Acidity in acetonitrile

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 %. 

H- and 3//-Azepines are generally unstable in aqueous acid solution and the few examples of simple azepinium salts, namely perchlorates,77 bromides,105 picrates35201 and a solitary iodide,105 have been prepared under nonaqueous conditions. The fractional crystallization of oxalate salts has been used for the separation of mixtures of 4- and 6-substituted 3f/-azepines,66 and 3,6-di-tm-butyl- and 2,5-di-tert-butyl-3//-azepine, on treatment with tetrafluoroboric acid in acetonitrile, are converted quantitatively into their crystalline tetrafluoroboratc salts.70... 

Figure 3. Cyclic voltammograms of 3-methylpyrrole-4-carboxylic acid in acetonitrile + 0.1 MEt4NC104.58 (Reprinted from P. G. Pickup, Poly-(3-methylpyrrole-4-carbox-ylic acid) An electronically conducting ion-exchange polymer, J. Electroanal. Chem. 225, 273-280, 1987, with kind permission from Elsevier Sciences S.A.)...

Non-Kolbe electrolysis of carboxylic acids in acetonitrile/water leads to acetamides as main products [294] (Table 10). The mechanism has been investigated by using " C-labeled carboxylic acids. The results are rationalized by assuming a reaction layer rich of carboxylate resulting in the formation of a diacylamide that is hydrolyzed... 

Eq. 25) [295]. A similar mechanism has also been proposed for the electrolysis of isobutyric and pivalib acid in acetonitrile [296]. As the intermediate alkyl cation can rearrange and the intermediate iminium cation can furthermore react with the starting carboxylic acid three different amides can be isolated (Eq. 26) [295 a]. The portion of the diacylamide can be considerably increased if the electrolyte consists of acetonitrile/ acetic acid [295 b]. 

Treatment of ninhydrin 431 with excess allyltrimethylsilane 82 and triflic acid in acetonitrile affords dehydrated ninhydrin 660 in 55% yield and the O-silylated product 661 in 18% yield [43] (Scheme 5.59). 

To test this hypothesis, the picolinamide 22 was prepared using in situ activated picolinic acid (Scheme 8.12). The in situ activation of picohnic acid was used because picolinyl chloride (available commercially as the HC1 salt) is relatively expensive. The coupling reaction was not straightforward, and the best results were obtained by adding 1.4equiv of thionyl chloride to a solution of 1.4equiv of picolinic acid in acetonitrile, followed by addition of triethylamine. As soon as the addition of triethylamine was complete, aniline 5 was introduced immediately because the activated picolinic acid was unstable in the presence of triethylamine. 

A thio-Claisen rearrangement174 was used for the regioselective synthesis of thiopyrano[2,3-b]pyran-2-ones and thieno[2,3-b]pyran-2-ones (Eq. 12.76). A convenient method for the aromatic amino-Claisen rearrangement of N-(l,l-disubstituted-allyl)anilines led to the 2-allylanilines being produced cleanly and in high yield by using a catalytic amount of p-toluenesulfonic acid in acetonitrile/water (Eq. 12.77).175... 

Another example of an intramolecular cyclization initiated by reactions of an acyliminium ion [32] with an unactivated alkene has been published by Veenstra and coworkers. In their total synthesis of CGP 49823 (1-116), a potent NK antagonist [33], these authors treated the N,O-acetal 1-112 with 2 equiv. of chlorosulfonic acid in acetonitrile to afford acyliminium ion 1-113 (Scheme 1.29) [34]. This is qualified for a cyclization, creating piperidine cation 1-114, which is then trapped by... 

Khashaba et al. [34] suggested the use of sample spectrophotometric and spectrofluorimetric methods for the determination of miconazole and other antifungal drugs in different pharmaceutical formulations. The spectrophotometric method depend on the interaction between imidazole antifungal drugs as -electron donor with the pi-acceptor 2,3-dichloro-5,6-dicyano-l,4-benzoquinone, in methanol or with p-chloranilic acid in acetonitrile. The produced chromogens obey Beer s law at Amax 460 and 520 nm in the concentration range 22.5-200 and 7.9-280 pg/mL for 2,3-dichloro-5,6-dicyano-l,4-benzoquinone and p-chloranilic acid, respectively. Spectrofluorimetric method is based on the measurement of the native fluorescence of ketoconazole at 375 nm with excitation at 288 nm and/or fluorescence intensity versus concentration is linear for ketoconazole at 49.7-800 ng/mL. The methods... 

Hufford et al. [13] determined the dissociation constants of primaquine by titration with 0.1 N hydrochloric acid in acetonitrile-water mixture and values were extrapolated to water by using linear regression analysis. 

Hufford et al [13] used a 13C NMR spectroscopic method for the assignments of dissociation constants of primaquine. The first and second dissociation constants of primaquine were determined by titration with 0.1 N hydrochloric acid in acetonitrile-water mixtures and values were extrapolated to water by using linear regression analysis. The assignments of the dissociation constants were unambiguously achieved by studying the 13C NMR spectral data obtained with monohydrochloride, dihydrochloride, and trihydrochloride salts. 

The triazinoisoquinoline 151 was prepared by cyclocondensation of the diaminoisoquinoline derivative 150 with biacetyl. Treatment of 151 with ethanesulfonic acid in acetonitrile gave the triazinoisoquinolinium salt 152, which is useful as a local anesthetic, antidepressant, tranquilizer, sedative, and muscle relaxant (89GEP3833615). 

Thymidine has been selectively sulfated at HO-5 by using chloro-sulfonic acid in acetonitrile in the presence of pyridine.207... 

The cartridge was preconditioned with 0.5 mL toluene and each of the above benzodiazepine solutions passed through it. Analytes retained on the MIP were eluted with 0.5 mL of 15% acetic acid in acetonitrile. Internal standard (corresponding deuterated benzodiazepine) was added and subjected to LC/MS/MS. The results obtained for recovery, limit of detection (LOD), and quantitation (LOQ) are shown in Table 1.22. The binding capacity of diazepam to the templated MIP was found to be 110 ng/mg polymer. The same results were obtained for postmortem hair samples. 

Copper-catalyzed monoaddition of hydrogen cyanide to conjugated alkenes proceeded very conveniently with 1,3-butadiene, but not with its methyl-substituted derivatives. The most efficient catalytic system consisted of cupric bromide associated to trichloroacetic acid, in acetonitrile at 79 °C. Under these conditions, 1,3-butadiene was converted mainly to (Z )-l-cyano-2-butene, in 68% yield. A few percents of (Z)-l-cyano-2-butene and 3-cyano-1-butene (3% and 4%, respectively) were also observed. Polymerization of the olefinic products was almost absent. The very high regioselectivity in favor of 1,4-addition of hydrogen cyanide contrasted markedly with the very low regioselectivity of acetic acid addition (vide supra). Methyl substituents on 1,3-butadiene decreased significantly the efficiency of the reaction. With isoprene and piperylene, the mononitrile yields were reduced... 

FIGURE 9 Moderately rapid gradient separation. Column XTerra MS C, IS, 4.6x 20mm 3.5p.m. Gradient 0 to 100% B over 4min,A 0.1% formic acid in water, B 0.1% formic acid in acetonitrile. Flow rate 3.0mL/min. Temperature 30°C. Detection UV at 254 nm. Instrument Alliance 2795 with 996 photodiode array detector. Compounds (I) acetanilide, (2) triamcinolone, (3) hydrocortisone, (4) 2-amino-7-chloro-5-oxo-5H-[l]benzopyrano[2,3-b]pyridine-3-carbonitrile, (5) 6a-methyl-17a-hydroxyprogesterone, (6) 3-aminofluoranthene, (7) 2-bromofluorene, (8) perylene, (9) naphtho(2,3-a)pyrene. 

An interesting alternative to the use of chromium(VI) oxidants for the conversion of 1 to 2 involves the use of a low-valent iron reagent prepared in situ by the action of hydrogen peroxide on an iron(II) complex of 1 (73). Vinblastine (as the free base) is treated with 2 equiv of perchloric acid in acetonitrile at -20°C. Ferrous perchlorate is then added, followed by the addition of excess 30% hydrogen peroxide. Work-up of the reaction mixture with a saturated solution of ammonium hydroxide gives 2 in yields of 35-50% after chromatography. 

Triketone (57), a key intermediate in the synthesis of 4,4,7,7,11,11-hexanitropentacyclo [6.3.0.0 .0 °.0 ]undecane (61) (Zlj-hexanitrotrishomocubane), has been synthesized independently by both Marchand and co-workers, and Fessner and Prinzach. Marchand and co-workers prepared the trioxime (58) from the corresponding triketone (57). Oxidation of (58) with peroxytrifluoroacetic acid in acetonitrile provides a direct route to the trinitro derivative (59) in 35 % yield, this yield reflecting an efficiency of 70 % for the oxidation of each oxime group. Subsequent oxidative nitration of (59) with sodium nitrite and potassium ferricyanide in aqueous sodium hydroxide yields the target T>3-hexanitrotrishomocubane (61). 

Numerous synthetic routes to the dinitramide anion have been reported. Cesium dinitramide (149) has been synthesized via the fluoride-catalyzed /1-elimination of 1-(V,A1-dinitramino)-2-trimethylsilylethane (148) with cesium fluoride the latter prepared by treating 2-(trimethylsilyl)ethyl isocyanate with a solution of nitronium tetrafluoroborate and pure nitric acid in acetonitrile. ... 

Alkyl lV,lV-dinitramines (154) have been prepared from the reaction of the tetraalkylam-monium salts (155) of primary nitramines with nitryl fluoride in acetonitrile at subambient temperature. The same reaction with the primary nitramine or its alkali metal salts yields the corresponding nitrate ester. Treatment of the ammonium, potassium, or lithium salts of primary nitramines (156) with a solution of nitronium tetrafluoroborate in acetonitrile at subambient temperature yield alkyl iV,iV-dinitramines. ° The same reactions in ether or ester solvents enables the free nitramine to be used. The nitrolysis of A-alkylnitramides (157) and N,N-diacylamines with nitronium tetrafluoroborate in acetonitrile, and the nitration of aliphatic isocyanates with nitronium tetrafluoroborate and nitric acid in acetonitrile, also yield alkyl A,A-dinitramines (154). 

Brezinski B, Grech E, Malarski Z, Sobczyk L (1991) Protonation of l,8-bis(dimethylamino) naphthalene by various acids in acetonitrile. J Chem Soc Perkin Trans II 857-859... 

R = PhCHj, R2 = R3 = H R = Me, R" = H, R = NHAc) lost the thiol and produced the corresponding 2-hydroxycarbazoles (230) on treatment with p-toluenesulfonic acid in acetonitrile." Similarly the thioacetal 231 lost 1-mol equivalent of thiol and one of water, giving carbazole 232 in acetic acid. Ketone 233 gave the lactone 234 on dehydration with p-toluenesul-... 

The reaction of fluorine with water, producing hypofluorous acid (HOF) and subsequently oxygen difluoride (OF2), has been the subject of intensive study over the last fifty years.1 Additionally, hypofluorous acid in acetonitrile has been characterized.5 The reagents are potentially explosive and present a toxicity hazard similar to fluorine therefore, work should be carried out in an efficient hood and proper safety equipment is required. It was established in the earliest investigations that the reaction of hypofluorous acid with alkenes in nonpolar solvents gives fluoro hydrins, e.g. 1, in high yield.6 However, it is now clear that epoxides are initially formed in acetonitrile7 and 1,2-epoxycyclohexane (2) is formed in reactions with cyclohexene in various solvents.5... 

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