Pyridine, reactions with—continued sodium

The stream of dry air is continued for about six hours or until most of the hydrogen chloride has been expelled and then another 55 grams of thionyl chloride is added. The reaction mixture is allowed to stand twenty-four hours, a few drops of pyridine are added and the mixture heated 4 hours on the steam bath. The cooled reaction mixture is poured into water, the crude product is washed with dilute sodium bicarbonate solution and finally taken up in benzene. The benzene is distilled at ordinary pressure and the residue distilled in vacuo to yield 60-70% of Tphenoxy-2-chloropropane, BP 93°-94°C/5 mm. 

Another useful chain reaction involves the PTOC (pyridine-2-thione-N-oxycarbonyl) esters developed by Barton. Reaction of a carboxylic acid chloride (RCOCl) with the sodium salt on N-hydroxypyridine-2-thione produces an ester designated as R-PTOC. Addition of radical Y" (formed by an earUer initiation step) to the R-PTOC leads to the carboxy radical RCOj. The carboxy radical then decarboxylates to produce the radical R, which can continue the chain reaction or can undergo other reactions. 

A solution of 7.2 g of sodium borohydride (analyzing at 87 % purity) in 300 ml of pyridine is added dropwise, with vigorous stirring, over 7 hr to a solution of 50 g of pregnane-3,11,20-trione in 100 ml of pyridine and 18 ml of water. The temperature is kept at 18-20°. The stirring at this temperature is continued for another 2 hr, after which the reaction mixture is poured slowly into dilute hydrochloric acid (575 ml of cone hydrochloric acid in 5.2 liters of water) and the stirring continued for 1 hr. The precipitate is filtered, washed with... 

To a stirred solution of 120 ml of methylene chloride, 18 ml of dry pyridine, and 5 ml of iodine pentafluoride maintained at —10°C to —20°C in a Dry Ice-carbon tetrachloride slurry is added a solution of 13.5 gm (0.1 mole) of cumyl-amine in 10 ml of methylene chloride over a 1 hr period. The reaction mixture is stirred for another hour at —10°C, and then for 1 hr at 0°. After this time, water is added to the reaction mixture and stirring is continued until the yellow solid which had formed is dissolved. The lower organic layer is separated and washed in turn with water, 1 N hydrochloric acid, a saturated sodium thiosulfate solution, and again with water. After drying with anhydrous magnesium sulfate and filtration, the product solution is partially evaporated by means of a rotary evaporator at a temperature below 30°C. The brown solid obtained on cooling is separated and recrystallized twice from methylene chloride yield 4.75 gm (17.9%), m.p. 86.9°-88.7°C. 

A 100-mL, two-neck, round-bottom flask, equipped with two addition funnels was charged with pyridine (0.43 mL, 5.3 mmol) and 20 mL of methylene chloride. A solution of triflic anhydride (0.86 mL, 5.11 mmol) dissolved in 10 mL of methylene chloride was placed in one addition funnel. The sugar (2.55 mmol) dissolved in 10 mL of methylene chloride was placed in the other addition funnel. The flask was cooled to - 10°C in an ice-acetone bath, and the triflic anhydride solution added drop wise. A thick white precipitate began to form during die addition. After addition was complete, the suspension was allowed to stir for an additional 10 min. The sugar solution was added drop wise and stirring continued for an additional 1.5 h. The reaction mixture was poured into 50 mL of ice water, die layers were separated, and the aqueous layer was extracted with two 50-mL portions of methylene chloride. The combined extracts were dried over sodium sulfate, and the solvent was removed in vacuo. Hexane extraction, followed by in vacuo solvent removal, gave the Inflate ester [10]. 

To a stirred suspension of 4.6 g (13.8 mmoles) of the (S)-3-(2-hydroxyethyl)-5-(2-oxo-l,3-oxazolidin-4- ylmethyl)-lH-indol-2-carboxylic acid ethyl ester in 42 ml of dichloromethane were added 4.2 ml of pyridine, 3.9 g (20.7 mmoles) oftosyl chloride and 170 mg (1.38 mmoles) of dimethylaminopyridine and the stirring continued at room temperature for 20 hours. The reaction mixture was poured over 20 ml of 3 N, HCI precooled to 0°C and extracted twice with dichlormethane. The organic phases were washed with brine, dried on anhydrous sodium sulphate and the solvent evaporated to dryness. The evaporated solid was crystallised with isopropyl alcohol to give 6.4 g (95%) of the title compound as a white crystalline solid. Melting point 166.4°-168.2°C. 

Work performed in our laboratory over the last several years has systematically addressed many of the problems associated with the thiocyanate chemistry. The use of sodium or potassium trimethylsilanolate for the cleavage reaction provided a method for rapid and specific hydrolysis of the derivatized C-terminal amino acid, which left the shortened peptide with a free C-terminal carboxylate ready for continued rounds of sequencing (3). The use of diphenylphosphoroisothiocyanatidate (DPP-ITC) and pyridine combined the activation and derivatization steps and... 

The chemical scheme for C-terminal sequencing is shown in Figure 2. The first step involves treatment of the peptide or protein sample with diisopropylethylamine in order to convert the C-terminal carboxylic acid into a carboxylate salt. Derivatization of the C-terminal amino acid to a thiohydantoin is accomplished with diphenylisothiocyanatidate (liquid phase) and pyridine (gas phase). The peptide is then extensively washed with ethyl acetate and acetonitrile to remove reaction by-products. The peptide is then treated briefly with gas phase trifluoroacetic acid, followed by water vapor in case the C-terminal residue is a proline (this treatment has no effect on residues which are not proline). The derivatized amino acid is then specifically cleaved with sodium or potassium trimethylsilanolate to generate a shortened peptide or protein which is ready for continued sequencing. In the case of a C-terminal proline which was already removed by water vapor, the silanolate treatment merely converts the C-terminal carboxylic acid group on the shortened peptide to a carboxylate. The thiohydantoin amino acid is then quantitated and identified by reverse-phase HPLC. 

Place 1 g of salicylic acid in each of four 13 x 100-mm test tubes and add to eachtube2 mL of acetic anhydride. To the first tube addO.2 gof anhydrous sodium acetate, note the time, stir with a thermometer, and record the time required for a 4°C rise in temperature. Replace the thermometer and continue to stir occasionally while starting the next acetylation. Obtain a clean thermometer, put it in the second tube, add 5 drops of pyridine, observe as before, and compare with the first results. To the third and fourth tubes add 5 drops of boron trifluoride etherate and 5 drops of concentrated sulfuric acid, respectively. What is the order of activity of the four catalysts as judged by the rates of the reactions ... 

The spectroscopic probe pyridine-N-oxide was used to characterize polar microdomains in reverse micelles in supercritical ethane from 50 to 300 bar. For both anionic and nonionic surfactants, the polarities of these microdomains were adjusted continuously over a wide range using modest pressure changes. The solubilization of water in the micelles increases significantly with the addition of the cosolvent octane or the co-surfactant octanol. Quantitative solubilities are reported for the first time for hydrophiles in reverse micelles in supercritical fluids. The amino acid tryptophan has been solubilized in ethane at the 0.1 wt.% level with the use of an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (AOT). The existence of polar microdomains in aggregates in supercritical fluids at relatively low pressures, along with the adjustability of these domains with pressure, presents new possibilities for separation and reaction processes involving hydrophilic substances. 

To a stirred pyridine solution (30 mL) of benzenetetracarbonyl tetrachloride (5.5 g, 17 mmol), prepared from benzenetetracarboxylic anhydride and phosphorous penta-chloride, was added portionwise (-)-bomeol (10.3 g, 67 mmol) at 0 °C, and stirring was continued for 18 h under a nitrogen atmosphere. The reaction mixture was then poured into a mixture of 6% aqueous hydrogen chloride (150 mL) at 5 °C (ice bath) and extracted with three portions of ether (200 mL). The combined organic extracts were washed with saturated aqueous sodium bicarbonate and brine, dried over magnesium sulfate, and then evaporated to dryness under a reduced pressure. The crude product obtained was purified by repeated recrystallization from methanol and then twice from hexane to yield pure (-)-tetrabornyl 1,2,4,5-benzenetetracarboxylate (8.0 g, 60%), mp 239.5 - 241.0 °C, [a]p = -59.5° (0.9, benzene). 

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