Carbonic acid anhydrides selective

Selected examples of carboxylic acid anhydrides and carbonic hemiester anhydrides... 

Infrared spectra of propene and isobutene on different catalysts were measured by Gorokhovatskii [143]. Copper oxide, which converts olefins to butadiene and aldehydes, shows adsorption complexes different from structures on a V2Os—P2Os catalyst which produces maleic acid anhydride. Differences also exist between selective oxidation catalysts and total oxidation catalysts. The latter show carbonate and formate bands, in contrast to selective oxides for which 7r-allylic species are indicated. A difficulty in this type of work is that only a few data are available under catalytic conditions most of them refer to a pre-catalysis situation. Therefore it is not certain that complexes observed are relevant for the catalytic action. 

The course of the decomposition of the mixed anhydrides [Scheme 44] which leads to the formation of expected esters (path A) or to a mixture of symmetrical carbonates and anhydrides (path B) strongly depends on the structures of the chloroformate and the carboxylic acid but also on the choice of the catalyst.. Because selective production of esters if of great interest, we have studied the thermal instability of the mixed anhydrides and developed a new efficient and selective esterification reaction with chloroformates using a silica supported guanidinium catalyst (Ref. 39). This method will be discussed in vol. 2 section 4-4. 

Depending on the technology employed, once-Ahrough conversion varies from 30 to 80 per cent and molar yields from 50 to 80 per cent for acetic anhydride, and 15 to 45 per cent for the acid. The main by-products are carbon dioxide, methyl acetate, acetone, ethylidene diacetate and various heavy components, whose recycling serves to improve the anhydride selectivity. 

Tohda et al. reported on the use of 2-primary alkyl 4,4-dimethyl-2-oxazolines in a crossed Claisen condensation (equation IS). The 2-primary alkyl oxazoline was treated with an acid anhydride in the presence of aluminum chloride and triethylamine in acetonitrile to give moderate yields (typically 50-65%) of the oxazoline derivative of a P-keto acid. The product can be monoalkylated selectively on the carbon adjacent to the heterocyclic ring, while the 2-oxazoline group can be converted into a variety of functional groups. 

Anderson and Webster (10) showed the pyridyl-silicon bond of 2-(trimethylsilyl)pyridine to be susceptible to cleavage by alcohol and water to form unsubstituted pyridine. Thames and coworkers (11) showed that neutral reagents, including aldehydes, acid halides, chloroformates, and anhydrides, have the ability to cleave several silicon-carbon bonds on select heterocycles (Schemes VI-VIII). However, the silicon-carbon bond of nonheterocycles is not susceptible to neutral reagent cleavage, and too, the full extent of heterocyclic cleavage reactions is not known. 

Process Technology Evolution. Maleic anhydride was first commercially produced in the early 1930s by the vapor-phase oxidation of benzene [71-43-2]. The use of benzene as a feedstock for the production of maleic anhydride was dominant in the world market well into the 1980s. Several processes have been used for the production of maleic anhydride from benzene with the most common one from Scientific Design. Small amounts of maleic acid are produced as a by-product in production of phthaHc anhydride [85-44-9]. This can be converted to either maleic anhydride or fumaric acid. Benzene, although easily oxidized to maleic anhydride with high selectivity, is an inherently inefficient feedstock since two excess carbon atoms are present in the raw material. Various compounds have been evaluated as raw material substitutes for benzene in production of maleic anhydride. Fixed- and fluid-bed processes for production of maleic anhydride from the butenes present in mixed streams have been practiced commercially. None of these... 

Nickel Arsenate. Nickel arsenate [7784-48-7] Ni2(As0 2 8H20, is a yellowish green powder, density 4.98 g/cm. It is highly iasoluble ia water but is soluble ia acids, and decomposes on heating to form As20 and nickel oxide. Nickel arsenate is formed by the reaction of a water solution of arsenic anhydride and nickel carbonate. Nickel arsenate is a selective hydrogenation catalyst for iaedible fats and oils (59). 

Fig. 2. Synthesis of uma2enil (18). The isonitrosoacetanihde is synthesized from 4-f1iioroani1ine. Cyclization using sulfuric acid is followed by oxidization using peracetic acid to the isatoic anhydride. Reaction of sarcosine in DMF and acetic acid leads to the benzodiazepine-2,5-dione. Deprotonation, phosphorylation, and subsequent reaction with diethyl malonate leads to the diester. After selective hydrolysis and decarboxylation the resulting monoester is nitrosated and catalyticaHy hydrogenated to the aminoester. Introduction of the final carbon atom is accompHshed by reaction of triethyl orthoformate to...

Aiyl esters, prepared from the phenol and an acid chloride or anhydride in the presence of base, are readily cleaved by saponification. In general they are more readily cleaved than the related esters of alcohols, thus allowing selective removal of phenolic esters. 9-Fluorenecarboxylates and 9-xanthenecarboxylates are also cleaved by photolysis. To permit selective removal, a number of carbonate esters have been investigated aryl benzyl carbonates can be cleaved by hydrogenolysis aryl 2,2,2-trichloroethyl carbonates, by Zn/THF-H20. 

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