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.     

Intramolecular cyclization of nerol and the related (z)-allylic alcohols by means of TiCl4-PhNHMe complex. Synthesis of nezukone

Nerol is cyclized to terpinyl chloride or bromide in the presence of TiX₄-PhNHMe (1:1) complex in dichloromethane at ?23 °C, while cyclization of ($\text{Z}$)-allylic alcohols CH₂=CR-CH₂CH₂CMe=CHCH₂OH (R = H, Me, Cl) produces seven-membered ring products in fair yields.     

Reaktionen von metall-koordiniertem kohlenmonoxid mit yliden: XVII. Darstellung eines molybdän- und wolframkomplexes mit η3-gebundenem trimethylsiloxybutenon-liganden durch silylierung der phosphonium-metall-enolat-vorstufe

The reaction of the phosphonium metallates Me₄P[C₅R₅(CO)(Me₃P)$\text{MC(O)=CHC(O}$)R′] (M = W, R = H, R′ = Et (1a); M = Mo, R = Me, R′ = Me (1b)) with the silylating reagent Me₃SiOSO₂CF₃ yields the neutral complexes C₅R₅(CO)(Me₃P)$\text{MC(OSiMe}{}_3\text{)=CHC(O}$)R (2a, 2b) bearing a chelating O(2), C(4)-trimethylsiloxybutenone ligand. The structure of the new compounds is established by the IR, ¹H and ³¹P NMR spectra.     

REACTIONS OF A PHOSPHORANIMINE ANION WITH SOME ORGANIC ELECTROPHILES

Abstract

The reactions of a variety of electrophiles with the N-silyl-P-trifluoroethoxyphosphoranimine anion Me₃Sin°P(Me)(OCH₂CF₃)CH^? ₂ (1a), prepared by the deprotonation of the dimethyl precursor Me₃SiN[dbnd]P(OCH₂CF₃)Me₂ (1) with n-BuLi in Et₂O at-78°C, were studied. Thus, treatment of 1a with alkyl halides, ethyl chloroformate, or bromine afforded the new N-silylphosphoranimine derivatives Me₃SiN[dbnd]P(Me)(OCH₂CF₃)CH₂R [2: R = Me, 3: R = CH₂Ph, 4: R = CH[sbnd]CH₂, 5: R = C(O)OEt, and 6: R = Br]. In another series, when 1a was allowed to react with various carbonyl compounds, 1,2-addition of the anion to the carbonyl group was observed. Quenching with Me₃SiCl gave the O-silylated products Me₃SiN[dbnd]P(Me)(OCH₂CF₃)CH₂°C(OSiMe₃)R¹R² [7: R ¹ = R ² = Me; 8: R ¹ = Me, R ² = Ph; 9: R¹ = Me, R ² = CH[sbnd]CH₂; and 10: R ¹ = H, R ² = Ph]. Compounds 2–10 were obtained as distillable, thermally stable liquids and were characterized by NMR spectroscopy (¹H, ¹³C, and ³¹P) and elemental analysis.     

Synthesis of Polyfluorinated Ethers

Procedures for preparing polyfluorinated ethers H(CF₂CF₂) _n CH₂OR by alkylation of the corresponding telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1–3) with alkyl halides and alkyl tosylates were examined.     

The dynamics of formation of vibrationally excited HF in reactions of O (21 D2) atoms with partially fluorinated alkanes

The nascent vibrational energy distributions of the HF? formed in the reactions of a series of partially fluorinated alkanes (R_FH; R_F = CH₂F, CHF₂, CF₃, C₂F₅, C₃F₇, and C₇F₁₅) with electronically excited oxygen atoms O(2¹D₂) have been determined by measuring the appearance times of stimulated emissions from various vibration–rotation transitions in a grating-tuned optical cavity. The vibrational energy contents of the HF formed in these reactions were found to be considerably greater than statistically expected. These reactions are believed to occur via vibrationally excited short-lived α;-fluorinated alcohols (R_FOH?), formed by insertion of the O(2¹D₂) atoms into C? H bonds. The observation of nonstatistical energy partitioning in the above reactions is in clear contrast to the result obtained from the O(2¹D₂) + CF₃CH₃ reaction that produces the β-fluorinated alcohol CF₃CH₂OH, from which the HF product carries a near statistical vibrational energy distribution. A mechanism for HF? formation in these very exothermic reactions is presented.     

Reactions of 2,2-bis(trifluoromethyl)oxirane with alcohols under phase transfer catalysis

It was demonstrated that the reaction of 2,2-bis(trifluoromethyl)oxirane (1) with variety of alcohols could be successfully carried out under phase transfer catalysis conditions using sodium or potassium hydroxide as a base. For example, reaction of CH₃OH, C₂H₅OCH₂CH₂OH, HOCH₂CH₂OH with one or two moles of 1 in the presence of the catalyst [(C₄H₉)₄N⁺HSO₄⁻] gives the corresponding tertiary alcohols R[OCH₂C(CF₃)₂OH]_n (n=1 or 2) in 43-53% yield, along with some O[CH₂C(CF₃)₂OH]₂. Benzyl alcohol and phenol under similar conditions are less active, producing in the reaction with 1 the corresponding adducts ArOCH₂C(CF₃)₂OH in 31-35% yield. Fluorinated alcohols, such as CF₃CH₂OH, ClCF₂CH₂OH, HCF₂CF₂CH₂OH have much higher reactivity towards 1 giving ring opening products in 82-97% yield. Even in the reaction of hindered hexafluoro-iso-propanol the corresponding adduct was isolated in 43% yield. Surprisingly, the reaction of iso-propanol and epoxide 1, results in the formation of O[CH₂C(CF₃)₂OH]₂ as a major product, isolated in 56% yield. Possible mechanism for the formation of the last product was proposed.     

Polymerizations of ethylenic monomers initiated by superacids—II: Complexation of some trifluoromethanesulphonates by their conjugate acid

Ionic trifluoromethanesulphonates (triflates) are strongly solvated with their conjugate acid in dichloromethane (Ph₃C⁺, n-Bu₄N⁺, Ag⁺) and acetonitrile (Na⁺, Ag⁺). A ¹H and ¹⁹F NMR study of the chemical shifts of various acid-salt mixtures show that in CH₂Cl₂ three homoconjugates A^? · HA, A^?. (HA)₂ and A^?(HA)₃ were formed with large formation constants whereas in acctonitrile only the 1:1 homoconjugate was formed with an equilibrium constant K₁ ～ 4 1 · M^?1. This result explains why the protonation by CF₃SO₃H of non-polymerizable olefins such as 1,1-diphenylethylene and 3-phenylindene is always incomplete ($\text{1}\text{3}$ and $\text{1}\text{2}$ respectively) in CH₂Cl₂. Conditions in which covalent triflates could be obtained have been investigated. As a consequence of homoconjugation, reaction of Ph₃COH with triflic anhydride led to Ph₃C⁺ CF₃SO^?₃ HOSO₂CF₃. Other tertiary alcohols were dehydrated by triflic anhydride and led to ethylenic compounds (1,1-diphenylethanol) or ethers (2-phenyl 2-propanol). Esters were only observed in the case of benzyltriflate (at ?20°) and in the case of 1-phenylethyltriflate which is a model of polystyryltriflate (stable at room temperature).     

Reactions of F-propene and its dimer with sodium dialkyldithiocarbamate

Sodium dialkyldithiocarbamates readily attacked $\text{F}$-propene to give S-(1,1,2,3,3,3-hexafluoropropyl)-N,N-dialkyldithiocarbamates, CF₃CHFCF₂SC(S)-NR₂, and $\text{Z}$ and $\text{E}$-S-(1,2,3,3,3-pentafluoropropenyl)-N,N-dialkyldithiocarbamates, CF₃CFCFSC(S)NR₂. The pyrolysis of the former compound quantitatively gave the dialkylthiocarbamoyl fluorine, R₂NC(S)F, while the latter compound and sodium tetraphenylborate formed the corresponding 1,3-dithiolan-2-ylium tetraphenylborate. $\text{F}$-2-Methyl-2-pentene also reacted with sodium dialkyldithiocarbamate to give (CF₃)₂CHC[SC(S)NR₂]CFCF₃. The mechanism of this reaction is supposed to involve a 1,4-RSF-elimination.     

Double-shift rearrangements of secondary ferrocenylcarbonium ions

In CF₃CO₂H solution, secondary ferrocenylcarbonium ions (Fc$\text{C}\text{+}$HCR¹R²R³) undergo a quantitative double-shift rearrangement to generate isomeric tertiary carbonium ions (Fc$\text{C}\text{+}$R¹CHR²R³).     

Glycosylidene Carbenes. Part 6. Synthesis of alkyl and fluoroalkyl glycosides

The syntheses of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolytic conditions are described. Yields and diastereoselectivities depend upon the pK_HA values of the alcohols, the solvent, and the reaction temperature. The glycosidation of weakly acidic alcohols (MeOH, EtOH, i-PrOH, and t-BuOH, 1 equiv. each) in CH₂Cl₂ at room temperature leads to the glycosides 2–5 in yields between 60 and 34% (Scheme 1 and Table 1). At ?70 to ?60°, yields are markedly higher. In CH₂Cl₂, diastereoselectivities are very low. In THF, at ?70 to ?60°, however, glycosidation of i-PrOH leads to α-D -/β-D - 4 in a ratio of 8:92. More strongly acidic alcohols, such as CF₃CH₂OH, (CF₃)₂ CHOH, and (CF₃)₂C(Me)OH, and the highly fluorinated long-chain alcohols CF₃(CF₂)₅(CH₂)₂OH ( 11 ) and CHF₂(CF₂)₉CH₂OH ( 13 ) react (CH₂Cl₂, r.t.) in yields between 73 and 85% and lead mainly to the β-D -glucosides β-D - 6 to β-D - 8 , β-D - 12 , and β-D - 14 (d.e. 14–68%). Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2-dimetoxyethane, or THF are used, as examined for the glycosidation of (CF₃)₂C(Me)OH, yielding (1,2-dimethoxyethane, 25°) 80% of α-D -/ β-D - 8 in a ratio of 2:98 (d.e. 96%; Table 4). In EtCN, (CF₃)₂C(Me)OH yields up to 55% of the imidate 10 . Glycosidation of di-O-isopropylideneglucose 15 leads to 16 (CH₂Cl₂, r.t.; 65%, α-D / β-D = 33:67). That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10 , derived from the attack of (CF₃)₂MeCO^? on an intermediate nitrilium ion (Scheme 4), and for weakly acidic alcohols, by the formation of α-D - 9 and β-D - 9 , derived by attack of i-PrO^? on intermediate tetrahydrofuranylium ions. A working hypothesis is presented (Scheme 3). The diastereoselectivities are rationalized on the basis of a protonation in the σ plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnO? C(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO^? in the π plane of the (solvated) oxonium ion.     

Micellar alkylation: a methylating surfactant

Micellar $\text{n}$-C₁₆H₃₃$\text{N}\text{+}$(CH₃)₂CH₂$\text{S}\text{+}$(CH₃)₂, 2CF₃SO₃^? rapidly methylates bound thiophenoxide ions.     

Action of tert-butyl azidoformate on the conjugate bases of 1,2,3,4-tetrahydro-9H-carbazole and other indole derivatives

tert-Butyl azidoformate ($\text{2}$) reacts with the conjugate bases of $\text{3a}$, $\text{7a}$, $\text{9}$ (R¹ = R² = CH₃), and $\text{9}$ (R¹ = CH₃, R² = H) to give products [$\text{4}$, $\text{8}$, $\text{12}$, and $\text{14}$, respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives.     

Haloacetylated enol ethers. 14 [6]. Reaction of β-alkoxyvinyl trifluoromethyl ketones with N-methylhydroxylamine

The reaction of a series of β-methoxyvinyl trifluoromethyl ketones [CF₃COC(R²)?C(OMe)R¹, where R¹ = Me, -(CH₂)₃-C3, -CH₂)₄-C3, Ph and R² = H, Me, -(CH₂)₃-C4, -(CH₂)₄-C4] with N-methylhydroxylamine is reported. The regiochemistry of the reaction are explained by MO calculation data.     

The reaction of 2-trifluoromethyl-3,3-difluorooxaziridine with nucleophiles.

The facile reactions of CF₃$\text{NCF}{}_2\text{O}$ with a variety of non-fluorinated nucleophiles are discussed. CF₃$\text{NCF}{}_2\text{O}$ + Nu^- → CF₃N(Nu)C(O)F + F^- Reactions with alcohols, carboxylic acids, mercaptans, amines, KSCN, KCN, NaN₃ and NaOCN were carried out. All except NaN₃ and NaOCN were reactive and the expected compounds were isolated in most cases. Subsequent reaction of CF₃N(Nu)C(O)F with additional nucleophile was observed in many cases forming CF₃N(Nu)C(O)Nu. With CH₃CO₂H, the latter reaction forms CH₃C(O)F and the novel amine CF₃N(H)OC(O)CH⁶₃. Ten new compounds are reported with characterization by IR, NMR and physical properties.     

Some diels—alder reactions of η1-bonded cyclopentadienylmetal compounds

Bis(cyclopentadienyl)mercury readily undergoes Diels—Alder reactions with RCCR (R = CO₂Me or CF₃), CF₃CFCFCF₃, CF₃CFCF₂, (CF₃)₂CC(CN)₂, C₂(CN)₄ and Ph$\text{NCONNC}$O to give stable adducts characterised by¹H, ¹⁹F and ¹³C NMR, spectroscopy. Similar reactions of CF₃CCCF₃ and CF₃CFCFCF₃ with the cyclopentadiene derivatives Me₃MC₅H₅ and (Me₃M)₂C₅H₄ (M = Si, Sn) are also described.     

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.     

sp C-H bond functionalization of methyl n-alkyl ketones [MeCOCnH2n+1 (n = 6-8)] as a novel method for the one-pot regioselective synthesis of ‘bifunctional alkanes’ with remote functional groups

Selective one-pot functionalization of methyl n-alkyl ketones, C_nH_2n+1COMe (n = 6-8) involving C-sp³-H bond cleavage with CO and various nucleophilic substrates [ⁱPrOH, BuCH(Et)CH₂OH, CF₃CH₂OH, (CF₃)(Me)CHOH, H(CF₂)₂CH₂OH, HCCCH₂OH, furan, thiophene, and anisole] in the presence of the superelectrophilic system CBr₄·2AlBr₃ has been performed for the first time.     

Synthesis of α-chloropolyfluoroalkyl ethers and acetals based on them

α-Chloropolyfluoroalkyl ethers were synthesized by the reaction of polyfluorinated alcohols H(CF₂CF₂) _n CH₂OH (n=1?3) with aliphatic aldehydes (ethanal, propanal, butanal) and hydrogen chloride. Yield of α-chloroethers decreases from 71 to 61% as the number of carbon atoms in the starting reactants increases. α-Chloropolyfluoroalkyl ethers react with polyfluorinated alcohols (n = 1?3) to form acetals in yield of up to 40–61%, and with methanol and ethanol, up to 98%.