Tricarbonyl Compounds

Exercise 17-48 Write a reasonable mechanism, supported by analogy, for the acid-catalyzed dehydration of 2,5-hexanedione to 2,5-dimethyloxacyclopenta-2,4-diene, 17. 

The properties of tricarbonyl compounds are for the most part as expected, except when the three groups are contiguous to one another, as in diphenyl-propanetrione. With such compounds, the central carbonyl group is highly reactive it is lost, as carbon monoxide, in the presence of acidic catalysts such as aluminum chloride, and adds water readily to give a monohydrate  

We shall consider the hydrate of the cyclic triketone, 18, known as ninhydrin, later in connection with amino acids  

Exercise 17-49 Devise a synthesis of diphenylpropanetrione from 1,3-diphenyl-1,3-propanedione, (C6H5CO)2CH2. How could you determine whether the center or one of the flanking carbonyl groups is lost, as carbon monoxide, with aluminum chloride  

Exercise 17-50 What properties would you expect for 1,3,5-cyclohexanetrione  

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The Chemistry of Ninhydrins and Other Cyclic 1,2,3-Tricarbonyl Compounds A. Schoenberg and E. Singer, Tetrahedron, 1978, 34, 1285-1300. 

On the other hand, the oxidation of some sulfides with Dess-Martin periodinane provides an unique way to prepare some 1,2,3-tricarbonyl compounds, which are very difficult to obtain.37... 

Both the alcohol and the sulfide are oxidized by Dess-Martin periodinane, resulting in a 1,2,3-tricarbonyl compound that is very difficult to obtain by other means. 

Tricarbonyl compounds can also be obtained by treatment of (3-hydroxycarbonyl compounds—without a sulfur atom at the a—position— with Dess-Martin periodinane.38... 

TABLE 11.4 1,2,3-Tricarbonyl compounds by Dess-Martin oxidation of various precursors ... 

Pyridazinones were obtained from an attempted Fischer indolization of a cyclopentanone phenylhydrazone [85CI(L)697], from hydrazones of unsaturated 1,4-keto esters (87H2101) or from 3-arylhydrazones of 4-(4-methoxyphenyOglutaconic anhydride in the presence of seconday amines [83IJC(B)512]. Pyridazines 6 can be synthesized from 2-phenylhydrazones of 1,2,3-tricarbonyl compounds and phosphacumulenylides (80TL2939 85CB1709). 

Some other electron-deficient ketones have been used as dienophiles in Diels-Alder reactions. Various types of 1,2,3-tricarbonyl compounds seem to be quite reactive in this type of process, and some selected examples are listed in Table 4-III.26-28... 

Quinoxalinyl ketones have been prepared by application of the classical quinoxaline synthesis, an o-phenylenediamine being condensed with an appropriate 1,2,3-tricarbonyl compound. Reactions of this type do not provide an unambiguous synthesis of quinoxalinyl ketones, since an alternative mode of condensation is possible leading to a benzo-1,5-diazepinone. The latter possibility is eliminated in the example cited in Scheme 1 because NMR examination of the condensation product... 

Tricarbonyl compounds. 1,3-Dicarbonyl compounds can be converted into 1,2,3-tricarbonyl compounds by monobromination (bromine and pyridine or triethylamine) followed by Kornblum oxidation (1, 303) in DMSO at 70-80° ... 

Tri- -butylstannane, 649 l-Tri-/t-butylstannyl-l-propene-3-letra-hydropyranyl ether, 602-603 Tri-n-butyltin chloride, 604 Tri-n-butyltin hydride, 604 1,2,3-Tricarbonyl compounds, 227 Trichloroacetonitrile, 604-605... 

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