Polyphosphoric acid catalyst

Eleven 50-ml beakers was charged with L-aspartic acid (0.01 mol) and solubilized with 13.3 ml of IM hydrochloric acid (0.013 mol) at ambient temperature. The first three beakers were treated with 0.066 ml of polyphosphoric acid (specific gravity 2.0) and then warmed to 80°C acid. The second three beakers was treated with 0.266 ml polyphosphoric acid the last four beakers were treated with 0.399 g of polyphosphoric acid. Each solution was dried at 120°C, resulting in clear glassy pucks of intimate mixtures of aspartic acid and the polyphosphoric acid catalyst. The dried materials... 

The synthesis of 2,4-dihydroxyacetophenone [89-84-9] (21) by acylation reactions of resorcinol has been extensively studied. The reaction is performed using acetic anhydride (104), acetyl chloride (105), or acetic acid (106). The esterification of resorcinol by acetic anhydride followed by the isomerization of the diacetate intermediate has also been described in the presence of zinc chloride (107). Alkylation of resorcinol can be carried out using ethers (108), olefins (109), or alcohols (110). The catalysts which are generally used include sulfuric acid, phosphoric and polyphosphoric acids, acidic resins, or aluminum and iron derivatives. 2-Chlororesorcinol [6201-65-1] (22) is obtained by a sulfonation—chloration—desulfonation technique (111). 1,2,4-Trihydroxybenzene [533-73-3] (23) is obtained by hydroxylation of resorcinol using hydrogen peroxide (112) or peracids (113). 

Polyphosphoric acid supported on diatomaceous earth (p. 342) is a petrochemicals catalyst for the polymerization, alkylation, dehydrogenation, and low-temperature isomerization of hydrocarbons. Phosphoric acid is also used in the production of activated carbon (p. 274). In addition to its massive use in the fertilizer industry (p. 524) free phosphoric acid can be used as a stabilizer for clay soils small additions of H3PO4 under moist conditions gradually leach out A1 and Fe from the clay and these form polymeric phosphates which bind the clay particles together. An allied though more refined use is in the setting of dental cements. 

As basic catalysts KOH, NaOH or piperidine are used. As acidic catalysts are used HCl, H2SO4, polyphosphoric acid or /j-toluenesulfonic acid. 

Polyphosphoric acid is a commonly used catalyst for this reaction however, in some cases a mixture of hydrogen bromide/acetic acid gives better results. Acylation of the S-phenyl-, V-(4-tolyl)- or S-(l-naphthyl)-substituted thiobenzenepyruvic acids 3a-c affords the corresponding dibenzo[A,/]thiepins in satisfactory yields, while reaction of the S-(4-methoxyphenyl) or S-(2-naphthyl) derivatives fails to provide any thiepin.60 The intramolecular Friedel-Crafts acylation of 2-(arylsulfanyl)benzeneacetic acids also yields the corrresponding dibenzothiepins in this case the use of hydrogen fluoride sometimes results in purer products.38 The applicability of this method is restricted to the synthesis of stable bisannulated thiepins. 

Sulfonic acid catalysts can also be used to prepare poly(arylene ether sulfone)s, such as (CF3C0)20, polyphosphoric acid (PPA),26 MeS03H-P205 mixture,33 and CF3SO3H.34... 

Ion 21 can either lose a proton or combine with chloride ion. If it loses a proton, the product is an unsaturated ketone the mechanism is similar to the tetrahedral mechanism of Chapter 10, but with the charges reversed. If it combines with chloride, the product is a 3-halo ketone, which can be isolated, so that the result is addition to the double bond (see 15-45). On the other hand, the p-halo ketone may, under the conditions of the reaction, lose HCl to give the unsaturated ketone, this time by an addition-elimination mechanism. In the case of unsymmetrical alkenes, the attacking ion prefers the position at which there are more hydrogens, following Markovnikov s rule (p. 984). Anhydrides and carboxylic acids (the latter with a proton acid such as anhydrous HF, H2SO4, or polyphosphoric acid as a catalyst) are sometimes used instead of acyl halides. With some substrates and catalysts double-bond migrations are occasionally encountered so that, for example, when 1 -methylcyclohexene was acylated with acetic anhydride and zinc chloride, the major product was 6-acetyl-1-methylcyclohexene. ... 

More recent studies (4,10) have shown that various acids and organometallic compounds can serve as catalysts for the preparation of II. The advantages include lower polymerization temperatures, higher yields, lower molecular weights, and the use of conventional large scale equipment. Examples include bulk polymerizations using H 0 (11), Et Al Cl (12), CrCl,.6H 0 (13), (C,H 0) P0-BC1, (14 , polyphosphoric acid... 

The most widely used route to l-benzazepin-2-ones involves the Beckmann or Schmidt reaction of the easily accessible 1-tetralones. Many biologically active compounds described in this review have been prepared on the basis of these reactions they have been fully reviewed [2], In the Beckmann reaction of 1-tetralone oximes, polyphosphoric acid is used as a catalyst-solvent in most instances. Aryl migration generally takes precedence over alkyl migration under these reaction conditions, and various 1-tetralone oximes substituted on the aromatic and/or aliphatic rings can be converted to the appropriate 2,3,4,5-tetrahydro-l//-l-benzazepin-2-ones (51) [5, 20-23, 36, 59, 65, 80, 107-112]. Both courses of the rearrangement occur in some instances, yielding l-benzazepin-2-ones (51) and the isomeric 2-benzazepine-l-ones, probably due to electronic effects of the substituents [90, 113, 114]. 

Diaryl sulfones can be formed by treatment of aromatic compounds with aryl sulfonyl chlorides and a Friedel-Crafts catalyst.167 This reaction is analogous to Friedel-Crafts acylation with carboxylic acid halides (1-14). In a better procedure, the aromatic compound is treated with an aryl sulfonic acid and P205 in polyphosphoric acid.168 Still another method uses an arylsulfonic trifiuoromethanesulfonic anhydride ArS020S02CF3 (generated in situ from ArS02Br and CF3S03Ag) without a catalyst.169... 

A variety of both protic and Lewis acids have been used to effect Fischer cyclizations. Hydrochloric acid or sulfuric acid in aqueous, alcohol or acetic acid solution are frequently used. Polyphosphoric acid and BF3 in acetic acid have also been employed[10]. Zinc chloride is the most frequently used of the common Lewis acids. This choice is supported by comparative studies with FeCI3, AICI3, CoCI2 and NiCl2, which found ZnCl2 to be the most effective catalyst[l 1]. Zinc chloride can be used either as a solid mixture with the hydrazone reactant or in ethanol or acetic acid solution[12]. 

Alkylation. Friedel-Crafts alkylation (qv) of benzene with ethylene or propylene to produce ethylbenzene [100-41 -4], CgH10, or isopropylbenzene [98-82-8], C9H12 (cumene) is readily accomplished in the liquid or vapor phase with various catalysts such as BF3 (22), aluminum chloride, or supported polyphosphoric acid. The oldest method of alkylation employs the liquid-phase reaction of benzene with anhydrous aluminum chloride and ethylene (23). Ethylbenzene is produced commercially almost entirely for styrene manufacture. Cumene [98-82-8] is catalytically oxidized to cumene hydroperoxide, which is used to manufacture phenol and acetone. Benzene is also alkylated with C1Q—C20 linear alkenes to produce linear alkyl aromatics. Sulfonation of these compounds produces linear alkane sulfonates (LAS) which are used as biodegradable deteigents. 

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