Diphenylacetic anhydride

The reduction of a-amino mixed anhydrides with lithium tri-/ert-butoxyaluminum hydride in THF at —70 °C is a very efficient method for synthesis of amino aldehydes (Table 9). 551 Three approaches were taken for the reduction of a-amino mixed anhydrides. 55 The first approach reduced Boc-Ala-OC02Et with lithium tri-terf-butoxyaluminum hydride was unsuccessful due to intramolecular rearrangements that gave Boc-Ala-OEt in addition to the Boc-Ala-H. The second approach involved reduction of diphenylacetic anhydride derivatives, which were prepared from Boc amino acids and diphenyl ketene, gave a diphenylacetic acid byproduct that was very difficult to remove unless the aldehyde was converted into its semicarbazone and separated chromatographically yields were 51-69%. The last and... 

The high-boiling ketenes are separated from the diphenylacetic anhydride by extraction rather than by distillation in order to avoid a ketene interchange. In this manner, many types of ketoketenes have been formed, including dimethylketene (49%), diallylketene (80%), dibenzyl-ketene (74%), ethylchloroketene CjH5ClC = CO (50%), and methylphenyl-ketene (75%). ... 

The mixed anhydride (10 g.) is placed in a small Claisen flask connected to a receiver cooled in Dry Ice and acetone and is heated under a pressure of about 11 mm. and at a bath temperature of 90-100°. Decarboxylation proceeds fairly rapidly, and dipropylketene (b.p. 30°/ll mm.) distils into the cooled receiver. Diphenylacetic anhydride remains in the distillation flask. On the basis of the amount of dipropylacetanilide formed when aniline is added to the distillate, the yield of dipropylketene is 32%. ... 

Acyl radicals and acyl anions are proposed intermediates in the reduction of phenylacetyl chloride and hydrocinnamoyl chloride at mercury in MeCN [223]. Among the products obtained from the reduction of phenylacetyl chloride are 1,4-diphenyl-2-butene-2,3-diol diphenylacetate, phenylacetaldehyde, toluene, 1,3-diphenyl-acetone, and l,4-diphenyl-2,3-butanediol, as well as phenylacetic acid and phenylacetic acid anhydride. Analogous products arise from the reduction of hydrocinnamoyl chloride l,6-diphenyl-3-hexene-3,4-diol dihydrocinnamate, hydrocinnamaldehyde, ethyl benzene, l,6-diphenyl-3,4-hexanediol, hydrocinnamic acid, and hydrocinnamic acid anhydride. 

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). 

A novel formal decarboxylation of the amino acid a-anilino-a,a-diphenylacetic acid has been observed upon treatment with tosyl chloride in pyridine. It has been proposed that a mixed anhydride of p-toluenesulfonic acid has undergone an elimination viaiV-deprotonation and synchronous extrusion of carbon monoxide in this reaction. Interestingly, no A-tosylation occurs (eq 22). 

A more common method involves the decomposition of mixed anhydrides, nearly all of which have been obtained by treating the dialkyl-malonic Acid, dissolved in dry ether, with diphenylketene. The resulting mixed anhydrides, derived from the malonic acids and diphenylacetic acid, are nearly insoluble in ether and separate in almost quantitative yields. They are decomposed by heating under diminished pressure untU... 

In 2010, a similar strategy was successfully applied to the KR of various 2-hydroxy alkanoates [57]. Indeed, the combination of BTM (23), pivalic anhydride, and diphenylacetic acid effectively produced the corresponding 2-acyloxyalkanoates in selectivities ranging from s = 47 to 202 (Scheme 41.11). 

Formamidinesulfinic acid, F-00036 Levometiomeprazine, in M-00069 Diphenylacetic acid Anhydride, in D-00999 A -(2-Hydroxy-3-methoxybenzylidene)-2-hydroxyaniline, in D-00541... 

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