Pyridine hydrochloride

A. Heptoic anhydride enanthic anhydride). In a 250-ml. round-bottomed three-necked flask, equipped with a stirrer, dropping funnel, and thermometer, are placed 15.8 g. (16.1 ml., 0.2 mole) of dry pyridine (Note 1) and 25 ml. of dry benzene (Note 2). I hen 14.8 g. (15.5 ml., 0.1 mole) of heptoyl chloride (Note 3) is added rapidly to the stirred solution. The temperature rises only slightly, and a pyridinium complex separates. While stirring is continued, 13.0 g. (14.1 ml., 0.1 mole) of heptoic acid (Note 3) is added from the dropping funnel over a period of 5 minutes. The temperature rises rapidly to 50-65° (Note 4), and pyridine hydrochloride is formed. After stirring for 10 minutes, the solid is collected on a chilled Buchner funnel and washed twice with 25-ml. portions of dry benzene (Note 5). 

Pyridine hydrochloride is hygroscopic the filtration should be done rapidly, using a Buchner funnel. 

Chloromethyl)pyridine hydrochloride [1822-51-1] M 164.0, m 170-175°, 172-173°, pK , -5.6. Purified by recrystn from EtOH or EtOH-dry Et20. It melts between 171° and 175° and the clear melt resolidifies on further heating at 190° and turns red to black at 280° but does not melt again. The picrate-hydrochloride (prepared in EtOH) has m 146-147°. The free base is an oil, [Mosher and Tessieri J Am Chem Soc 73 4925 1951.]... 

Pyridine hydrochloride [628-13-7] and washed with diethyl ether. 

Typically in such a process the bis-phenol A is dissolved in about ten times its weight of pyridine and vigorously stirred at 25-35°C. Phosgene is then bubbled into the solution and in a few minutes the pyridine hydrochloride starts to precipitate. As polymer is formed the viscosity of the solution increases and eventually becomes too great for stirring. The polymer is then recovered by the addition of a solvent such as methyl alcohol which dissolves the pyridine hydrochloride but precipitates the polymer. 

The striking effect of the catalyst is exemplified by the reaction of pregna-4, 16-diene-3,20-dione (10) with benzyl mercaptan. In the presence of piperidine only conjugate addition occurs to give (11) whereas with pyridine hydrochloride only the 3-benzyl thioenol ether (12) is formed. In the presence of p-toluenesulphonic acid both reactions take place to yield (13). 

The A" -3-keto group can be selectively protected as a thioenol ether in the presence of a 17- or 20-ketone. High yields are obtained with benzyl mercaptan and pyridine hydrochloride as a catalyst. 

Reaction of the potassium salt of salicylaldehyde with chlo-roacetone affords first the corresponding phenolic ether aldol cyclization of the aldehyde with the ketonic side chain affords the benzofuran (1). Reduction of the carbonyl group by means of the Wolf-Kischner reaction affords 2-ethyl-benzofuran. Friedel-Crafts acylation with anisoyl chloride proceeds on the remaining unsubstituted position on the furan ring (2). The methyl ether is then cleaved by means of pyridine hydrochloride (3). lodina-tion of the phenol is accomplished by means of an alkaline solution of iodine and potassium iodide. There is thus obtained benziodarone (4)... 

Hydrocortisone (25 g) and Bendazac chloride (21 g) are suspended in anhydrous dioxane (250 ml). Pyridine (6 ml) is added and the solution is kept under stirring for 2 hours at room temperature, Pyridine hydrochloride which separates is filtered and the clear dioxane solution is added, under strong stirring, to a solution of sodium bicarbonate (20 g) in distilled water (2,500 ml). The colorless precipitate which is formed is filtered, washed with water and dried on a porous plate. The substance crystallizes from ethanol. Needles. MP 174°-176 t Yield 75%. 

The mixture was cooled to 7°C, extracted with two 500-oc portions of ice water to remove pyridine hydrochloride, and the benzene solution of 3-o-methoxyphenoxy-2-hy-droxypropyl chlorocarbonate was added to 500 ml of cold concentrated ammonium hydroxide. The mixture was vigorously stirred at 5°C for 6 hours, then the crude white precipitate of 3-o-methoxyphenoxy-2-hydroxypropyl carbamate was filtered off, dissolved in 1,500 ml of hot benzene and completely dried by codistillation of last traces of water with benzene, treated with decolorizing carbon and filtered while hot. On cooling 160 g of product crystallized as white needles melting at 88° to 90°C. 

The combined liquors, which comprise an aqueous hydrochloric acid solution of 3-amino-methyl-pyridine hydrochloride, are then heated to a temperature of 60° to 65°C, and ethyl nitrite gas is passed into the heated solution. The ethyl nitrite is generated by placing 20 liters of 90% ethyl alcohol in a suitable vessel, diluting with 200 liters of water, and, while stirring, adding to the dilute alcohol 18.3 kg of nitrosyl chloride at the rate of 2.25 kg per hour. (The process using methyl nitrite is carried out by substituting a stoichiometrically equivalent quantity of methyl alcohol for the ethyl alcohol.)... 

A solution of 2 grams of A -19-norandrosten-3,17-dione and 0.4 gram of pyridine hydrochloride in 50 cc of benzene free of thiophene was made free of moisture by distilling a small portion 4 cc of absolute alcohol and 4 cc of ethyl orthoformate were added and the mixture was refluxed during 3 hours. 5 cc of the mixture were then distilled and after adding an additional 4 cc of ethyl orthoformate the refluxing was continued for 2 hours longer. The mixture was evaporated to dryness under vacuum and the residue was taken up in ether, washed, dried and evaporated to dryness. The residue was crystallized from... 

After filtration and recrystallization from ethanol, there are obtained 5-(2-chlorobenzyl)-4,5,6,7-tetrahydrothieno[3,2-cl -pyridine hydrochloride crystals (yield 60%) having a melting point (Koefler block) of 190°C. 

Step B A solution of the 3-tert-butylamino-2-oxopropanol in a mixture of pyridine hydrochloride and pyridine is treated with p-toluenesulfonylchloride. The mixture is stirred for /i hour at 25° to 30°C and then poured into cold water. The solution is treated with potassium carbonate and the pyridine evaporated in vacuo at a temperature between 55° and 60°C. The aqueous residue is treated with potassium carbonate and the mixture extracted with methylene chloride. Evaporation of the dried extract provides 1-toluene-sulfonyloxy-2-oxo-3-tert-butylaminopropane. 

A solution of 82 parts by weight of 7-chloromethyl-pyridine-hydrochloride in 60 parts of water is added dropwise, at 0 to 5°C, to 250 parts by weight of a 50% aqueous ethyl amine solution. The mixture is stirred for 1 hour at 60°C, whereupon it is cooled down and separated in the cold with solid potassium hydroxide. The oil formed is separated off, dried over potassium hydroxide and distilled. The ethyl-(7-picolyl)-amine formed boils over at 103° to 104°C under a pressure of 13 mm Hg. Its dihydrochloride melts at 198° to 200°C. 

A selective introduction of a chlorine atom at C-6 could be achieved (65) by treating 11 (and the / -anomer) with sulfuryl chloride in pyridine at — 70°C. followed by treatment of the resulting tetrachlorosulfate (83) with one mole of pyridine hydrochloride which gave 84. Heating of 84 with pyridine hydrochloride in chloroform resulted in further substitution by chloride to give 78 after dechlorosulfation. The above illustrated transformations support the proposed mechanism (65) for... 

The addition rate is about 30 drops/minute. After about half of the methanesulfonyl chloride has been added, white crystals of pyridine hydrochloride begin to precipitate, and the solution becomes viscous (Note 16). 

Aus der Mutterlauge erhalt man nach Zugabe von Salzsaure 0,0129 g (14% d.Th.) 3-Hydroxy-2-methvl-4,5-bis- hydroxymethyl]-pyridin-Hydrochlorid. 

The direct bromination of 2-hydroxypyridine is regioselective at C-3 whereas chlorination is not. Qu6guiner has developed a halide exchange reaction. Heating 3-bromo-2-hydroxypyridine in pyridine hydrochloride at reflux gives 3-chloro-2-hydroxypyridine in good yield <96TL(37)6695>. The directed aminomethylation of 3-hydroxy-2(lH)-pyridones and 3-hydroxy-4(lfl)-pyridones has been studied <96T(52)1835>. 

The presence of the base brings about the irreversible elimination of hydrogen chloride between the acid chloride and the acid the resulting pyridine hydrochloride precipitates out as the reaction progresses. 

Acidic treatment of prechilenine (139) (Section III,C) afforded the imino keto acid 377 via the imminium salt 140 (Scheme 68). Neutralization and work-up furnished the known y-lactol 371 in 90% overall yield from 139 (96, 181). Kondo et al. (183) obtained 139 from the epidioxide 122 by treatment with pyridine hydrochloride in pyridine along with 377 and norhydrastine. The acid 377 was converted to the known imino ester 373 through N,0-dimethylation. 

If N-succinimidyl chloroformate was used, filter out the white precipitate of 4-(dimethylamino) pyridine hydrochloride using a glass fiber filter pad. Collect the supernatant. 

There is nothing unusual about the acidic behavior of ammonium salts. In fact, any protonated amine can function as a proton donor. Because of this, many amine salts have been used as acids in synthetic reactions. If the chlorides are used, the amine salts are known as amine hydrochlorides. One of the earliest amine hydrochlorides studied with regard to its behavior as an acid is pyridine hydrochloride (pyridinium chloride), C5H5NH+C1. In the molten state, this compound undergoes many reactions of the type just shown. 

Many years ago, L. F. Audrieth studied numerous reactions of amine hydrochloride salts. These compounds contain a cation that is a protonated amine that can function as a proton donor. Consequently, the molten salts are acidic and they undergo many reactions in which they function as acids. This behavior is also characteristic of ammonium chloride as well as pyridine hydrochloride (or pyridinium... 

---