Acids Hydrofluoric acid-Acetonitrile

Benzeneselenenyl halides, 26 Camphor- 10-sulfonic acid, 62 Dicyclohexylcarbodiimide-4-Dimethyl-aminopyridine, 107 Hydrofluoric acid-Acetonitrile, 188 Thiophenol, 297 Lithiation (see Metallation)... 

Aqueous hydrofluoric acid dissolved in acetonitrile is a good catalyst for intramolecular Diels-Alder reactions [9] This reagent promotes highly stereoselective cyclizations of different triene esters (equation 8) The use of other acids, such as hydrochloric, acetic, and trifluoroacetic acid, results in complete polymerization of the starting trienes [9] (equation 8)... 

The completion of the synthesis of 1 only requires two deprotection steps. Hydrogenolysis of the four benzyl ethers, followed by cleavage of the triisopropylsilyl ether with hydrofluoric acid in acetonitrile, provides paeoniflorin (1) in an overall yield of 92 %. 

Bromine trifluoride is also used to convert the cyano group in acetonitrile, chloroacetonitrile, and propionitrile into the trifluoromethyl substituent. The reaction is carried out using hydrofluoric acid as a solvent.126... 

Upon completion of the synthesis, the peptide was cleaved from the resin by treatment with liquid hydrofluoric acid (HF) for 45 minutes at 0°C. The HF was evaporated and the peptide treated with aqueous acetic acid and lyophilized. The crude peptide was then purified by high performance liquid chromatography (HPLC) on a C18 column, eluting with a mixture of acetonitrile and 0.1% TFA in water. Purified fractions (homogeneous by UV and TLC analysis) were combined and lyophilized. Analytical HPLC was used to determine the purity of the final product peptides synthesized was at least 98% pure. 

Moreover, the electrochemical fluoroacetamidation of cycloalkenes was carried out in acetonitrile with tetraethylammonium fluoride/hydrofluoric acid, in order to obtain fluoroac-etamides 16 and 17, although in low yield. cw-Compounds are the major components of the reaction mixture, as determined by H NMR. This result was ascribed to the acetonitrile addition to the /1-fluorocarbocation absorbed on the electrode surface185-186. 

Preparation The reagent can be prepared by neutralization of a 10% aqueous solution of teira-n-hutylammonium hydroxide with 48% hydrofluoric acid, concentration under reduced pressure, drying by azeotropic distillation under reduced pressure using 1 1 benzene-acetonitrile, and final drying at 30° and 0,5 mm. for 20 hr. For another preparation see Fowler et al. ... 

Thus treating a pyridine/acetonitrile solution of (19) with hydrofluorous acid will lead to (20) in excellent yield. Subsequent cyclization to (21a, 21b) by treating (20) first with an ethanolic solution of sodium borohydride and cerium (III) heptahydrate, and second a two normal solution of hydrochloric acid. 

Commercially available silica particles (Kromasil, 13 pm mean diameter, C4-phase, 0.7 ml/g pore volume, 195 A pore size) are from Eka Chemicals AB (Bohus, Sweden). ( )-Isoproterenol HCl and (—)-isoproterenol HCl are purchased from Sigma (St. Louis, USA). (—)-Isoproterenol, trifluoromethacrylic acid (TFMAA), metha-crylic acid (MA A) and divinylbenzene (DVB) are obtained from Aldrich (Steinheim, Germany). DVB is of technical grade (80%) and the inhibitor is removed using basic alumina (Merck, Darmstadt, Germany) prior to use. Solvents for polymer preparation are of anhydrous quality and are from Labscan (Dublin, Ireland). Hydrofluoric acid (HF), acetone (p.a.) and acetonitrile (MeCN)(HPLC quality) are obtained from Merck. 

Protection of Alcohols. Di-r-butylsilyl bis(trifluoromethane-sulfonate) is a reagent for the selective protection of polyhydroxy compounds. This reagent reacts with 1,2-, 1,3-, and 1,4-diols under mild conditions to give the corresponding dialkylsilylene derivatives in high yield (0-50 °C, 79-96%). Deprotection is conveniently achieved by using aqueous hydrofluoric acid in acetonitrile (eq 1). 

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