Ketones tetraketones

On treatment with acetic anhydride in pyridine, the yellow tetraketone (68), the yellow triketone (66), and the diketone (67) afforded monoacetyl, diacetyl, and triacetyl derivatives, respectively. All these derivatives contained a tertiary acetoxyl group. However, comparisons of 1H-NMR spectra of the parent ketones with those of the acetyl derivatives indicated that a rearrangement of the molecule or a major conformational change must have occurred. On the basis of extensive H-NMR spectral analysis, structure 69 was proposed for the diacetyl derivative which was derived from the triketone 66. Structure 69 was justified on the basis of conformational arguments. 

Alder, K., Schmidt, C.-H. Substituting additions. III. Condensation of furan and Its homologs with a,p-unsaturated ketones and aldehydes. Synthesis of dl-, tri-and tetraketones of the aliphatic series. Ber. 1943, 76B, 183-205. 

Although tetraketones would be the simplest starting materials for the synthesis of resorcinols, for instance, 2,4,6,8-nonatetraone (82) for resorcinol 83 (equation 91), protected forms of tetraketones are normally used to avoid different possible cyclizations. Protected forms of 82 include the 2-acetal 84 , the 2,8-bisacetal 85 , the 2,8-bisenamine 86 , the acetylenic ketone 87, the 2,8-bis(hemithioacetal) 88 and the pyrones 89-91 (Chart 1) . 

We are told that oxidation of barbituric acid yields alloxan, which is the hydrated form of the tetraketone, CitHuNaOi,. By comparing the molecular formulas of barbituric acid and the tetraketone, we see that two hydrogens have been lost, and one oxygen added. Oxidation must therefore have occurred at the methylene carbon, forming the ketone, as shown below ... 

A computational study has been undertaken of the reaction between dimethyl perflu-orododecanedicarboxylate and alkyl ketones, to give polyfluorinated tetraketones. 2 -Benzoyl-biphenyl-2-carbaldehyde (161) can be converted into a phenanthrol derivative (162), using tosyl hydrazide (TSNHNH2) in toluene at 70 The reaction proceeds via selective formation of the A-tosylhydrazone at the aldehyde, followed by cyclization (using a strong base). The reaction is formally similar to a diazo-carbon... 

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