Pyridine sulfuric anhydride

L-Pyroglutamyl-L-glutaminyl-L-aspartyl-L-tyrosine azide L-Threonyl-glycyl-L-tryptophanyl-L-methionyl-L-aspartyl-L-phenylalaninamide Pyridine sulfuric anhydride Sodium carbonate... 

Ethyl sulfate Flammable liquids Fluorine Formamide Freon 113 Glycerol Oxidizing materials, water Ammonium nitrate, chromic acid, the halogens, hydrogen peroxide, nitric acid Isolate from everything only lead and nickel resist prolonged attack Iodine, pyridine, sulfur trioxide Aluminum, barium, lithium, samarium, NaK alloy, titanium Acetic anhydride, hypochlorites, chromium(VI) oxide, perchlorates, alkali peroxides, sodium hydride... 

There are several methods reported in the literature for transforming vicinal diols into ct-diketones while avoiding the risk of C-C bond cleavage.26 Examples include the standard Swem conditions (dimethyl sulfoxide and oxalyl chloride followed by triethylamine), or the use of DMSO activated by acetic anhydride, pyridine-sulfur trioxide complex, or dicyclohexylcarbodiimide (Mq/J-att oxidation). Diones are also obtained by treatment with benzalacetone as a hydride acceptor in the presence of catalytic amounts of tris(triphenylphosphine)ruthenium dichlonde [(PPh RuCFl.27 Recent developments include the use of w-iodoxyben/.oic acid28 or the oxoammonium salt of 4-acctamidoletramethylpipcridine-1-oxyl and y -toluencNulfonic acid.29... 

Successively, 145 g (0.5 mole) of trimethoprime and 83 g (0.5 mole) of vanillin was added to 500 ml of pyridine, and about 130 g of sulfurous anhydride was added in three hours. The temperature of the reaction mixture rose spontaneously between 40° and 50°C from the start of the introduction and was held there until the end of the reaction. It was left for 24 hours at ordinary temperature. Then the reaction mixture was poured into a large volume of ether, the precipitate which appeared was filtered off and washed with ether. The crude product was then dispersed in water and treated with dilute sodium hydroxide to pH 9.30-9.40. A light insoluble substance was filtered off, then the product was reprecipitated by the addition of hydrochloric acid to the alkaline solution to pH 2-3. It was filtered, washed with water, and then with ethanol. After drying, (+/-)-a-[[4-amino-5-[(3,4,5-trimethoxyphenyl)methyl]-2-pyrimidinyl]amino]-3-ethoxy-4-hydroxybenzenemethanesulfonic acid, was obtained, melting point 145°C. TLC of the product gave a single spot. 

Food, flavors consist of numerous compounds, none of which alone is characteristic of specific food. Classes of compounds which emcompass food flavors are - hydrocarbons (aliphatic, ali-cyclic, aromatic) carbonyls (aldehydes, ketones) carboxylic acids, esters, imides, anhydrides alcohols, phenols, ethers alkylamines, alkylimines aliphatic sulfur compounds (thiols, mono-, di- and tri-sulfides) nitrogen heterocyclics (pyrroles, pyrazines, pyridines) sulfur heterocylics (thiophenes, thiazoles, trithiolane, thialidine) and oxygen-heterocyclics (lactone, pyrone, furan). Discussion will be limited to striking developments in heterocyclics. 

As noted at several points in previous sections, iodine-based reagents can act as Lewis acids. This has been known for many years, and has been exploited in the formation54 and cleavage55 of isopropylidene acetals of carbohydrates. In recent work, we have shown56 that iodine-acetic anhydride is an effective combination for the acetylation or partial acetylation of sugars this represents a practical alternative to the commonly used pyridine-acetic anhydride combination. The potential of iodine-based reagents to activate oxygen as well as sulfur centers is clear. 

REDUCTION, REAGENTS Bis(triphenyl-phosphine)copper tetrahydroborate. Borane-Pyridine. Calcium-Methylamine/ ethylenediaminc. Chlorobis(cyclopenta-dienyl)tetrahydroboratozirconium(IV). Chromium(II)-Amine complexes. Copper(0)-lsonitrile complexes. 2,2-Dihydroxy-l, 1-binaphthyl-Lithium aluminum hydride. Di-iododimethylsilane. Diisobutyl-aluminum 2,6-di-/-butylphenoxide. Diisobutyl aluminum hydride. Dimethyl sulfide-Trifluoroacetic anhydride. Disodium tetracarbonylferrate. Lithium-Ammonia. Lithium-Ethylenediamine. Lithium bronze. Lithium aluminum hydride. Lithium triethylborohydride. Potassium-Graphite. 1,3-Propanedithiol. Pyridine-Sulfur trioxide complex. 

In a typical example, 10 mmol of an alcohol, 11 mmol of oxalyl chloride, and 24 mmol of DMSO in 40 mL of dichloromethane react at -60 °C. The mixture is then made alkaline with 50 mmol of triethylamine [1023] (equation 262). In other instances, the molar ratios of the alcohol to DMSO and to the activator (benzoic anhydride) were 1 47 and 1 17, respectively with phosphorus pentoxide as the activator, the respective molar ratios were 1 47 and 1 1 [1009], and with pyridine-sulfur trioxide, they were 1 70 and 1 3 [1018]. Dichloromethane and toluene [1012] are the best solvents. 

Furansulfonic acid176 provides an example Pure furan, b.p. 31.2-31.5°, is prepared from technical furan by way of the maleic anhydride adduct, which is then decomposed at 140 to 150°. This furan is treated with the pyridine-sulfur trioxide adduct in a bomb-tube for 8-10 h at 100°. This product is treated with a paste of barium carbonate in water for 30-40 min, then filtered hot, and concentrated, and the barium sulfonate is precipitated by ethanol. The following yields are obtained from 1.9 g of furan with 4.4 g of pyridine-sulfur trioxide 30%, with 8.8 g 56%, and with 13.4 g 90%, S-Benzylthiouronium 2-furansulfonate melts at 205°. 

Various reaction conditions and times have been employed for both acetylation and depolymerization. Acetylation has been performed with pyridine/acetic anhydride for 8 h at 100°C (Kocourek and Ballou, 1969), two days at room temperature (Kooiman, 1961), a combination of ambient and high temperatures (O Neill and Selvendran, 1983) or with the inclusion of dimethyl formamide (Stewart et al., 1968). The xyloglucan from the cell walls of runner bean was acetylated with acetic anhydride-pyridine (1 1 v/v) for 12 h at 20°C followed by 8 h at 100°C (O Neill and Selvendran, 1983). Acetolysis has been carried out in glacial acetic acid/ acetic anhydride/concentrated sulfuric acid (1 1 0.1 v/v) for 13 h at 40°C (Kocourek and Ballou, 1969) or with acetic anhydride/concentrated sulfuric acid for 1 h at 0 C followed by two weeks at 50°C (Kooiman, 1961). Acetolysis of the acetylated xyloglucan derived from runner bean cell walls was performed with acetic anhydride-glacial acetic acidconcentrated sulfuric acid (1 1 0.1 v/v) for 12 h at 37°C, and a number of fragments was characterized (O Neill and Selvendran, 1983). For a discussion of the relative merits of the different procedures for acetolysis, the reader should consult Stewart et al. (1968). 

This bisfnaphthalic anhydride) was prepared from acenaphthene derivative-4,4 -diacenaphthyl sulfone, which was synthesized by the interaction of acenaphthene with a mixture of dimethybulfate and sulfuric anhydride [94] or chlorosulfonic acid [95]. Sulfone-bis-(4,5-dicarboxynaphthyl l) dianhydride results from oxidation of bis-acenaphthyl with potassium permanganate in pyridine [94] ... 

Other oxidation reactions using DMSO as an oxidant include the Pfitzner-Moffatt Oxidation (DMSO/dicyclohexylcarbodiimide), Swem oxidation (DMSO/oxalyl chloride or trifluoroacetic anhydride), Onodera oxidation (DMSO/phosphorus pentoxide), Parikh-Doering Oxidation (DMSO/pyridine-sulfur trioxide), Corey-Kim Oxidation (dimethyl sulfide/Ai-chlorosuccinimide), and Liu oxidation (DMSO/phenyl dichlorophosphate). 

In view of its constitution, Alizarin Blue (I) might be expected to display the characteristics of alizarin (page 96) and 8-hydroxyquinoline (page 335). This is not the case, as shown by the facts that it is neither soluble in alkali as is alizarin nor in dilute acids as is oxine. Probably Alizarin Blue is a chelate compound as represented in (la). Solutions can be prepared in dioxane, pyridine, acetic anhydride, concentrated sulfuric acid. These solutions react with strongly acid solutions of copper salts to produce a com-flower-blue crystalline precipitate, whose constitution as an inner complex compound is shown in (II). 

Acetamido derivatives were prepared as described in Section 7.7.8 with the pyridine-sulfur trioxide complex replaced by acetic anhydride. The following procedure was used for the other amides. 

Precursors of imidazoquinoxalines-compounds 109a, b and 112-have been synthesized from chloroquinoxalines 128 and corresponding amines in the presence of EtsN. To oxidize aminoalcohols 112 to ketones 114, different oxidative systems have been used a complex of trimethylamine and sulfuric anhydride in DMSO, chromium(VI) oxide in pyridine (Sarett method) (Luzzio 1998 Caamano et al. 2000), and dichloroxalate in DMSO (Swern method) (Scheme 4.58) (Ohmori et al. 1997 Parra et al. 2001 Deleuze-Masqudfa et al. 2004). 

Chromic(VI) acid Acetic acid, acetic anhydride, acetone, alcohols, alkali metals, ammonia, dimethylformamide, camphor, glycerol, hydrogen sulflde, phosphorus, pyridine, selenium, sulfur, turpentine, flammable liquids in general... 

Perchloric acid Acetic acid, acetic anhydride, alcohols, antimony compounds, azo pigments, bismuth and its alloys, methanol, carbonaceous materials, carbon tetrachloride, cellulose, dehydrating agents, diethyl ether, glycols and glycolethers, HCl, HI, hypophosphites, ketones, nitric acid, pyridine, steel, sulfoxides, sulfuric acid... 

Pyridine Chlorosulfonic acid, chromium trioxide, formamide, maleic anhydride, nitric acid, oleum, perchromates, silver perchlorate, sulfuric acid... 

Bisa.codyl, 4,4 -(2-PyridyLmethylene)bisphenol diacetate [603-50-9] (Dulcolax) (9) is a white to off-white crystalline powder ia which particles of 50 p.m dia predominate. It is very soluble ia water, freely soluble ia chloroform and alcohol, soluble ia methanol and ben2ene, and slightly soluble ia diethyl ether. Bisacodyl may be prepared from 2-pyridine-carboxaldehyde by condensation with phenol and the aid of a dehydrant such as sulfuric acid. The resulting 4,4 -(pyridyLmethylene)diphenol is esterified by treatment with acetic anhydride and anhydrous sodium acetate. Crystallisation is from ethanol. 

Production is by the acetylation of 4-aminophenol. This can be achieved with acetic acid and acetic anhydride at 80°C (191), with acetic acid anhydride in pyridine at 100°C (192), with acetyl chloride and pyridine in toluene at 60°C (193), or by the action of ketene in alcohoHc suspension. 4-Hydroxyacetanihde also may be synthesized directiy from 4-nitrophenol The available reduction—acetylation systems include tin with acetic acid, hydrogenation over Pd—C in acetic anhydride, and hydrogenation over platinum in acetic acid (194,195). Other routes include rearrangement of 4-hydroxyacetophenone hydrazone with sodium nitrite in sulfuric acid and the electrolytic hydroxylation of acetanilide [103-84-4] (196). 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

By a suitable choice of activating reagents, primary and secondary alcohols can be selectively oxidi2ed to carbonyl compounds in good yields at room temperatures. Typical activating reagents are acetic anhydride, sulfur trioxide—pyridine, dicyclohexyl carbodiimide, and phosphoms pentoxide (40). 

Pyridazines with an appropriate side chain attached to the sulfur atom at position 3 can be transformed into bicyclic systems. For example, pyridazinyl /3-ketoalkyl sulfides are cyclodehydrated in sulfuric acid to give thiazolopyridazinium salts, and 3-carboxymethyl-thiopyridazines are transformed by acetic anhydride in pyridine into 3-hydroxythiazolo[3,2-6]pyridazinium anhydro salts (Scheme 52). 

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