Thermal decomposition of some perfluoroalkyl grignard reagents. Synthesis of trans-1-halo and trans-1-alkylperfluorovinyl compounds

The thermal decomposition of perfluoroalkyl Grignard reagents (R_fMgX), formed from halogen-metal exchange with alkyl Grignard reagents, provides a good synthetic route to trans-1-haloperfluorovinyl compounds.

The decomposition of R_fMgX (where X = Cl, Br, I) in the presence of RMgX generally leads to a mixture of trans-1-alkylperfluorovinyl and trans-1-haloperfluorovinyl compounds. However, the choice of RMgX with respect to both the alkyl group and halogen is critical as regards the formation of the trans-1-alkylperfluorovinyl compounds.Several possible mechanisms are suggested to account for the experimental observations.     

Fluoro-ketones IV. Synthesis of phenylperfluoroalkyl ketones - mechanism of reaction between phenyllithium and fluoroesters

Although fluorine containing ketones (R_fC(O)R_f and R_fC(O)R, R_f = perfluoroalkyl) have been prepared from the reaction between organolithium reagents and perfluoroalkyl esters, the reaction has not found general applicability. Variable yields of ketones and co-production of secondary and tertiary alcohol by-products have in most instances been experienced. We have examined in more detail the factors e.g., temperature, mode of addition and perfluoroalkyl ester structure which influence ketone product and by-products formation. By controlling experimental conditions excellent yields of C₆H₅C(O)R_f compounds can be attained. A lithium salt of a hemiketal (II) has been isolated and shown to be the active intermediate in the production of the ketone. The stability of the salt and its potential reaction with the solvent dictates the type of reaction products. Low temperature favors stability of the lithium salt of the hemiketal whereby high yields of ketones are produced on hydrolysis.     

A new method for the preparation of α-(perfluoroalkyl) carbonyl and γ-(perfluoroalkyl)-α,β-unsaturated carbonyl compounds

R_fI(Ph)OSO₂CF₃ or R_fI(Ph)OSO₃H smoothly reacted with various trimethylsilyl enol ethers under mild conditions to give α-(perfluoroalkyl) carbonyl and γ=(perfluoroalkyl)-α,β-unsaturated carbonyl compounds in high yields.     

Study on the reactions of fluoroalkanesulfonyl azides with N-alkylindoles

The reactions of fluoroalkanesulfonyl azides R_fSO₂N₃1 with N-alkylindoles 2 have been studied in detail. It was found that both solvent and the amount of the azides seriously affected the product distribution. 1 reacted with an equimolar amount of 2 in ether or 1,4-dioxane affording 2-(N-substituted-indolinylidene)fluoroalkane sulfonylimines 3 as major product; While, the treatment of 2 with two equivalent of 1 in ethanol afforded N-substituted-2-fluoroalkanesulfonimino-3-diazo-indolines 4 as an unexpected product in good yields. The reaction mechanism was discussed.     

Reactions of quadricyclane with fluorinated nitrogen-containing compounds. Synthesis of 3-aza-4-perfluoroalkyl-tricyclo[4.2.1.0]non-3,7-dienes

The cycloaddition reactions of quadricyclane (1) and polyfluorinated imines and nitriles were studied. Both (CF₃)₂CNH and (CF₃)₂CN(2-FC₆H₄) were found to have low reactivity towards 1, giving the corresponding [2 + 2 + 2] cycloadducts in a low yield. C₂F₅NCFCF₃ however, reacts with 1 rapidly, giving a mixture of two isomeric cycloadducts in a high yield. Perfluoroalkyl nitriles R_fCN (R_f = CF₃, C₂F₅, n-C₃F₇) were found to have surprisingly high reactivity to 1 producing exo-3-aza-4-(fluoroalkyl)-tricyclo[4.2.1.0^2,5]non-3,7-dienes in 56-81% yields at elevated temperature. Exo-3-aza-4-(perfluoroalkyl)-tricyclo[4.2.1.0^2,5]non-3,7-dienes rapidly react with CF₃Si(CH₃)₃ in the presence of CsF catalyst. The reaction results in addition of CF₃Si(CH₃)₃ across the CN bond of the azadienes with selective formation of only one stereoisomer of exo-3-aza-3-(trimethylsilyl)-4,4-bis(perfluoroalkyl)-tricyclo[4.2.1.0^2,5]non-7-enes. Silyl group in this compounds can be removed either by the action of tetrabutylammonium fluoride hydrate, leading to the formation of the corresponding amine after hydrolysis, or by reaction with HCl resulting in the formation of the corresponding amine hydrochloride.     

Synthesis and repellent properties of vinylidene fluoride-containing polyacrylates

Fluorinated polyacrylats with side group containing vinylidene fluoride (VDF) units (CF₃(CF₂)_n (CH₂CF₂)_m, n = 3, 5; m = 1, 2) were successfully synthesized. The water and oil repellency properties of these polymers are similar to those of fluorinated polyacrylate with side group containing long perfluorooctyl group (CF₃(CF₂)₇). The thermal telomerization of CF₃(CF₂)₅I and CF₃(CF₂)₃I with vinylidene fluoride (VDF) provided CF₃(CF₂)₅CH₂CF₂I (1b) and CF₃(CF₂)₃CH₂CF₂CH₂CF₂I (1c), respectively. The addition of 1b with ethylene followed by hydrolysis gave CF₃(CF₂)₅CH₂CF₂CH₂CH₂OH (2b). Treatment of 1c with ethyl vinyl ether in the presence of Na₂S₂O₄ followed by reduction produced CF₃(CF₂)₃CH₂CF₂CH₂CF₂CH₂CH₂OH (2c). Fluoroacrylates 3b-d were prepared by acrylation of the corresponding fluoroalcohols 2b-d. The semi-continuous process emulsion co-polymerization of 3a-d with octadecyl acrylate and 2-hydroxylethyl acrylate initiated by (NH₄)₂S₂O₈ in the presence of a mixture emulsifiers of polyoxyethylene(10)nonyl phenyl ether (TX-10) and sodium lauryl sulfate provided stable latexes 4a-d, respectively. The water and oil repellency properties of 4b (R_f: CF₃(CF₂)₅CH₂CF₂) and 4c (R_f: CF₃(CF₂)₃CH₂CF₂CH₂CF₂) containing vinylidene fluoride (VDF) units were similar to those of 4a (R_f: CF₃(CF₂)₇) containing long perfluoroalkyl group and much better than those of polymer 4d (R_f: CF₃(CF₂)₃) with short perfluoroalkyl chain. Thus, polyacrylates containing vinylidene fluoride units showed promising aspects as the alternatives to the currently used water and oil repellent agents with long perfluoroalkyl chains.     

New axially dissymmetric ligand recoverable with fluorous solvent

Axially dissymmetric ligands with perfluoroalkyl groups, (Ra)-2,2′-bis[(R)-1-hydroxy-1H-perfluorooctyl]biphenyl [(Ra)-(R)₂-1c] and its enantiomer, have been synthesized successfully by the coupling reaction of the corresponding aryl bromide using Ni(COD)₂. These ligands showed much higher asymmetric induction in the reaction of various aldehydes with diethylzinc than the trifluoromethyl (1a) or pentafluoroethyl (1b) analogues. Furthermore, 1c was recovered quantitatively by extraction with a fluorous solvent from the reaction mixture due to its high fluorine content. The recovered ligand 1c was pure enough to be reused without purification. The efficiency of 1c as the chiral ligand was not decreased at all even after seven times recycling.     

Novel electrolyte salts based on perfluoroalkyltrifluoroborate anions: 1. Synthesis and characterization

Lithium and tetraethylammonium perfluoroalkyltrifluoroborate salts, Li[R_fBF₃]·H₂O and Et₄N[R_fBF₃] (R_f=C₂F₅, n-C₃F₇ and n-C₄F₉), were prepared from the reactions of perfluoroalkylmagnesium reagents (R_fMgBr) and B(OCH₃)₃, followed by fluorination by aq.KHF₂ and aq.HF solutions and the cation exchange reaction of the resultant K[R_fBF₃]. All the salts prepared were characterized by NMR, NMR, NMR, NMR, IR, MS and elemental analysis.     

The asymmetric addition of malononitrile to α,β-unsaturated ketones catalyzed by RuCl2[(R,R)-DPEN](PPh3)2 as the precatalyst

Non-borohydride ruthenium complex, RuCl₂[(R,R)-DPEN](PPh₃)₂ (1f), was demonstrated to catalyze asymmetric Michael addition of malononitrile to acyclic enones with weak bases. Michael addition of malononitrile to chalcone and analogues was promoted by combining CsOAc with CsOH in the presence of 1f and gave good yields and up to 82% ee.     

Stereospecific synthesis of chiral tertiary alkyl-aryl ethers via Mitsunobu reaction with complete inversion of configuration

Mitsunobu reaction of chiral tertiary alcohol (S)-2 with phenol 3 provides the desired ether (R)-1 in moderate yields at elevated temperatures (80-100°C). The S_N2 displacement pathway is evident by complete inversion of the (S)-alcohol to (R)-ether.     

Perfluoroalkylphosphines and arsines obtained by Pd-catalyzed cross-coupling reaction with organoheteroatom stannanes

Pd-catalyzed cross-coupling reaction of organoheteroatom stannanes containing elements of the groups 15 (P, As) and 16 (Se) with perfluoroalkyl iodides (R_fI) was studied. Herein, a one-pot two-step reaction to form P–R_f, As–R_f and Se–R_f bonds is reported. The stannanes n-Bu₃SnZPh_n (Z = P, As, Se; n = 1–2) were generated in situ by the reaction of the Ph_nZ⁻ anion with n-Bu₃SnCl. The cross-coupling reactions of these stannanes with R_fI afforded C-heteroatom products, new perfluoroalkylarsines and perfluoroalkylselenides in good yields (47–90%) and perfluoroalkylphosphines in moderate yields (15–48%).     

Reactions of perfluoroalkyl iodides with CC-multiple bonds induced by transition metal centers

Additions of perfluoroalkyl iodides R_FI to 1-alkenes can be catalyzed by transition metals, especially by noble metals such as ruthenium or platinum. Complexes of group VI–VIII metals in low oxidation states are even more effective and may also be employed for the addition of R_FI to alkynes. Heterogeneous metal catalysts facilitate the transfer of the perfluoroalkyl group from R_FI to aromatic ring systems.Iodo-perfluoroalkanes 1 belong to the most important intermediates in organofluorine chemistry [1]. The addition of 1 to alkenes according to

is known to be a radical process which can be initiated by means of heat, UV- or ?-radiation, electrocatalysis or by organic azo or peroxo compounds.     

Study the reactions of fluoroalkanesulfonyl azides with N-alkylindoles

The reactions of fluoroalkanesulfonyl azides R_fSO₂N₃1 with N-alkylindoles 2 have been studied in detail. It was found that both solvent and the amount of the azides seriously affected the product distribution. 1 reacted with equimolar of 2 in ether or 1,4-dioxane affording 2-(N-substituted-indolinylidene)fluoroalkane sulfonylimines 3 as major product; While, treatment of 2 with 2 equiv. of 1 in ethanol, an unexpected product N-substituted-2-fluoroalkanesulfonimino-3-diazo-indolines 4 were obtained in good yield. The reaction mechanism was discussed.     

Samarium diiodide-mediated reductive couplings of chiral nitrones with aldehydes/ketones and acyl chlorides

The SmI₂-mediated and H₂O-promoted reductive cross-coupling reactions of the l-tartaric acid derived nitrone (3S,4S)-8 with aldehydes/ketones, and the l-malic acid derived nitrone (S)-6 with aliphatic acyl chlorides have been investigated, respectively. (2R,3S,4S)-1,3,4-Trihydroxyprolinol derivatives 9a-f were obtained with high C-2/C-3 trans-selectivities, and 72:28-85:15 diastereoselectivities at the carbinol center from aromatic ketones/aldehydes, while low diastereoselectivities for aliphatic aldehydes. Conditions have been established for the syntheses of (2R,3S,4S)-3,4-dihydroxyprolinol derivatives such as 18, by N-O bond cleavage of the corresponding N-hydroxyprolinol derivatives 9b-f, or more conveniently by a one-pot reductive coupling of nitrone 8 and in situ N-O bond cleavage of the resultant coupling product. The 2-acyl-3-benzyloxy-1-hydroxypyrrolidines 10a-f were formed in 48-82% yields, and in 74:26-78:22 diastereoselectivities. It was revealed that the amount of water required for the reaction is substrate-depending.     

Unsymmetrically substituted triazacyclohexanes and their chromium complexes

The unsymmetrically N-substituted N,N′-Ar₂-N″-R-1,3,5-triazacyclohexanes 1–4 (Ar = ortho- or para-fluorophenyl, R = n- or iso-propyl) can be obtained in good yields from a one-step condensation reaction with excess amine. Solid state structures of 1–4 resemble closely those of their triaryl-substituted analogues. The condensation reaction to 4 was looked at by detailed NMR investigations and revealed that amine/aniline exchange is occurring in solutions containing free aniline even at ambient conditions setting up an equilibrium between all possible symmetrical and unsymmetrical triazacylcohexanes. Selective crystallisation of 4 from the solution drives the reaction to high yields of 4. Complexes 1–4 react readily with CrCl₃ or CrCl₃(THF)₃ to form the corresponding CrCl₃ complexes. The complexes are insoluble in non-polar solvents and decompose under decomplexation in coordinating solvents.     

Asymmetric reduction of perfluoroalkyl ketones with chiral lithium alkoxides

Reduction of perfluoroalkyl ketones with chiral lithium alkoxides gave chiral α-perfluoroalkyl alcohols in high enantiomeric excesses. Interestingly, reaction of 2,2,2-trifluoroacetophenone (1) with lithium (S)-1-phenylethoxide (2) gave (S)-2,2,2-trifluoro-1-phenylethanol (3), while the same reaction of perfluorooctan-1-one (7) with 2 gave (R)-1H-1-phenylperfluorooctanol (8). Based on the speculation of mechanism, the order of steric effects on this reaction is estimated as C₇F₁₅ > substituted phenyl > CF₃.     

Fluorination of perfluoroalkylsulfenyl chlorides,perfluorodialkyl disulfides and perfluorodialkyl sulfides with chlorine monofluoride

In reactions with perfluoroalkylsulfenyl chlorides (R_fSCl; R_f = F₃, C₂F₅, n-C₃F₇, n-C₄F₉) and perfluoroalkyl disulfides (R_fSSR_f′; R_f = R_f′ = CF₃, R_f = CF₃, R_f′ = C₂F₅) at 25°, chlorine monofluoride acts primarily as a chlorinating and fluorinating reagent to give the corresponding perfluoroalkylsulfur chloride tetrafluorides, R_fSF₄Cl, in good yields. However, small amounts of perfluoroalkylsulfur pentafluorides, R_fSF₅, are also obtained. A mixture of the cis and trans isomers of bis(trifluoromethyl)sulfur tetrafluoride and of trifluoromethyl pentafluoroethylsulfur tetrafluoride has been formed by the reaction of the corresponding bis(perfluoroalkyl) sulfides and chlorine monofluoride. The new perfluoroalkylsulfur chloride tetrafluorides are colorless, unpleasant smelling liquids. The infrared, mass and ¹⁹F NMR spectral data, as well as thermodynamic and elementary analysis data, are given for the new compounds.     

Intramolecular cyclization of lithium 4,4-dimethoxy-1-(perfluoroalkyl)pentane-1,3-dionates on treatment with boron trifluoride diethyl etherate

Lithium 4,4-dimethoxy-1-(perfluoroalkyl)pentane-1,3-dionates react with BF₃?Et₂O to give 2-methoxy-2-methyl-5-(perfluoroalkyl)furan-3(2H)-ones in high yields.     

Synthesis of new 1-substituted 4-perfluoroalkyl tetrazol-5-ones

1,3-Dipolar cycloaddition of perfluoroalkyl ethyle azides 1 with isocyanates 2 afforded 1-perfluoroalkyl-4-(n-Bu, phenyl or mesitylsulfonyl) tetrazol-5-ones 3 in good yields. The use of perfluoroalkyl ethyl azides extends the reaction to the less reactive n-butyl isocyanate.