Polyphosphoric add

Substituted phenacyl anthranilates were prepared by reaction of sodium anthranilate with substituted phenacyl halides in DMF. The phenacyl esters were cyclized in polyphosphoric add or by heating to give the respective substituted 2-aryl-3-hydroxyquinoline-4(l. -ones in high yield <95CCC(60)1357>. 

Polyphosphoric add in cyclization of ethyl a-acetyl-/3-(2,3-dimethoxy-phenyl)propionate to 6,7-dimeth-oxy-3-methylindene-2-carboxyl-ate, 40,43... 

One of the most reliable methods for constructing the oxazole ring is the cyclodehydration of a-acylamino ketones, the Robinson-Gabriel synthesis (1909/1910) (equation 93). The reaction is usually conducted in the presence of sulfuric add or phosphorus pentachloride and more recently polyphosphoric add, phosgene or anhydrous hydrogen fluoride have... 

The metioD takes place in the presence of an add catafyst. The materials proposed for this include Dow 50 X 12 resins, polyphosphoric adds, both solid or deposited on kieselguhr, metallic o.xides or alumina with a spedfle surface area of 200 m /g. These systems operate with a MiSV approaching 1 once-through conversions are as high as... 

One final interesting preparation of this ring system involves the reaction of the tetrazolo[l,5-6]pyridazine (174) with polyphosphoric add to give 7-azido-4f/-pyrimido[l,2-6]pyridazin-4-one (175). This reaction involves azido-tetrazolo valence isomerization, which has been studied in other heterocyclic systems (71JHC1055). 

Anthrone forms in polyphosphoric add a polycondensate 117 having semiconducting and paramagnetic properties. Compound 117 was tested as thermo-and photostabilizer of PS. It was concluded [149] that the antioxidant properties are due to the ability of 117 to form CTC with R and ROj radicals. 

Cyclodehydration Aluminum chloride see also Methyl fluorene-9-carboxylate). Dowtherm. Fluorosulfonic acid. Hydrogen fluoride. Perchloric add. Phosphorus pentoxide. Phosphoryl chloride. Polyphosphate ester. Polyphosphoric add. Potassium bisulfate. Sodium aluminum chloride. Sulfur trioxide-Dimelhylformamide. />-Toluenesulfonic acid. Trifluoroacetic acid. Trifluoroacetic anhydride. 

N-Formylation of 2-aminobenzothiazoles is achieved by treatment with 7V-phenyl formamide and two equivalents of benzenesulfonyl chloride in pyridine as a solvent <88CCC3ii>. Condensation of 2-aminobenzothiazole with dimethylacetylendicarboxylate in ethanol affords pyrimido-benzo-thiazolones (172). Similar heterocyclic systems are obtained when 2-aminobenzothiazoles are treated with ethylbenzoyl acetate in polyphosphoric add (Scheme 42) <88jhC949>. 

Keto ester (33) was discussed in Chapter 19. The final cyclisation was carried out on the free acid (34) using polyphosphoric add (PPA), a powerful dehydrating agent. 

These sorts of compounds may look rather difficult to come by, but some simple ones are readily made. Cyciization of this keto-acid with polyphosphoric add leads to a sptrocycUc diketone. The spiw compound is formed because the more substituted enol is preferred in add solution. 

This material is an inorganic salt of polyphosphoric add and ammonia with the general structure [NH4P03] . There are two main families of ammonium polyphosphate as shown below ... 

APP is a stable, nonvolatile material. It slowly hydrolyzes in contact with water to produce monoammonium phosphate (orthophosphate). This process is autocatalytic and is accelerated by higher temperatures and prolonged exposure to water. The decomposition temperature of APP is related to the length of the polymer chain. Long-chain APP starts to decompose at temperatures above 300 °C to polyphosphoric add and ammonia. Short-chain APP, defined as that having a chain length below 100 monomer units, begins to decompose at temperatures above 150°C. 

On heating with polyphosphoric add o-haloacetoacetanilides give mixtures of 4-hydroxyquinaldines and 3-arylcarbamyl-2,6-dimethyl-4-pyrones (Xn-245 R = 2-C1C H4,2,4-Cl2C H3. 2,5-Cl2C6H3. 2-BrC6H4). The 4-pyrones (XU-245) are... 

Tilak and co-workers have continued their investigations on the synthesis of 2-ethoxycarbonyl-3-hydroxythiophanes, through the base-catalysed condensation of methyl vinyl ketone, chalcones, ethyl 2-benzoyl-acrylate, and Mannich bases with ethyl thioglycollate. Dehydration of the thiophanes with polyphosphoric add followed by dehydrogenation using chloranil or diphenyl disulphide affords thiophens. 

Evaluated Literature Data for the Polyphosphoric Add Equilibria Condusion 356 References 357... 

Westman, A.E.R. and Beatty, R. (1966) Equations for calculating chain length distributions in polyphosphoric adds and polyphosphate glasses. /. Am. 

Phosporus exists in the sea in the form of ions of (ortho) phosphoric acid, H3PO4. About 10% of the inorganic phosphate in seawater is present as PO4 and practically all the remaining phosphate exists as HPO4. The condensed phosphoric acids, L, diphosphoric acid, H4P2O7, and all polyphosphoric adds with P-O-P linkages, have so far not been detected in open seawaters but are known to occur in estuarine and coastal waters as a result of pollution with detergents. 

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