexaher and of the fluorine adducts of the tetramer and pentamer

Abstract Pyrolyses of these highly branched fluorocarbons over glass beads caused the preferential thermolyses of CC bonds where there is maximum carbon substitution. Fluorinations of perfluoro-3,4-dimethylhex-3-ene (tetramer) (I) and perfluoro-4-ethyl-3,4-dimethylhex- 2-ehe (pentamer) (II) over cobalt (III) fluoride at 230° and 145° respectively afforded the corresponding saturated fluorocarbons (III) and (IV), though II gave principally the saturated tetramer (III) at 250°. Pyrolysis of III alone at 500—520° gave perfluoro-2-methylbutane (V), whilst pyrolysis of III in the presence of bromine or toluene afforded 2-bromononafluorobutane (VI) and 2H-nonafluorobutane (VII) respectively. Pyrolysis of perfluoro-3-ethyl-3, 4-dimethylhexane (IV) alone gave a mixture of perfluoro-2-methylbutane (V), perfluoro-2-methylbut-1-ene (VIII), perfluoro-3-methylpentane (IX), perfluoro-3,3-dimethylpentane (X), and perfluoro-3,4- dimethylhexane (III). Pyrolysis of IV in the presence of bromine gave (VI) and 3-bromo-3-trifluoromethyl-decafluoropentane (XI): with toluene, pyrolysis gare VlI and 3H-3-trifluoromethyldecafluoropentane (XII). Pyrolysis of II at 500° over glass gave perfluoro-1,2,3-trimethylcyclobutene (XIII) and perfluoro-2,3-dimethylpenta-1,3(E)- and (Z)-diene (XIV) and (XV) respectively. The diene mixture (XIV and XV) was fluorinated with CoF 3 to give perfluoro-2,3-dimethylpentane (XVI) and was cyclised thermally to give the cyclobutene (XIII). Pyrolysis of perfluoro-2- (1′-ethyl-1′-methylpropyl)-3-methylpent-1-ene (XVII) (TFE hexamer major isomer) at 500° gave perfluoro-1-methyl-2-(1′-methylpropyl)cyclobut-1-ene (XVIII) and perfluoro-2-methyl-2-(1′-methylpropyl)buta-1,3-diene (XIX). Fluorination of XVIII over CoF 3 gave perfluoro-1-methyl-2- (1′-methylpropyl)cyclobutane (XX), which on co-pyrolysis with bromine gave VI. XIX on heating gave XVIII. Reaction of XVIII with ammonia in ether gave a mixture of E and Z 1′-trifluoromethyl-2-(1′-trifluoromethyl- pentafluoropropyliden-1′-yl)tetrafluorocyclobutylamine (XXI) which on diazotisation and hydrolysis afforded 2-(2′trifluoromethyl- tetrafluorocyclobut-1-en-1′-yl)-octafluorobutan-2-ol (XXII).

An isolatable α-lactone made by direct epoxidation

Epoxidation of perfluoro-[(1-ethyl-1-methylpropyl)(1-methylpropyl)]keten with sodium hypochlorite–acetonitrile afforded a high yield of perfluoro-[(1-ethyl-1-methylpropyl)(1-methylpropyl)]-ethanolide, the most stable α-lactone yet to be isolated.

Polyfluoro-1,2-epoxy alkanes and cycloalkanes. Part IV [1]. Thermal reactions of the epoxides of the pentamer and hexamer oligomers of tetrafluoroethene

Abstract Oxirans (1) and (2), derived respectively from the pentamer and hexamer oligomers of tetrafluoroethene, were pyrolysed over pyrex glass at 300–500° alone and in the presence of cyclohexene, bromine and toluene. Thus, oxiran (1), pyrolysed alone, afforded perfluoro-2-methylbut-1-ene (3), perfluoro-2,3-dimethylpent-2-ene (4) and (E) and (Z) perfluoro-2,3-hex-3-ene (TFE tetramer) (5a, 5b). Co-pyrolysis of (1) with bromine afforded (E) and (Z) 2-bromoperfluoro-3-methylpent-2-ene (6a, 6b), whilst with toluene, (E) and (Z) 2H-perfluoro-3-methylpent-2-ene (7a, 7b) were obtained: (1) with excess cyclohexene also gave (7a, 7b). The oxiran (2), on pyrolysis alone, gave only (3). In the presence of bromine, (2) gave an equimolar mixture of 1-bromoperfluoro-3-methylpentan-2-one (8) and 3-bromoperfluoro-3-methylpentane (9). Co-pyrolysis of (2) with toluene yielded (3) and 3H-perfluoro-3-methylpentane (10). Pyrolysis of (2) with cyclohexene at 175° gave perfluoro-3-methyl-2-(1-methylpropyl)pent-2-en-1-oylfluoride (11), pentafluoroethylcyclohexane (12) and perfluoro[(1-ethyl-1-methylpropyl) (1-methylpropyl)]ketne (13).

Reactions of tetrafluoroethene oligomers. Part 4. Some reactions of the major hexamer oligomer with nucleophiles based on oxygen and sulphur

Abstract The major hexamer oligomer of tetrafluoroethene [perfluoro-2-(1-ethyl-1-methylpropyl)-3-methyl-pent-1-ene] (1) reacted with sodium hydroxide under vigorous conditions to afford perfluoro-[(1-ethyl-1-methylpropyl) (1-methylpropyl)]keten (3). Reaction of (1) with methoxide ion in methanol afforded 4-methoxycarbonyl-heneicosafluoro-3,5-dimethyl-5-ethyl-hept-3-ene (5) whereas reaction with methanol In the presence of triethylamine initially afforded (5), but on further reaction yielded (E, Z)-4H-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (4). Reaction of (1) with potassium-t-butoxide in t-butanol afforded (3) whilst with water/triethylamine (4) was obtained. With ethanethiol and sodium benzylthiolate, respectively, hexamer (1) gave ethyl and benzyl [tricosafluoro-3-ethyl-3-methyl-2-(1-methylpropyl)pent-1-enyl]sulphides (6) and (7). With aqueous potassium cyanide 1-cyanotricosafluoro-3-ethyl-3-methyl-2-(1-methylpropyl)pent-1-ene (8) was obtained.

Relative reactivities of isomeric perfluoroalkenes

Abstract We have already reported on some reactions of perfluoro-3,4-dimethyl-3-hexene (1) with O-nucleophiles and the products are derived from attack on both (1) and its isomer (2), which are apparently in equilibrium in solution and in the presence of fluoride ion [1].

Reactions of tetrafluoroethene oligomers. Part 5. Some reactions of perfluoro-[(1-ethyl-1-methylpropyl)(1-methylpropyl)] keten

Abstract The title keten (1) was treated with some alcohols and amines: methanol afforded an inseparable mixture of two products, 4H-4-methoxycarbonyl-docosafluoro-3,5-dimethyl-3-ethylheptane (2) and 4-methoxycarbonyl-heneicosafluoro-3,5-dimethyl-8-ethylhept-3-ene (3). Treatment of the mixture with sodium hydroxide afforded pure (3). Reaction of (1) with benzyl alcohol yielded 4-benzyloxycarbonyl-4H-docosafluoro-3,5-dimethyl-3-ethylheptane (4) which on hydrogenation gave a mixture of 4H-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (5) and 4H-docosafluoro-3,5-dimethyl-3-ethyl-heptane-4-carboxylic acid (6). Reaction of (1) with ammonia yielded 4-carbonamido-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (7) and dimethylamine similarly afforded the N,N-dimethyl analogue (9). However, reaction of (1) with ethylamine gave an unusual cyclisation product, 1-ethyl-3H-heneicosafluoro-4-ethyl-4-methyl-3(1-ethyl-1-methylpropyl)azetan-2-one (8).

Reactions of tetrafluoroethylene oligomers. Part 2. Some reactions of 4,4,5,5,5-pentafluoro-3-pentafluoroethyl-3-trifluoromethylpentanoic acid (pentamer acid) and related compounds

The acid RfCH2CO2H (1)[Rf= CF3(C2F5)2C] derived from the tetrafluoroethylene pentamer (2) by base hydrolysis has been converted by Kolbe electrolysis into the dimer RfCH2CH2Rf(3). The salt RfCH2CO2Ag (4) with bromine afforded RfCH2Br (5) which was unreactive to nucleophiles under a variety of conditions. RfCH2COCl (6) with sodium azide under Curtius reaction conditions gave (RfCH2NH)2CO (7), whereas reaction of (6) with trimethylsilyl azide or sodium azide–18-crown-6 gave RfCH2NCO (8). RfCH2NCO and cyclohexylamine gave RfCH2NHCONHC6H11(9). Neither urea, (7) or (9), could be hydrolysed. RfCH2COCl (6) reacted with ammonia to give RfCH2CONH2(10) and with cyclohexylamine to yield RfCH2CONHC6H11(11). The amide (10) under Hofmann degradation conditions gave the urea (7). The acid (1) reacted with sodium azide in 25% oleum to yield RfCH2NH3+ HSO4–(12) which, on reaction with dilute base, gave RfCH2NH2(13). Reaction of RfCH2NH3(13) or RfCH2NH3+ HSO4–(12) with sodium nitrite afforded RfCHN2(14) as a stable liquid.

Reactions involving fluoride ion. Part 22. Dimerisation of perfluoro-2,3-dimethylbutadiene and related reactions

Reaction of perfluoro-2,3-dimethylbutadiene (1) with caesium fluoride gives two dimers, the ratios being very temperature-dependent. The structures of the dimers and mechanism of formation are proposed. A corresponding reaction but in the presence of bromine provides a good route to perfluoro-2,3-dimethylbut-2-ene. Further fluorination of the dimers of (1) occurs over cobalt trifluoride and the product may be rationalised on the basis of an intermediate radical cation.

Reactions involving fluoride ion. Part 20. Competition between isomerization and nucleophilic attack on a perfluoroalkene

Reaction of perfluoro-3,4-dimethylhex-3-ene (1) with amine gives products which arise from nucleophilic attack directly on (1) but also products derived from attack on isomers of (1), i.e. perfluoro-3,4-dimethylhex-2-ene (2) and perfluoro-3-methylene-4-methylhexane (3), promoted by fluoride ion which is generated during reaction. The products obtained depend critically on the steric requirements of the attacking amine, e.g. Et2NH gives products arising exclusively from attack on isomer (3).

Reactions involving fluoride ion. Part 16. Nucleophilic attack on a perfluorotetra-alkylethylene and a synthesis of perfluorotetramethylfuran

Reaction of perfluoro-3,4-dimethylhex-3-ene (1) with oxygen nucleophiles gives products arising from attack on (1) as well as products arising from attack on the isomer, perfluoro-3,4-dimethylhex-2-ene (4). A novel cyclisation and defluorination is described for the reaction of (1) with MeOH and Et3N, giving perfluorotetramethylfuran. Reactions of (1) with difunctional nucleophiles give cyclic products and oxidation of (1) with KMnO4 in acetone yields a diol. An unusual intramolecular nucleophilic displacement of fluoride from a perfluoroalkyl group is reported.