Fluorocarbon derivatives of nitrogen. Part 10. Preparation of heptafluoro- and 1-chlorohexafluoro-2-nitrosopropane,and conversion on the latter to chloropentafluoroacetone oxime

Details are given for the preparation of heptafluoro-2-nitrosopropane and 1-chlorohexafluoro-2-nitrosopropane $\text{via}$ the routes CF₃CFCF₂ → [with CsFR_FCO₂Ag (R_F = CF₃, nC₃F₇)] (CF₃)₂CFAg → (with NOCl) (CF₃)₂CFNO and CF₃CFCF₂ → (with CsClNOCl) CF₃(CF₂Cl)CFNO, respectively, and for conversion of the latter nitroso-compound to chloropentafluoroacetone oxime $\text{via}$ reduction with aqueous potassium hydrogen sulphite.     

Formation and Stability of Difluoromethylene Phospho-Raiies,R3P=CF2

Abstract

Carbonyl compounds react with CBr₂F₂ in the presence of phosphanes, RP (R = Ph, NR;), and metals (M = Zn, Cd, Pb) forming geminal difluoroolefins (eq. 1)¹.

R′CHO + CBr₂F₂ + R₃P + M → R′CH=CF₂ + MBr₂ + R₃PO (1)

Without any doubt this reaction has to occur via the intermediate formation of difluoromethylene phosphoranes, which then undergo the Wittig reaction with carbonyl compounds (eq. 2). R₃P=CF₂ + R′CHO → R₃PO + R′CH=CF₂ (2).     

Long path-FTIR studies of some atmospheric reactions involving CF3OO and CF3O radicals

In attempts to obtain kinetic and mechanistic data required for an assessment of atmospheric fate of alternative halocarbons containing a CF₃ group, reactions of the key free radical intermediates CF₃OO and CF₃O with several atmospheric compounds (i.e., NO, NO₂, alkanes and alkenes) have been studied at 297 ± 2 K in 700 torr of air. Experiments employed the long path-FTIR spectroscopic method for product analysis and the visible (400 nm) photolysis of CF₃NO → CF₃ + NO as a source for the precursor radical CF₃. Numerous labile and stable F-containing molecular products have been characterized based on kinetic and spectroscopic data obtained at sufficiently short photolysis time (≤1 min) to minimize heterogeneous decay on the reactor walls. Major new findings have been made for the reactions involving CF₃O radicals. The behavior of CF₃O radicals has been shown to be markedly different from that of CH₃O radicals, i.e., (1) O₂-reaction: no evidence for the F-atom transfer reaction CF₃O + O₂ → CF₂ O + FOO; (2) NO-reaction: addition reaction CH₃O + NO (+M) → CH₃ONO (+M), but F-transfer reaction CF₃O + NO → CF₂O + FNO; (3) NO₂-reaction: addition reaction for both radicals, but F-transfer reaction CF₃ + NO₂ → CF₂O + FNO₂ to a minor extent; (4) alkane-reaction: much faster H-abstraction by CF₃O, comparable to HO; (5) alkene-reaction: much faster addition reaction of CF₃O, comparable to HO. These results are summarized in this paper.     

Kinetics of the reaction F + 1,2-dibromo-1,1,2-trifluoroethane

The title reaction was studied in a standard flow system with F atoms produced by RF discharge in F₂-He mixture. Analysis was by gas chromatography using electron capture detection. There were two major products, identified as CF₂BrCF₂H and CF₂BrCF₂Br, plus presumably HF which was not detectable. The overall rate of disappearance of reactant was found to be of mixed one and one-half order, indicating a complex reaction. A mechanism is proposed comprising six steps and involving two radical species CF₂Br?FBr (R₁) and CF₂Br?F₂. The 300 K rate constant for the initial step F + reactant → HF + R₁ is evaluated to be 2.2 × 10^?13 cm³/molec·s, which fits in with rates of other saturated hydrocarbon reactants containing one hydrogen atom, thus supporting the view that in this class of reactants the rates of reactions of the type F + saturated hydrocarbon depend mainly on the number of hydrogen atoms in the reactant.     

Relative rate constants for reactions of HFC 152a, 143, 143a, 134a,and HCFC 124 with F or Cl atoms and for CF2CH3, CF2HCH2, and CF3CFH radicals with F2, Cl2, and O2

Relative rate experiments using UV photolysis of F₂ or Cl₂ have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F₂ present, dark reactions are, also, observed which are attributed to thermal dissociation of the F₂ to form F atoms. At 296 K, the rate of reaction (1a) [CF₂HCH₃ + F → CF₂CH₃ + HF] relative to (1b) [CF₂HCH₃ + F → CF₂HCH₂ + HF] is k_1a/k_1b = 0.73 (±0.13) and is independent of T (= 262–348 K). At 296 K, the ratio of reaction (2a) [CF₂HCH₂F + F → products] to that of (k_1a + k_1b) is (k_1a + k_1b)/k_2a = 2.7 (±0.4), and for reaction (2b) [CF₃CH₃ + F → products] (k_1a + k_1b)/k_2b = 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF₃CFH₂ + Cl → products] relative to reaction (4) [CF₃CFClH + Cl → products] is k₃/k₄(±10%) = 1.55 exp(?300 K/T). For the alkyl radicals formed from HFC 152a (CF₂HCH₂ and CF₂CH₃) and from HFC 134a (CF₃CFH), rate constants for the reactions with F₂ and Cl₂ were measured relative to their reactions with O₂. The rate constant of reaction (5cl) [CF₂CH₃ + Cl₂ → CF₂ClCH₃ + Cl] relative to (5o) [CF₂CH₃ + O₂ → CF₂(O₂)CH₃] is k_5cl/k_5o(±15%) = 0.3 exp(200 K/T). For reaction (5f) [CF₂CH₃ + F₂ → CF₃CH₃ + F], k_5f/k_5o(±35%) = 0.23. The ratio for reaction (6f) [CF₂HCH₂ + F₂ → CF₂HCH₂F + F] relative to (6o) [CF₂HCH₂ + O₂ → CF₂HCH₂O₂] is k_6f/k_6o(±40%) = 1.23 exp(?730 K/T). The rate constant ratio for reaction (8cl) [CF₃CFH + Cl₂ → CF₃CFClH + Cl] relative to reaction (8o) [CF₃CFH + O₂ → CF₃CFHO₂] is k_8cl/k_8o(±18%) = 0.16 exp(?940 K/T). For reaction (8f) [CF₃CFH + F₂ → CF₃CF₂H + F], k_8f/k_8o(±35%) = 0.6 exp(?860 K/T). © 1993 John Wiley & Sons, Inc.     

Solvents effects in reactions between perfluoroalkyliodides and cadmium

The interaction between perfluoroorgano iodides (R_fI where R_f = F(CF₃)₂C(CF₂CF₂)₃, n-C₆F₁₃,n-C₈F₁₇, F(CF₃)₂COCF₂CF₂,F(CF₃)₂CO(CF₂CF₂)₄ andC₂H₅OC(O)(CF₂CF₂) with cadmium in an acetonitrilesolvent media produces primarily the coupled products (R_fR_f,72–90% yield) in addition to minor quantities of the reduction products (R_fH). On the other hand ICF₂CF₂I and C1CF₂CFC1I, by a 1,2-dehalogenation reaction, form the olefins CF₂ = CF₂ and CF₂ = CFC1, respectively, as the principal products. The interaction of R_fI compounds with cadmium in other solvent media, e.g. diethyl ether. tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and bis(2-methoxyethyl)ether(diglyme) were examined and found to produce a different ratio of R_fR_f and R_fH products. {ft*}Present address: Fluidics Inc., P.O.Box 1886, Dayton, OH 45429 U.S.A.     

A Convenient Route to Tetraalkylammonium Perfluoroalkoxides from Hydrofluoroethers

Hydrofluoroethers are shown to alkylate tertiary amines readily under solvent‐free conditions, affording valuable tetraalkylammonium perfluoroalkoxides bearing α‐fluorines. The reaction of R_FCF₂? OCH₃ (R_F=CF₂CF₃, CF₂CF₂CF₃, and CF(CF₃)₂) with NR¹R²R³ produces twenty new α‐perfluoroalkoxides, [(CH₃)NR¹R²R³][R_FCF₂O] under mild conditions. These α‐perfluoroalkoxides are easy to handle, thermally stable, and can be used for the perfluoroalkoxylation of benzyl bromides.     

Advances in Trifluoromethylating Phosphorus Compounds

Abstract

The System CF₃I/Me₃P is re-investigated and Me₂PCF₃, Me₄P⁺γ, (CF₃)₂PMe₃, Me₃PI₂, [Me₃(CF₃)P]⁺γ are found as products. Using CF₃Br/P(NEt₂)₃ the phosphines R¹ ₂PCF₃ and R¹P(CF₃)₂ (e.g. R¹ = Me, iPr, NEt₂) can be obtained which are precursors either for phosphoranes (e.g. 1,2λ⁵σ⁵-oxaphosphetanes) or phosphonium salts (e.g. [R¹ ₂(Me)PCF₃]⁺X^? or [R¹(Me)P(CF₃)₂X^?]. The latter are deprotonated to furnish methylene phosphoranes R¹ ₂(CH₂=)PCF₃ or R¹(CH₂=)P(CF₃)₂, reactive synthons. From CF₃Br/P(NEt₂)₃/P(OPh)₃ the phosphine P(CF₃)₃ is available, which turned out to be a potent electrophile. Amido phospites ROP(NEt₂)₂ and halides R²X (R²=CCl₂CF₃, X=Cl; R²=CF=CFCF₃, X=F; R²=C₆F₅, X=Br, I; R²=C(CF₃)₃, X=Br; R²=SCF₃, X=CF₃) undergo an ARBUZOV reaction.     

Mechanism and kinetics of the reaction of F with trivalent phosphorus iodide using electron spin resonance detection

The reaction of iodobistrifluoromethylphosphine, P(CF₃)₂I, with atomic fluorine was studied by fast-flow ESR methods. The initial stage of the reaction is the abstraction of I by F, to form IF with a bimolecular rate constant of (1.0 ± 0.3) × 10¹⁴ cm³ mol^?1 s^?1 at 297 K. In the presence of excess F, stepwise addition to the phosphorous occurs. In the presence of excess P(CF₃)₂I, the reaction P(CF₃)₂ + IF → P (CF₃)₂F + I appears to take place. This reaction rate is slow relative to P(CF₃)₂ + F → P(CF₃)₂F.     

Fluoro-olefin chemistry Part 20 [1]. Reaction of hexafluoropropene with alcohols

Reaction of hexafluoropropene (HFP) with a series of alcohols under thermal, photochemical or peroxide-initiated conditions affords the 1:1 adducts CF₃CHFCF₂CR¹R²OH (R¹ = H, R² = H, Me, Prⁿ or CF₃; R¹ = Me, R² = Me or Et) in high yield via a radical chain mechanism. Adduct are not formed with the alcohols (CF₃)₂CHOH and CF₃CHFCF₂CH₂OH. Other 1:1 adducts of structure CHF₂CF(CF₃)CH₂OH and CH₃(C₂H₃CF₂CHFCF₃)CH₂OH are formed as minor products in the methanol and $\text{n}$-butanol reactions, respectively.     

Nitroxide chemistry. Part XIV [1]. Reactions of trifluoromethyl 2,3-dimethylbut-3-en-2-yl and trifluoromethyl 2,3-dimethylbut-2-yl nitroxides

The nitroxide CF₃N(?)CMe₂CMeCH₂ abstracts the aldehydic hydrogen from benzaldehyde, yielding the benzoyl compound PhCO₂N(CF₃)CMe₂CMeCH₂ (82%), the benzylic hydrogen from cumene, yielding PhCMe₂ON(CF₃)CMe₂CMeCH₂ (80%), and the methylene group hydrogen from fluorene, oxidises benzoin to benzil, and hydroquinol to quinone, attacks the Si'&'2.sbnd;H bond of trimethylsilane, and adds to tetrafluoroethylene to give the compound R¹N(CF₃)OCF₂CF₂ON(CF₃)R¹ (R¹ = CMe₂CMeCH₂, 97%), and to hexafluoropropene to give the 2:1-adduct.In a similar manner, the nitroxide CF₃N(?)CMe₂CHMe₂ adds to tetrafluoroethylene to give the compound R²N(CF₃)OCF₂CF₂ON(CF₃)R² (R² = CMe₂CHMe₂, 75%) and to hexafluoropropene to give a similar adduct (71%), and abstracts a benzylic hydrogen from toluene.     

Zur Kenntnis der Sulfensäurefluoride CF3SF und CF2ClSF sowie deren Dimeren

The Sulfenic Fluorides CF₃SF and CF₂CISF and their Dimers The reactions of R_fSCl (R_f = CF₃, CF₂Cl) with HgF₂ and AgF give R_fSF and the dimer product R_fSF₂SR_f in high yield and various ratios, in contrast, activated KF leads only to R_fSF in low yield. A complex of transition metal and sulfenic halide as an intermediate step is discussed for the dimerisation. As liquid CF₃SF₂SCF₃ disproportionates into CF₃SF₃ and CF₃SSCF₃ and the hydrolysis of CF₃SF₂SCF₃ gives the stable compound CF₃S(O)SCF₃ · PF₃ reacts with R_fSF as well as with R_fSF₂SR_f to R_fSPF₄. The products of the spontaneous decomposition of CF₂ClSF were investigated. I.r., n.m.r., and mass spectra are reported and discussed. It was possible to carry out vapour pressure measurements of CF₂ClSF.     

EPR kinetic study of the reactions of CF3Br with H atoms and OH radicals

Reactions of CF₃Br with H atoms and OH radicals have been studied at room temperature at 1–2 torr pressures in a discharge flow reactor coupled to an EPR spectrometer. The rate constant of the reaction H + CF₃Br → CF₃ + HBr (1) was found to be k₁ = (3.27 ± 0.34) × 10^?14 cm³/molec·sec. For the reaction of OH with CF₃Br (8) an upper limit of 1 × 10^?15 cm³/molec·sec was determined for k₈. When H atoms were in excess compared to NO₂, used to produce OH radicals, a noticeable reactivity of OH was observed as a result of the reaction OH + HBr → H₂O + Br, HBr being produced from reaction (1).     

Thermisch beständige Trialkyl-2,2,2-trifluor-1-(trifluormethyl)-ethoxy-phosphonium Iodide

Thermally Stable Trialkyl-2,2,2-trifluoro-1-(trifluoromethyl)-ethoxyphosphonium Iodides The phosphinites R¹R²POCH(CF₃)₂ (R¹ = R² = Me, tBu; R¹ = Me, R² = tBu) react with methyl iodide to give the thermally very stable phosphonium iodides [R¹R²MePOCH(CF₃)₂]⁺I^?. In the case of tBu₂POCH(CF₃)₂ a sublimable 1:1 adduct is formed with boron trichloride.     

Nitroxide chemistry. Part XIX. Reaction of bistrifluoromethyl nitroxide with diphenylketene and related compounds (Ph2CHCOX,X  OH,Cl, NH2)

The following reactions have been accomplished: 2(CF₃)₂NO· + Ph₂CCO → Ph₂C[ON(CF₃)₂]CO₂N(CF₃)₂ → (on hydrolysis) Ph₂C[ON(CF₃)₂]CO₂H; 2 (CF₃)₂NO· + Ph₂CHCOX → (CF₃)₂NOH + Ph₂C[ON(CF₃)₂]COX (X  OH, Cl,NH₂).     

Reactions of mesomeric fluorocarbanions with acid anhydrides. Transformation of trifluoromethyl groups into fluorocarbonyl and perfluoroacyl groups

It was found that the reaction of mesomeric fluorocarbanions of the CF₃$\text{C}\text{θ}$XCOY type with benzoic anhydride leads to the loss of benzoyl fluoride and the formation of mesomeric carbanions of the FCO$\text{C}\text{θ}$XCOY type. In a similar reaction with perfluorocarboxylic acid anhydrides, besides a CF₃→COF transformation, further change of COF into COR_F is observed, leading to the formation of salts containing mesomeric anions of the R_FCO$\text{C}\text{θ}$XCOY type, which, upon acidification, give 1,1- -bis(perfluoroacyl)-2,2,2-trifluoroethanes CF₃CH(COR_F)₂ , tris- (perfluoroacyl)methanes (R_FCO)₃CH and bis(trifluoroacetyl)- acetic ester (CF₃CO)₂CHCOOMe. It has been shown that perfluoroalkyl groups in β-diketones and β,β′-triketones may hinder enolization despite their electron-attracting effect.     

Mono and Bisphosphonates from Perfluoro Olefins and Polyfunctional Fluoro Ketones. Syntheses,Molecular Structure and Derivatives

Perfluoroalkenyl phosphonates were formed along with Me₃SiF using CF₃CF=CF₂, CF₃CH=CF₂, F₅SCF=CF₂ or F₅SCH=CF₂ and silylated phosphites, (R¹O)₂POSiMe₃ (R¹=Et, SiMe₃). This straightforward method could be extended to perfluorobutadienes CF₂=C(R^F)C(R^F)=CF₂ (R^F F=F, CF₃). The formation of CF₃C(=O)P(=O)(OSiMe₃)₂ and further reactions to yield bisphosphonates will be described. Acetylphosphonates, R²C(=O)P(=O)(OSiMe₃)₂ (R²=CH₃, CF₃) reacted with the ketimine, CH₃C(=NiPr)Ph to give α-hydroxy-γ-imino phosphonates. Trifluoroacetylphenol and 2,6-bis(trifluoracetyl)-4-methyl-phenol have been proven to be versatile precursors for α-and γ-hydroxy phosphonates. Intermediates in these reactions were found to be cyclic λ⁵σ⁵P species.     

Synthesis and reactions of fluorinated iminium salts

Different methods for the preparation of fluorinated iminium salts RR¹CNR²R³⁺MF₆^? (R=R¹=F ; R²=R³=CH₃, C₂H₅ M=As, Sb 4a ? c R=H, R¹=F; R²=R³=CH₃ M=As, Sb 5a, b R=R¹=CF₃; R²=H, R³=CH₃ M=Sb 12 R=R¹=CF₃; R²=R³=CH₃ M=As 14) are reported, the spectroscopic properties (IR, NMR) of the cations of these salts are briefly discussed. By F^?-addition to these salts, $\text{e.g.}$ to 16, perfluoroalkyl-bis(alkyl)-amines ($\text{e.g.}$ (CF₃)₂CFN(CH₃)₂ 15) can be prepared; from the methylation of CF₃NCF₂ bis(trifluoromethyl) methylamine (CF₃)₂NCH₃ (11) was obtained.     

Synthesis of 1-(2-polyfluoroacylaminophenyl)-3-polyfluoroalkylpropane-1,3-diones and 2-polyfluoroalkyl-4-quinolones

The condensation of 2-aminoacetophenone with R^FCO₂Et (R^F = CF₃, CF₂H, CF₂CF₂H) in the presence of LiH in THF or Bu^tOK in Bu^tOH affords either 2-polyfluoroalkyl-4-quinolones or 1-(2-polyfluoroacylaminophenyl)-3-polyfluoroalkylpropane-1,3-diones, depending on the ratio of the initial reactants. The latter are hydrolyzed in an acidic medium to produce 2-polyfluoroalkyl-4-quinolones. N-Methyl-2-trifluoromethyl-4-quinolone was synthesized from 2-aminoacetophenone, CF₃CO₂Et, and MeI in the presence of Bu^tOK.     

1,1,1,4,5,5,5-Heptafluoro-4-(trifluoromethyl)-2,3-pentanedione,a potent reagent for the synthesis of cyclic λ5σ5 phosphoranes

1,1,1,4,5,5,5-Heptafluoro-4-(trifluoromethyl)-2,3-pentanedione reacted with λ³σ³-phosphorus compounds, PR¹R²R³ (R¹ = CF₃, R² = R³ = Me, iPr, NEt₂; R¹ = NCO, R² = R³ = OMe, OEt, R²−R³ = OCH₂CH₂O, OCMe₂CMe₂O; R¹ = OSiMe₃, R² = R³ = OEt; R¹ = NEt₂, R² = R³ = OCH₂CF₃; R¹ = R² = Et₂N, R³ = OCH₂CF₃, OCH(CF₃)₂, OCH₂Ph, OC₆F₅) to give new 1,3,2λ⁵σ⁵-dioxaphospholenes. The first λ⁵σ⁵ phosphoranes with an OCN group bonded to phosphorus were obtained. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:109–113, 1998