Cyclohexane 1,2,3-trione

Another synthesis of pyrogallol is hydrolysis of cyclohexane-1,2,3-trione-l,3-dioxime derived from cyclohexanone and sodium nitrite (16). The dehydrogenation of cyclohexane-1,2,3-triol over platinum-group metal catalysts has been reported (17) (see PLATINUM-GROUP METALS). Other catalysts, such as nickel, rhenium, and silver, have also been claimed for this reaction (18). 

Hydrolysis of cyclohexane-1,2,3-trione-l,3-dioxime (23, X = O) and its 2-imine (X = NH) has been studied in perchloric acid solution.91 The mechanism is proposed to involve a protonation pre-equilibrium, followed by slow water addition to protonated and non-protonated forms. Oxime protonation pXas have been calculated. 

Scheme 5. Formation of cyclohexane-1,2,3-trione l,3-bis(phenylhydrazone) by a free-radical mechanism.235-241...

The unexpected 8-hydroxymethylhexahydropyrido[2,3-, pyrimidine-6-spiro-l -cyclohexane-2, 4,6 -triones 520 were obtained from microwave-assisted cyclocondensation of equimolar amounts of 6-aminopyrimidin-4-ones 460 and dime-done with a large excess of formaldehyde (37% in water) in the presence of EtsN as a catalyst <2006TL27>. The reaction proceeded via an initial formation of the 2 1 dimedone/formaldehyde adduct 521 that gave intermediate 522 and 523 which could undergo cyclocondensation with excess formaldehyde to give 520 (Equation 42) <2006TL27>. 

Phloroglucinol, which is regarded as the tri-enol form of cyclohexane-1,3,5-trione, gives the hexahydrate of the corresponding perfluoro-trione upon fluorination in formic acid (Fig. 31) [93] (see 3.1.1.2 for a discussion of the fluorination of carbonyl compounds). 

Addition of p-nitrobenzenesulphonyl azide to 7-cycloprophylidene-dispiro[2.0.2.1]heptane leading to a cyclobutanone is a key step in a very nice approach to polyspiranes (equation 198)" . A unique ketene is an intermediate in the preparation of the dione and trione displayed in equation 199 which might serve as precursors for interesting sterically crowded cyclobutane and cyclohexane derivatives. 

The polyhydrazones of cyclopentane-l,3-diones and -1,2,3-triones, like their cyclohexane counterparts, are accessible from 1,3-diones. For example, cyclopentane- 1,3-dione yields cyclopentane-1,2,3-trione 3-phenylhydrazone... 

Scheme 11. Chelated structures of cyclohexane- and cyclopentane-1.2.3-trione tris (phenylhydrazones).270 271...

Filicinic Acid (2 4 6-Triketo-l l-dimethyl-cyclohexane, 1 l-dimethylcyeloItexane-2 4 6-trione, gem-dimethylphloroglucinol)... 

Cl5H12CI2S, cis-2,2-Dipheny1-3,4-dichlorothietane, 4IB, 409 Cl5H12O3S6, 2,4,6-Tris(1,3-dithiolan-2-ylidene)-cyclohexane-1,3,5-trione, 46B, 361... 

Preparation by catalytic hydrogenolysis of 2-acetyl-4,4-bis-(3-methylbut-2-enyl)cyclohexane-l,3,5-trione at r.t. and pressure in the presence of 10% Pd/C in ethanol (93%) [3477]. 

The tautomeric cyclohexane-1,3,5-trione system of humulone contains a crossed acyloin chromophore. Consequently, two alternative acyloin rearrangements with concurrent ring contraction could be possible. In addition to the "normal" series of isohumulones and derivatives (see Chapter 5), an "inverse" isomerization could, therefore, occur leading to the series of the anti-isohumulones and derivatives. 

Wollmer suggested a cyclohexane-1,3,5-trione structure with four side chains, of which the two geminal side chains would be C5Hg-fragments. For the two other... 

Upon alkaline fusion of lupulone the following acids and ketones have been obtained, in addition to carbon dioxide acetic acid and 5-(3-methyl-2-butenyl)-2,10-dimethylundeca-2,9-dien-6-one 5-methyl-4-hexenoic acid and 3-(3-methyl-2-butenyl)-6-methyl-5-hepten-2-one 2-(3-methyl-2-butenyl)-5-methyl-4-hexenoic acid and 6-methyl-5-hepten-2-one (see also 14.4.). The position of the double bonds in these compounds has been confirmed by ozonolysis, whereby only acetone was isolated, The same result has been obtained by direct ozonization of lupulone (9,10). Consequently, lupulone is the enolized 2-(3-methylbutanoyl)-4,6,6-tris-(3-methyl-2-butenyl)-cyclohexane-1,3,5-trione (23, Fig. 77). The structure has been proved by synthesis (see 11.4.). 

Colupulone was discovered when the hydrogenolysis of hop beta acids afforded a tribenzoate with a melting point of 134°C (11,12). The hydrogenolysis product yielding this particular tribenzoate is 4,6-bis(3-methylbutyl)phlorisobutyrophenone (171, Fig. 78). Oxidation and subsequent alkaline hydrolysis gave dihydrocohumulinic acid (172, Fig. 78). It was deduced that the substrate is 4,6,6-tris(3-methyl-2-butenyl)-2-(2-methylpropanoyl)-cyclohexane-1,3,5-trione (170, Fig. 78) or colupulone, by analogy with cohumulone (8, Fig. 7) (see 2.1.2.). The structure has been confirmed by synthesis (see 11.4.). 

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