Tetraphenylphthalic anhydride

Tetraphenylcyclopentadienone has been prepared by the action of phenylmagnesium bromide on benzaldiphenylmaleide,1 and by reduction, dehydration, and oxidation of the methylene-desoxybenzoin obtained by condensing formaldehyde with desoxy-benzoin.2 The present procedure is essentially that of Dilthey.3 

An intimate mixture of 35 g. (0.094 mole) of tetrapjjjenylcy-clopentadienone (p. 92) and 9.3 g. (0.095 mole) of maleic anhydride is placed in a 200-cc. round-bottomed flask (Note 1), and to ix is added 25 cc. of bromobenzene. After the mixture has been refluxed gently for three and one-half hours (Note 2), it is cooled 

Ground-glass equipment is preferred corks are attacked by the bromine used later. 

The operation should be carried out in a hood because of the carbon monoxide evolved. 

The tetraphenyldihydrophthalic anhydride may be isolated at this point in practically quantitative yields by cooling the mixture, filtering with suction, and washing the solid with three 10-cc. portions of petroleum ether (b.p. 60-68°). The yield is 41-42 g. the product melts at 235-240°. 

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Tetraphenylphthalic anhydride has been prepared by condensation of tetraphenylcyclopentadienone and maleic anhydride in nitrobenzene,1 followed by dehydrogenation of the tetraphenyl-dihydrophthalic anhydride with sulfur.2 3... 

Tetrachlorophthalic anhydride gave a relatively low yield of products derived from tetrachlorobenzyne. The pyrolysis tube was badly carbonized evidently extensive decomposition of the anhydride, the aryne, or the chlorinated products had occurred. Tetrabromophthalic anhydride gave a still lower yield of products. These are not listed in the table because none of them retained all four bromine atoms and could be definitely ascribed to reactions of tetrabromobenzyne, although tri-bromo- and dibromonaphthalene were present in appreciable amounts. Tetraphenylphthalic anhydride also gave low yields of products of the reaction of tetraphenylbenzyne with pyridine. This was not because of the stability of the anhydride and its reluctance to form the aryne, but rather because the aryne preferred to stabilize itself intramolecularly. The behavior of tetraphenylphthalic anhydride is discussed in another Section. 

Tetraphenylphthalic anhydride gave a poor yield of products with thiophene. Similar results had been found in its reaction with pyridine (Fields and Meyerson, 1966e). This anhydride is discussed in Section G. 

As tetraphenylphthalic anhydride behaved quite differently from the other aromatic anhydrides, its mass spectrum and reactions at high temperatures (Fields and Meyerson, 1967f) are described separately. A partial mass spectrum is shown in Table 12. 

The reaction products of tetraphenylphthalic anhydride with a variety of reagents are shown in Table 13. 

Pyrolytic studies on several other aromatic anhydrides proceed with ring contraction, presumably via aryne-cyclopentylidenecarbene interconversion. Tetraphenylphthalic anhydride 142 gave the green hydrocarbon 143, presumably via insertion of the intermediate carbene into the C—H bond of an adjacent phenyl group. 1,2-Naphthynes appear... 

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