Phosphorus acid anhydrides zinc chloride

Phenyl cinnamate and other phenolic esters have been prepared by heating the acid and phenol in the presence of phosphorus oxychloride,1 and by heating the acid anhydride and phenol together in the presence of a dehydrating agent such as fused zinc chloride or anhydrous sodium acetate.2 Phenyl cinnamate has also been prepared by the careful distillation of phenyl fumarate.3... 

Several catalysts have been recommended for the N-acetylation of carbazole with acetic anhydride boron trifluoride, phosphorus pentoxide, concentrated sulfuric acid, zinc chloride, and phosphoric acid all gave 9-acetylcarbazole in moderate to good yield. 9-Acetylcarbazole can also be prepared using the Vilsmeier complex of N,N-dimethylacetamide and phosgene. ... 

Thenaldehyde (thiophene-2-carbaldehyde) is readily available via the Vilsmeier-Haack reaction of DMF with thiophene catalyzed by phosphorus oxychloride. The Sommelet reaction with 2-chloromethylthiophene also gives reasonable yields (63AHC(l)l). Likewise, thiophene is readily acylated with acyl anhydrides or acid chlorides (equation 14), using mild Friedel-Crafts catalysts, such as tin(IV) chloride, zinc chloride, boron trifluoride, titanium tetrachloride, mercury(II) chloride, iodine and even silica-alumina gels or low-calcium-content montmorillonite clays (52HC(3)l). 

However, this method is applied only when esterification cannot be effected by the usual acid—alcohol reaction because of the higher cost of the anhydrides. The production of cellulose acetate (see Fibers, CELLULOSE esters), phenyl acetate (used in acetaminophen production), and aspirin (acetylsalicylic acid) (see Salicylic acid) are examples of the large-scale use of acetic anhydride. The speed of acylation is gready increased by the use of catalysts (68) such as sulfuric acid, perchloric acid, trifluoroacetic acid, phosphorus pentoxide, zinc chloride, ferric chloride, sodium acetate, and tertiary amines, eg, 4- dimethylaminopyridine. 

Several dibasic acid halides are best prepared by this method from the readily available anhydrides. Thionyl chloride in the presence of a small amount of zinc chloride converts succinic and phthalic anhydrides to succinyl chloride (74%) and phthalyl chloride (86%), respectively. Phosphorus halides are used in similar preparations of phthalyl bromide (83%) and diphenic acid chloride (71%). ... 

In addition to the methods of preparation given in connection with the procedure for the acetylation of thiophene with acetyl chloride in the presence of stannic chloride, 2-acetothienone has been prepared from thiophene and either acetyl chloride or acetic anhydride in the presence of iodine, hydriodic acid, silica-metal oxides, zinc chloride, or inorganic oxyacids. It has also been prepared from thiophene and acetic acid in the presence of hydrogen fluoride or phosphorus pentoxide. The acylation in the presence of phosphorus pentoxide is particularly useful with higher aliphatic acids. ... 

ARSENOLITE or ARSENOUS ACID or ARSENOUS ACID ANHYDRIDE or ARSENOUS ANHYDRIDE (1327-53-3) AS2O3 Noncombustible solid. Reacts, possibly violently, with acids, aluminum, aluminum chloride, chlorine trifluoride, chromic oxide, fluorine, fluorides, halogens, hydrogen fluoride, mercury, oxygen fluoride, phosphorus pentoxide, rubidium acetylide, sodium chlorate, sodium hydroxide, sulfiiric acid, tannic acid, zinc iron in solution. Contact with acids or acid mists releases toxic and flammable arsine gas. The aqueous... 

PHOSPHORUS CHLORIDE (10025-87-3) Fumes in moist air. Contact with water, steam, or alcohols produces hydrochloric acid, phosphoric acid, and phosphine gas, which is pyrophoric, with possible ignition or explosion (may be a delayed reaction). Contact with air produces corrosive fumes. Violent reaction with carbon disulfide, 2,6-dimethylpyridine-iV-oxide, dimethyl sulfoxide, ferrocene l,l -dicarboxylic acid, pyridine, zinc powder. Reacts, possibly violently, with acids, alkali metals, alkalis, combustible materials, dimethyl for-mamide, organic matter, zinc powder. Incompatible with acetic anhydride, yV,V-dimethyl formamide, 2,5-dimethylpyrrole, sodium. Rapid corrosion of steel and most metals, except lead, occurs in the presence of moisture. 

Reactions of an alcohol with acetic anhydride are greatly accelerated by acid catalysts, such as sulfuric acid, zinc chloride, phosphorus pentoxide, ferric chloride, etc. However, such catalysts cannot be used with sensitive alcohols, such as linalool, which are isomerized or otherwise affected by them. The effective acid strength of a catalyst in an anhydrous medium is the predominant factor in determining its activity. The acidities of mineral acids in glacial acetic acid correspond remarkably well with their activities as acetylation catalysts. Sulfuric and perchloric acids in acetic acid solution have been termed superacid solutions because of thdr exceptional strength as compared with the strength of other acids. Most anhydrides react more rapidly with an alcohol in the presence of a base. The base can be sodium hydroxide, the sodium salt of the acid, or a tertiary amine, which can also be the solvent for the reaction. ... 

Route A involves the condensation of appropriately substituted phloro-glucinol derivatives with substituted orsellinic acid derivatives in the presence of anhydrous zinc chloride and phosphorus oxychloride. The analogous condensation in the presence of trifluoroacetic anhydride yielded the xanthone (150) (C-acylated product) as a minor byproduct together with the major aryl ester (151) (0-acylated product). However trifluoroacetic anhydride has become the reagent of choice (route B) since the use of 0-methyl and 0-benzyl protecting groups has enabled good yields of the xanthones to be obtained. 

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