Polyphosphoric acid solvent

Additionally, the sequestering ability of polyphosphoric acid and phosphonic acid derivatives as well is a valuable property for their use as dispersants. The main task of dispersants is to suspend solid particles in water or organic solvents and avoid their coalescence and precipitation. This complex plays an important role in many processes and as a result dispersants are used in many technical fields. 

A powerful and efficient method for the preparation of poly(ketone)s is the direct polycondensation of dicarboxylic acids with aromatic compounds or of aromatic carboxylic acids using phosphorus pentoxide/methanesulfonic acid (PPMA)16 or polyphosphoric acid (PPA)17 as the condensing agent and solvent. By applying both of these reagents to the synthesis of hexafluoroisopropylidene-unit-containing aromatic poly(ketone)s, various types of poly(ketone)s such as poly(ether ketone) (11), poly(ketone) (12), poly(sulfide ketone) (13), and poly-... 

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]. 

The (3-lorm is obtained by dissolving crude quinacridone in any one of a variety of solvents (such as concentrated sulfuric acid/toluene or methylated sulfuric acid), followed by precipitation with water. The same end is achieved by dissolving the product in polyphosphoric acid, followed by rapid precipitation with ethanol at 45°C. The (3-product, however, is not pure and usually contains some a-crystal modification as well. 

KI (8.0 g, 48 mmol) and TBA-I (0.58 g, 1.5 mmol) are added to the sulphonic acid (6 mmol) and ethyl polyphosphate or polyphosphoric acid (48 mmol) [or P4O 0 (36 mmol)] in the appropriate solvent (20 ml) (CHC13 for ethyl polyphosphate sulpholane for polyphosphoric acid MeCN for P4O10) and stirred under reflux for ca. 5 h. H20 (10 ml) is added and the mixture is refluxed for a further 1 h and then poured into PhH (100 ml). The organic phase is separated, washed with H20 (3 x 50 ml) and aqueous Na2S203 (0.5M, 2 x 100 ml), dried (Na2S04), and evaporated to yield the disulphide. 

Considerable efforts have centered on carrying out the synthesis of polybenzimidazoles at more moderate temperatures. Polymerization of the isophthalic acid or its diphenyl ester have been successfully carried out in polyphosphoric acid or methanesulfonic acid-phosphorous pentoxide at 140-180°C, but the reaction is limited by the very low solubilities (<5%) of the reactants in that solvent. The lower reaction temperature is a consequence of activation of the carboxyl reactant via phosphorylation. Lower reaction temperatures are also achieved in hot molten nonsolvents such as sulfolane and diphenyl sulfone, but the need to remove such solvents by a filtration or solvent extraction is a disadvantage. 

Arylsulfonation of perimidines 78 (R = H or CF3) has been carried out in polyphosphoric acid and found to occur at the 6(7)- and 4(9)-positions. Separation of the product sulfones 79 and 80 was easily achieved due to their different chromatographic mobilities. The 4(9)-isomers 79 are more mobile due to the intramolecular hydrogen bond and, in low-polarity solvents, exist virtually completely as the 9-tautomer <2002CHE1084>. 

Reaction of succinic anhydride with benzene in the presence of anhydrous aluminium chloride (slightly over two equivalents see above) yields 3-benzoylpropanoic acid. This may be reduced by the Clemmensen method in the presence of a solvent (toluene) immiscible with the hydrochloric acid to 4-phenylbutanoic acid. Cyclisation to a-tetralone (Expt 6.123) is then effected smoothly by treatment with hot polyphosphoric acid. This reaction sequence represents the first stages in the Haworth procedure for the synthesis of polycyclic aromatic hydrocarbons (see Section 6.1.4, p. 839). 

Only resinous products and methyl 6-acetamidopyridine-3-carboxylate were obtained when methyl 6-aminopyridine-3-carboxylate was reacted with ethyl 2-acetoxyacetoacetate by heating in phosphorus pentoxide, methanesulfonic acid, or polyphosphoric acid in the absence or presence of a solvent such as toluene, xylene, or methylene chloride. However the desired methyl 3-acetoxy-2-methyl-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-7-carboxylate 93 was obtained when the above components were reacted in N, A-dimethylacetamide in the presence of polyphosphoric acid at 100°C for 48 hours (84FES837). 

The amino benzopyran of step 5 (2.0 g) and dimethyl acetylene dicarboxylate (1.24 g 1.01 ml) were refluxed in ethanol (30 ml) for 26 hours. The reaction mixture was cooled to 0°C and the insoluble yellow-brown solid was collected by filtration and washed with a little ethanol and dried to give 2.0 g of a product which was a mixture of maleic and fumaric esters obtained by Michael addition of the amine to the acetylene. This mixture of esters (2.0 g) was treated with polyphosphoric acid (30 ml) and heated on the steam bath with stirring for 20 minutes. The reaction mixture was then poured onto ice and stirred with ethyl acetate. The organic layer was separated, washed with water and dried. The solvent was evaporated to leave 1.6 g of a yellow orange solid. Recrystallisation of this solid from ethyl acetate gave the required product as fluffy orange needles, mp 187°-188°C. 

With another enolizable carfeonyl group in the molecule, cyclization may occur to give a new 1,3-dicarbonyl compound. Popular conditions for this reaction are polyphosphoric acid (PPA—partly dehydrated and polymerized H3PO4) in acetic acid as solvent. 

Carbodiimides in solvents such as DMSO or tetramethylurea can dehydrate H3P04, polyphosphoric acids, or ring acids to the bicyclic ultraphosphonic acid (H2P4On), as illustrated by the following reaction ... 

Nowadays, activities of nucleic acids are controlled by interactions of Mg, Ca or Zn, but also by heavy-metal ions or electrophilic agents with certain specific sequences (e.g. in induction of metallothionein). Though this does imply NAs to act as ligands in physiological conditions, it need not imply that they could achieve the above sequence of steps, let alone the problem that up to now not even a hint of a prebiotic NA synthesis pathway was demonstrated, not even when using polyphosphoric acid in organic solvents. The E (L) values for NAs, nucleoside triphosphates or simpler species such as glycerinaldehyde-2,3-diphosphate are way too low to permit the sequence of events on their own. 

Aromatic aUazines and ketazines. Polyphosphoric acid is an excellent catalyst and solvent for production of amines from aromatic aldehydes and ketones in the presence of various carbonyl reagents, for example, hydrazine, its salts, semicarbazide hydrochloride, toluene/i-sulfonohydrazide, and acid hydrazides. The reaction is usually complete at 100° within 15 min. The reaction is not useful in the case of aliphatic carbonyl compounds. 

Hydrofluoric acid (bp, 19.5°C Tc, 188°C Pc, 64 atm), nitrogen dioxide (bp, 21°C Tc, 158.2°C Pc, 100 atm in equilibrium with N2O4), sulfuric acid (decomposition at 280°C), and polyphosphoric acid are candidates for solvents in solvothermal reactions, and the reactions of these solvents will produce a variety of products that cannot be prepared by any other methods. For example, Bialowons et al. reported that solvothermal treatment of (02)2Ti7F3o in anhydrous HF at 300°C yielded single crystals of TiF4. Solvothermal reactions in these solvents may produce fruitful results and a new field seems to be awaiting many researchers. 

Most ketoximes will undergo the normal Beckmann rearrangement under the proper acidic or neutral conditions to yield an amide or a mixture of amides, and a wide variety of examples are listed in reviews. Polyphosphoric acid continues to be a common reagent for the Beckmann rearrangement. However, in view of the viscosity and utility in a large molar excess as a solvent, polyphosphoric acid has several drawbacks in the work-up step. A recent procedure suggests the use of xylene as a cosolvent. Under these conditions the reaction temperature is easily controlled and the yields are the same or better than those obtained in polyphosphoric acid alone. 

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