Decarbonylation anhydrides

Substituted aroyl- and heteroaroyltrimethylsilanes (acylsilanes) are prepared by the coupling of an aroyl chloride with (Me3Si)2 without decarbonylation, and this chemistry is treated in Section 1.2[629], Under certain conditions, aroyl chlorides react with disilanes after decarbonylation. Thus the reaction of aroyl chlorides with disilane via decarbonylation is a good preparative method for aromatic silicon compounds. As an interesting application, trimel-litic anhydride chloride (764) reacts with dichlorotetramethyidisilane to afford 4-chlorodimethylsilylphthalic anhydride (765), which is converted into 766 and used for polymerization[630]. When the reaction is carried out in a non-polar solvent, biphthalic anhydride (767) is formed[631]. Benzylchlorodimethylsilane (768) is obtained by the coupling of benzyl chloride with dichlorotetramethyl-disilane[632,633]. 

The decarbonylation-dehydration of the fatty acid 887 catalyzed by PdCl2(Ph3P)2 fO.Ol mol%) was carried out by heating its mixture with acetic-anhydride at 250 C to afford the terminal alkene 888 with high selectivity and high catalyst turnover number (12 370). The reaction may proceed by the oxidative addition of Pd to the mixed anhydride[755]. 

A sample of redistilled material in a screw capped bottle exploded 15 weeks after capping. This was attributed to development of internal pressure (probably of hydrogen chloride arising from hydrolysis, and perhaps also of chloromethane from scission). (The editor has also known methoxyacetic mixed anhydrides to decarbonylate, releasing carbon monoxide)... 

An interesting reaction of methyl formate is its isomerization to give acetic acid. Based on patent literature, a number of companies have recently reinvestigated this isomerization which has been known for over 30 years ( ). It is unlikely that it can compete with the Monsanto process however, since it doesn t need pure CO and may be operable at milder reaction conditions, some potential may be seen. Combining isomerization to acetic acid and decarbonylation to methanol and CO, could provide a direct synthesis for acetic anhydride starting directly from methyl formate (Equation 13). 

In some cases, the product depends on the nature of the acylating agent. Acylation of 182 with 2,2-difluoro-4-pentenoic acid anhydride leads to acylation at C, whereas acylation with 2,2-difluoro-4-pentenoic acid choride yields the 5-acyloxyoxazole 185 as the major compound. The 5-acyloxyoxazole can be rearranged to the 5(47/)-oxazolone 183 upon treatment with 4-(dimethylamino)pyridme. Treatement of 183 with anhydrous oxalic acid promotes decarbonylation to give fluorinated a-amino ketones 184 (Scheme 7.55). Selected examples of 4-acyl-5(4//)-oxazolones are shown in Table 7.20 (Fig. 7.22). 

Mesylates are used for Ni-catalysed reactions. Arenediazodium salts 2 are very reactive pseudohalides undergoing facile oxidative addition to Pd(0). They are more easily available than aryl iodides or triflates. Also, acyl (aroyl) halides 4 and aroyl anhydrides 5 behave as pseudohalides after decarbonylation under certain conditions. Sulfonyl chlorides 6 react with evolution of SO2. Allylic halides are reactive, but their reactions via 7t-allyl complexes are treated in Chapter 4. Based on the reactions of those pseudohalides, several benzene derivatives such as aniline, phenol, benzoic acid and benzenesulfonic acid can be used for the reaction, in addition to phenyl halides. In Scheme 3.1, reactions of benzene as a parent ring compound are summarized. Needless to say, the reactions can be extended to various aromatic compounds including heteroaromatic compounds whenever their halides and pseudohalides are available. 

Under certain conditions, aroyl chlorides are converted to arylsilanes by the reaction with disilanes. The oxidative addition of aroyl chloride and decarbonylation are followed by transmetallation and reductive elimination to give aryl silanes. Neat trimellitic anhydride acid chloride (377) reacts with dichlorotetramethyldisilane (376) at 145 °C to generate 378, which affords 4-chlorodimethylsilylphthalic anhydride (379) by reductive elimination. Finally it was converted to 380 and used for polyimide formation [185], Biphenyltetracarboxylic anhydride 381 is obtained at a higher... 

Di-(l-naphthylmethyl)sulphone forms an excimer but does not react to give an intramolecular cycloaddition product like the corresponding ether but rather fragments to give sulphur dioxide and (l-naphthyl)methyl radicals (Amiri and Mellor, 1978). I-Naphthylacetyl chloride has a very low quantum yield of fluorescence and this is possibly due to exciplex formation between the acyl group and the naphthalene nucleus (Tamaki, 1979). Irradiation leads to decarbonylation. It is known that acyl chlorides quench the fluorescence of aromatic hydrocarbons and that this process leads to acylation of the aromatic hydrocarbon (Tamaki, 1978a). The decarboxylation of anhydrides of phenylacetic acids [171] has been interpreted as shown in (53), involving... 

Because stoichiometric amounts of base-HX salts are produced in a Heck reaction, alternative sources of aryl groups have been investigated. Carboxylic acid anhydrides were found to react with a PdC2/NaBr catalyst system, where the by-products were CO and a carboxylic acid, p-Nitrophenylbenzoates were also found to be aryl donors in a decarbonylative Heck reaction. An arylation of cinnamates was discovered using Pd(OAc)2 to activate... 

The intrinsic low thermodynamic stability of most formyl derivatives of transition metals (with respect to the decarbonylation product) is confirmed by the observation that when these compounds are prepared by an indirect route, they normally undergo decarbonylation. For example, a formyl derivative of iron(O) was synthesized by reacting [Fe(CO)4] " with acetic-formic anhydride [reaction (c)] however the resulting product [reaction (d)], decarbonylated slowly (ti/2 12 days at 25°C) ... 

Decarbonylation. Sheehan and Frankenfeld treated a-imilino-a,a-diphenylacetic acid (1) with tosyl chloride in pyridine with the expectation of obtaining the N-tosyl derivative but instead characterized the products as benzophenone anil (3), carbon monoxide, and pyridinium tosylate. They postulate the intermediate formation of the mixed anhydride (2). 

Removal of the furan ring (148) was accomplished in two steps in 45% overall yield from carboxylic acid 125 (Scheme 24) [57]. Carboxylic acid 125 was coupled with selenophenol via the mixed anhydride using phenyl dichlorophosphate to give the phenyl seleno ester. Decarbonylation of the phenyl seleno ester was accomplished with tributyltin hydride and AIBN in toluene. 

Cooke, R. S., Lyon, G. D. J. Am. Chem. Soc. 93, 3840 (1971) here also decarbonylations of five-membered ring anhydrides, like e.g. phthalic acid anhydride (further products C02 and dehydrobenzene) should be mentioned Dunkin, I. R., MacDonald, J. G. Tetrahedron Lett. 23, 4839 (1982) and lit. cit. therein... 

Disilanes have been used in stoichiometric amounts as reductants in the palladium-catalyzed coupling of electron deficient aryl chlorides. By this procedure, trimellitic anhydride acid chloride (70) was converted to the high temperature polymer precursor biphenyl dianhydride (71) in 85% yield with concomitant decarbonylation (see Scheme 35 [128]). 

In contrast, the adduct (41) obtained from singlet oxygen and l,4-diphenyl-3/7-2-benzopyran-3-one (40) is a stable, crystalline solid (Scheme 2) <78JA2564>. Nonetheless, (41) decomposes in boiling benzene giving o-dibenzoylbenzene (43) and phenyl o-benzoylbenzoate (45) in 85% and 5% yield respectively. No luminescence is detected. The major reaction course is decarboxylation to the intermediate o-xylylene peroxide (42), which can be trapped as its Diels-Alder adduct with maleic anhydride. The ester (45) could have arisen directly from (41) by decarbonylation and concomitant... 

Maier has reviewed the synthesis of cyclobutadienes, including the photochemical syntheses by decarbonylation and decarboxylation of anhydrides.147 The diones (250a—c) yield the olefins (251) by double decarbonylation on irradiation in methylene chloride.148 Formation of the olefins suggests that the... 

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