Ethyl hexafluorophosphate

The N-coordinated compound [AuCljL] (L= l-ethyl-2-phenylimidazole) with silver tetrafluoroborate gives the cycloaurated species 102, which on further reaction with triphenylphosphine and sodium tetrafluoroborate or ammonium hexafluorophosphate forms the cationic complexes 103 (X = BF., PF,) (00JCS(D)271). 

This area of research has only recently attracted the attention of synthetic organic chemists, but there has been a flurry of impressive activity in the area. Simple (i. e., unstabilized) carbenes suffer from many of the problems of nitrenes (vide infra) and most reported synthetically useful procedures use carbenoids the majority of recent reports have focussed upon reactions between a-diazoesters and imines in the presence of a range of catalysts. In one of the earliest reports of enantioselective carbene-imine reactions, for instance, Jacobsen and Finney reported that ethyl diazoacetate reacts with N-arylaldimines in the presence of cop-per(i) hexafluorophosphate with mediocre stereoselectivity to give N-arylaziridine carboxylates. Though the diastereoselectivities of the reaction were often acceptable (usually >10 1, in favor of the cis isomers) the observed enantioselectivity was low (no more than 44% ee Scheme 4.27) [33],... 

In most cases diazonium salts are not isolated, but are converted into products by reactions that can be carried out in situ. Moreover, it is actually recommended not to isolate these salts, not even for purification purposes, as many of them have a tendency to explode. In addition, the high solubility of most diazonium salts in water makes precipitation from this medium difficult. Therefore, to obtain solid diazonium salts the recommended method for many decades was to carry out diazotizations in ethanol followed by precipitation with ether. As inorganic salts of nitrous acid are scarely soluble in ethanol, Knoevenagel recommended alkyl nitrites (ethyl or isopentyl nitrite) as diazotization reagents as long ago as 1890. Various other solvents have subsequently been used for diazotizations with alkyl nitrites (see Saunders and Allen, 1985, p. 23 ff.), but as a method for obtaining solid diazonium salts this has been superseded by the isolation of diazonium tetrafluoroborates and, to a lesser degree, of hexafluorophosphates. 

Relative rates of alkylation of toluene and benzene using a mixture of nitro-sonium hexafluorophosphate, nitromethane (or acetonitrile) and aliphatic amine as the alkylations agent have been determined at 25 °C as follows360 1.5 (ethyl-amine), 2.5 (i-propylamine) and 3.5 (benzylamine) nothing more as yet is known about the kinetics of alkylation with these new alkylating reagents. 

Lipases from C. antarctica and P. cepacia showed higher enantioselectivity in the two ionic liquids l-ethyl-3-methylimidazolium tetrafluoroborate and l-butyl-3-methylimidazolium hexafluoroborate than in THE and toluene, in the kinetic resolution of several secondary alcohols [49]. Similarly, with lipases from Pseudomonas species and Alcaligenes species, increased enantioselectivity was observed in the resolution of 1 -phenylethanol in several ionic liquids as compared to methyl tert-butyl ether [50]. Another study has demonstrated that lipase from Candida rugosa is at least 100% more selective in l-butyl-3-methylimidazolium hexafluoroborate and l-octyl-3-nonylimidazolium hexafluorophosphate than in n-hexane, in the resolution of racemic 2-chloro-propanoic acid [51]. 

The microwave-assisted thionation of amides has been studied by Ley and coworkers using a polymer-supported thionating reagent [115]. This polymer-supported amino thiophosphate serves as a convenient substitute for its homogeneous analogue in the microwave-induced rapid conversion of amides to thioamides. Under microwave conditions, the reaction is complete within 15 min, as opposed to 30 h by conventional reflux in toluene (Scheme 7.95). The reaction has been studied for a range of secondary and tertiary amides and GC-MS monitoring showed that it proceeded almost quantitatively. More importantly, this work was the first incidence of the use of the ionic liquid l-ethyl-3-methylimidazolium hexafluorophosphate... 

These changes in anion and cation were not merely a case of methyl, ethyl, propyl, butyl, and then futile. The change of anion dramatically affects the chemical behavior and stability of the ionic liquid the change of cation has a profound effect on the physical properties, such as melting point, viscosity, and density readily can be seen by examining the phase diagrams for the hexafluorophosphate and tetrafluoroborate salts (see Figures 5.5 and 5.6, respectively). 

While nitramines are formed from the reaction of secondary amines with nitronium salts the success of the reaction depends on the basicity of the amine (Equation 5.11). Thus, amines of low to moderate basicity are A-nitrated in good yields. The nitration of more basic amines is slow and the nitrosamine is often observed as a significant by-product, a consequence of the partial reduction of the nitronium salt to the nitrosonium salt during the reaction. Increased reaction temperature is also found to increase the amount of nitrosamine formed. The amine substrate is usually used in excess to compensate for the release of the strong mineral acid formed during the reactions. Both nitronium tetrafluoroborate and the more soluble hexafluorophosphate are commonly used for A-nitrations. Solvents like acetonitrile, methylene chloride, nitromethane, dioxane, sulfolane, ethyl acetate and esters of phosphoric acid are commonly used. 

N-Ethyl-N -(dimethylaminopropyl)carbodiimide-HCl Pentafluorophenyldiphenylphosphinate 0-(7-Azabenzotriazolyl)-N,N,N, N -tetramethyluronium hexafluorophosphate... 

The Heck reaction is a C-C coupling reaction where an unsaturated hydrocarbon or arene halide/triflate/sulfonate reacts with an alkene in presence of a base and Pd(0) catalyst so as to form a substituted alkene. Kaufmann et al. showed that the Heck reaction carried out in presence of ILs such as tetra-alkyl ammonium and phosphonium salts without the phosphine ligands, resulted in high yields of product. They attributed the activity to the stabilizing effect of ammonium and phosphonium salts on Pd(0) species. Carmichael et al. used ionic liquids containing either A,A -dialkylimidazolium and A-alkylpyridinium cations with anions such as halide, hexafluorophosphate or tetrafiuoroborate to carry out reactions of aryl halide and benzoic anhydride with ethyl and butyl acrylates in presence of Pd catalyst. An example of iodobenzene reacting with ethyl acrylate to give trans-et vy cinnamate is shown in Scheme 14. 

Shariati, A. and Peters, C. J., High-pressure phase behavior of systems with ionic liquids Measurements and modeling of the binary system fluoroform + l-ethyl-3-methylimidazolium hexafluorophosphate, /. Supercrit. Fluids, 25, 109, 2003. 

Fuller, J., Carlin, R. T., DeLong, H. C., and Haworth, D., Structure of 1-ethyl-3-methylimidazolium hexafluorophosphate Model for room temperature molten salts, Chem. Commun., 299-300, 1994. 

Bisglycidylacrylate, ethoxylated bisphenol A dimethacrylate, diurethane dimethacrylate, triethyleneglycol dimethacrylate, tricycle[5.2.1.02,6]decanedimethanol diacrylate, camphorquinone, ethyl 4-(/V,/V-dimcthylamino)benzoate, diphenyl iodonium hexafluorophosphate, 2,6-di-t-butyl-4-methylphenol, benzotriazole... 

ALCOHOLS Allyltrimethylsilane. (1,5-Cyclooctadiene)bis(methyldiphenylphos-phine)iridium hexafluorophosphate. Guaiacylmcthyl chloride. Lcvulinic acid. (3-( Primethylsilyljethoxymethyl chloride. 2-(Trimethylsilyl)ethyl chloroformate. Trimelhyllrityloxysilane. 

Addition of concentrated hexafluorophosphoric acid to a mixture of iosobutyric anhydride and 3-ethyl-3-pentanol leads to 4-ethyl-2,6-diisopropyl-3,5-dimethylpyrylium hexafluorophosphate, a reaction that proceeds via a rapid exothermal diacylation (Equation 466) <2004JOC536>. 

The organolithium compound (214) is obtained by treatment of the tetrathiafulvalene (5) with lithium diisopropylamide (LDA). This lithium compound (214) can further react with carbon dioxide, ethyl chloroformate, acetyl chloride, formaldehyde, dimethyl sulfate, and triethyloxonium hexafluorophosphate to produce the correspondingly substituted tetrathiafulvalenes (215) (79JOC1476). 

Analogous to epoxides, aziridines can be prepared by the methylenation of imines. In this case, ethyl diazoacetate is the most common source of carbenes. For example, the imine derived from p-chlorobenzaldehyde 148 is converted to the c/j-aziridinyl ester 149 upon treatment with ethyl diazoacetate in the presence of lithium perchlorate <03TL5275>. These conditions have also been applied to a reaction medium of the ionic liquid l-n-butyl-3-methylimidazolium hexafluorophosphate (bmimPFe) with excellent results <03TL2409>. An interesting enantioselective twist to this protocol has been reported, in which a diazoacetate derived from (TJ)-pantolactone 150 is used. This system was applied to the aziridination of trifluoromethyl-substituted aldimines, which were prepared in situ from the corresponding aminals under the catalysis of boron trifluoride etherate <03TL4011>. 

Ethyl 7-(4-Acetylpiperazin-1 -yl)- l-ethyl-6-fluoro-4-oxo-I,4-dihydro-1,8-naphthyridine-3-carboxylate (26) Typical Procedure for Diazotization/Thermal Fluorodediazoniation via Arenediazonium Hexafluorophosphates 81... 

Thiazol-2-yl allyl sulfides react with organomagnesium compounds in the presence of CuBr to afford optically active alkenes in good yields and selectivities <1996T10799>. Thiazole and benzothiazole allyl sulfides have been shown to react with excess ethyl diazoacetate in the presence of a copper(i) hexafluorophosphate acetonitrile complex to give, via formation of the resultant homoallylic sulfide intermediates, conjugated dienoic esters in good yields <1997TL3289>. /3-Ketosulfides of benzothiazole 143 are very prone to deprotonation by weak bases. Treatment... 

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