Acidic media, azides

A colorimetric procedure is described for the determination of small amounts of Compound 118 (1,2,3,4,10,10-hexa-chloro - 1,4,4a,5,8,8a - hexahydro - 1,4,.5,8 - dimethano-naphthalene). Reaction with phenyl azide to form a di-hydrotriazole derivative and subsequent treatment with diazotized dinitroaniline in strongly acid medium produce an intense red color. Amounts of the insect toxicant of 10 to 40 micrograms in the final 10-ml. aliquot are readily determined with a spectrophotometer. Commonly used insect toxicants do not interfere. 

The seemingly complex imidazolone (78-3) is in fact obtained in a single step by reaction of the amino-ester (78-1) with the iminoether (78-2) derived from capro-nitrile. The relatively acidic proton on the heterocyclic ring is next removed by reaction with sodium hydride. This anion is then alkylated with the same biphenyl-methyl bromide (77-2) that was used to prepare losartan to afford (78-4). The nitrile group is in this case converted to the tetrazole by means of tributyltin azide, a reagent that involves milder conditions than the traditional acidic medium used to generate hydrazoic acid. Thus, treatment of (78-4) with the tin reagent affords irbesartan (75-5) [82]. 

Preparation of 5-aminotetrazole monohydrate (AT) by treating dicyandiamide with sodium azide in acidic medium at 65 °C. 

The acid hydrolysis of the 2-aryl-1,3,4-oxadiazoles can be used for their analytical determination. The method used is either to break down the compound by heating with hydrochloric acid under reflux to give the acid hydrazide and then to titrate the hydrazide with iodide in bicarbonate solution,68, 69 or to titrate potentiometrically directly with sodium nitrite in a hydrochloric acid medium.128 In this way the acid hydrazide is formed in the first reaction step and is then converted into the insoluble azide by the sodium nitrite. 

The chemistry of tetrazol derivatives was reviewed by Bensen (192). The simplest and most versatile derivative is 5-aminotetrazol (Vol. Ill, p- 210). It is usually obtained by the method of Stolle and Schick [151] from cyanoguani-dine and sodium azide in an acid medium ... 

The oxidation of Cr to Cr207 is critical for the determination of Cr by the diphenylcarbazone method. The oxidation is normally done in acid medium with KMn04 or with (NH4)2S20s in the presence of silver ions. The excess of Mn04 is either decomposed by azide or precipitated as Mn02 aq in the presence of Mn ions. The excess of persulphate is either decomposed by boiling the solution or reduced by azide. Fusing solid samples with sodium carbonate or sodium peroxide converts Cr(III) into Cr(VI). Since the absorbance of the solution varies with acidity, the pH should be kept constant at the optimum value of pH 1... 

Transfer of an azide group from an azidothiazolium salt followed by cyclization in an acid medium can be a useful method of building a triazole ring (p. 263) tosyl azide is possibly a more convenient source of azide, and cyclization at ambient temperature in a basic medium is complete in about IS min. 

The successful synthesis of these compounds showed the feasibility of using the carbodiimidazole coupling reaction in the formation of aryl-azido ATP analogs. For the general synthesis of the arylazidocarboxylic acids, 4-fluoro-3-nitroaniline is first diazotized in a concentrated hydrochloric acid medium in the presence of sodium nitrite [Eq. (2)]. The diazonium salt is subsequently treated with sodium azide, which results in the formation of a light-sensitive 4-fluoro-3-nitrophenyl azide (IV) [Eq. (3) ]. The structure of (IV) has been confirmed by its melting point of 52°-52.5° (recrystallized from petroleum ether) its NMR spectrum, 7.47 ppm (2 protons), 7.78 ppm (1 proton) and its mass spectrum, m/e 182. 

Fluoro-3-nitroaniline (4.38 g, 0.028 mole) dissolved in 30 ml of concentrated HCl and 5 ml of water at 45° is filtered and then chilled to —20° in a Dry Ice-acetone bath. Sodium nitrite (2.4 g, 0.034 mole) in 5 ml of water is added slowly to the well stirred acid medium while the flask temperature is kept at —15° to —20°. The reaction mixture after a 10-min stirring is filtered into a flask at —20°. To this filtrate, sodium azide (2.2 g, 0.032 mole) dissolved in 8 ml of water is added drop-wise while the reaction mixture is stirred and kept in the dark at —15°... 

If aryl azides are irradiated in acidic medium in the presence of arenes, derivatives of diphenylamine are formed." For the diphenylnitrenium ion, G-complexes with benzene have been detected by laser flash photolysis. In reactions with alkenes, nitrenium ions react more rapidly with electron-deficient olefins. Rate constants for the reaction of diphenylnitrenium with electron-rich olefins such as cyclohexanone trimethylsilyl enol ether are of the order of 1.9 x 10 M" s". In the reaction of 2-fluorenylni-trenium with 2 -deoxyguanosine, reaction at C8 of the guanine base takes place. ... 

The cleavage of epoxides by water is a classical reaction. Such epoxide cleavage can be catalyzed by both acids and bases in aqueous media. In the presence of other nucleophiles, the corresponding nucleophilic ringopening products are obtained with the nucleophiles being incorporated into the products.68 Examples include azides, iodides, and thiols in the presence or absence of metal salts in aqueous media. The pH of the reaction medium controls the reactivity and regioselectivity of the... 

Sato et al. carried out detailed studies on the possibilities of transformation of tetrazolo[l,5-tf]pyrazines 54 to 2-aminopyrazines 56 < 1994S931 >. These authors found that the generally used methods for this conversion fail because the starting compound exists in the stable bicyclic form 54, whereas partial formation of the azide valence bond isomer 55 would be necessary for the success of the transformation. Application of special reaction conditions succeeded, however hydrogenation over palladium catalyst in the presence of ammonium hydroxide or treatment with stannous chloride in a mixture of methanol and hydrochloric acid solved this problem. Thus, a great number of derivatives of 54 was reduced to the corresponding 2-aminopyrazine 56 in medium to high yields (45-100%). 

The acylation of formamidoxime should lead to oxadiazoles unsubstituted in the 3-position. While benzoylation with benzoyl chloride is reported to give dibenzhydroxamic acid 45), 0-acylated formamidoxime could be prepared in good yields with acetic anhydride, the mixed anhydride of acetic and ethyl carbonic acid, benzoic anhydride and benzoyl azide. The cyclization of these esters of formamidoxime into 5-substituted oxadiazoles has been accomplished by heating in an aqueous medium. 

Curtius and Rissom [41] prepared cupric azide by the action of an aqueous solution of sodium azide on an aqueous solution of cupric sulphate, obtaining the salt in a hydrated form. The anhydrous salt was prepared by Straumanis and Ciru-lis [125] in the form of dark brown, reddish sediment by reaction of lithium azide on cupric nitrate in an alcohol solution. Another method described by Curtius consists of reacting hydrazoic acid with metallic copper in an aqueous medium. 

Benzylidene thio cqrbazoyl Azide Benzalthio carbazinic Acid Azide or (N-Benzylidene-N -azidomercapto)-hydrazine (called Benzalthio-carbazinsaureazid by Stolle), CgHg.CH N.NH.C-( S).N3 mw 205.30, N 34.12% pale yel flakes, mp 173°, followed by an expl sol in hot ale or hot AcOH insol in w was prepd by shaking for 8 hrs a mixt of dithiocarbazinic acid hydrazide, Na azide Pb oxide in ale medium... 

The yield from this reaction is greatest if the medium is alkaline, for nitrous acid attacks hydrazoic acid oxidizing it with the liberation of nitrogen. If hydrazine sulfate37 is used in the mixture, the resulting hydrazoic acid is not available for the preparation of lead azide until it has been distilled out of the solution. (Lead ions added to the solution would cause the precipitation of lead sulfate.) The reaction mixture may be acidified with sulfuric acid, a little ammonium sulfate may be added in order that the... 

Aryl azides (such as 13) can be easily prepared from their corresponding amines (12) in one or two steps. Three examples are given in Scheme 2a. The most common method is the diazotization of the amine with sodium nitrite under acidic conditions (giving diazonium species 14), followed by addition of sodium azide in an aqueous medium (route i in Scheme 2a) [44], In 2003, the synthetic method was improved by application of triflyl azide (TfN3), which allowed a one-step conversion and gave improved yields (route ii in Scheme 2a) [45]. Recently, the development of sulfonyl azides 15 (with R = imidazole [46] or R = benzotriazole [47]) was reported these proved to be more stable reagents and allowed a conversion under mild conditions (route iii in Scheme 2a). 

Examples of very highly sensitive substances are mixture of chlorates-red phosphorus, paper cracker, lead azide, and DDNP. High sensitivity substances are dynamite(powder), PETN(powder), HMX(powder), RDX(powder), tetryKpowder), picric acid(powder), TNT(powder), and benzoyl peroxide (powder). Medium-sensitivity substances are the modem safety industrial explosives (slurry explosives, ammonium nitrate explosives), black powder, AIBN, and t-butyl-benzoate. Among low sensitivity substances are non-cap explosives dinitro benzene, dinitropentamethylenetetramine, ANFO, ammonium nitrate, nitromethane, dinitrotoluene, and cast TNT. 

On heating of sodium azide with benzofuroxans in ethylenglycole or DMSO the corresponding benzofurazans are formed [523, 525], If the reaction is carried out in a medium of acetic or iso-butyric acids, that is, actually using HN3, the nitrobenzofurazans sought are formed in good yield (Scheme 2.86) [526],... 

Thermolysis of 5-aminotetrazole above 200 °C gave hydrazoic acid (HN3), hydrazoniiun azide (H5N5), cyanamide and a polymer (CHsNs) and the reaction was sensitive to the medium used (72CI(L)294>. Thermal decomposition of explosive tetrazole-5-diazonium salts (102) has been used to generate carbon in the atomic state (74JA7830). 

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