Ketone Systems

An example of the calculation of the wavelength of the absorption maximum using Table 5.7 is shown in Example 5.6. In this example the calculations are similar to 

An isomer of the molecule used in Example 5.6 is shown in Example 5.7. The calculated absorption maximum is 286 nm. This spectrum is different in several ways from Example 5.6. For example, the carbon at the S position has only one alkyl substitution. 

Value assigned to parent a,)3-unsaturated six-ring or acychc ketone 215 Value assigned to parent a,jS-unsaturated five-ring ketone 202 Value assigned to parent a,j8-unsaturated aldehyde 207 

The double bond between the y and 8 positions is exocyclic to a ring in this case and therefore increases the wavelength of the absorption maximum. The conjugated system is not within a ring, and therefore contributions from ring currents are not observed. These two isomers could be distinguished from each other by their UV spectra. 

The calculation of the absorption wavelength maximum for Example 5.8 is shown to be 286 nm. The calculation follows the steps used in previous examples. It should again be emphasized that the parts of the molecule that do not touch the conjugated or parent system do not shift the absorption maximum. This is true even for complex molecules, as some of these examples demonstrate. This makes prediction of the absorption maximum easier but the absorption maximum gives no information as to the structure of the entire molecule. 

---

Alcohol-ketone systems Minimum boiling azeotropes None ... 

The photochemical addition of simple olefins to a,j -unsaturated ketones is a reaction of great current interest. The steroidal A -20-ketone system is especially prone to cycloaddition under mild conditions. Sunder-Plassmann et irradiated 3j5-acetoxypregna-5,16-dien-20-one (67) in the presence... 

An acetoxyl group at C-21, if present, is retained and an a,) -unsaturated ketone system in ring A does not interfere. 

In an epoxy-ketone system such as 4yS,5j8-epoxy-6y -fluoroandrostane-3,17-dione (430), fluorination (by the Olah reagent ) occurred as in an Sn2 type of mechanism, giving 2y ,6 -difluoroandrost-4-ene-3,17-dione (431). This procedure may be applicable to sugars. 

Several studies, however, conclusively showed that the intensity of the sweet taste depends strongly upon the number of hydroxyl groups in the A-ring. - - For example, compound 85 and its sodium salt, which have only one hydroxyl group in the A-ring, are less sweet than the 2,6-dihydroxy compound. Furthermore, there is also a requirement for an orrto-hydroxy ketone system in ring A, as compound 86 is tasteless, and because it had already been shown that the alkoxy-hydroxy substituents on ring B are also... 

Transfer hydrogenation in the alcohol-ketone system on metal catalysts was investigated by Patterson et al. In particular, by studying the reaction between 2-propanol and butanone on Cu they concluded that it must be a direct surface reaction (11), the mechanism being essentially a proton transfer in the adsorbed phase (Scheme 2). 

Surh YJ, Lee SS. (1992). Enzymatic reduction of shogaol a novel biotransformation pathway for the alpha, beta-unsaturated ketone system. Biochem Int. 27(1) 179-87. 

Narasimhan, K.S., Reddy, C.C., and Chari, K.S. Solubility and equilibrium data of phenol-water-isoamyl acetate and phenol-water-methyl isobutyl ketone systems at 30 °C, J. Chem. Eng. Data, 7(4) 457-460, 1962. 

An enolate anion generated from a carboxylic acid derivative may be used in the same sorts of nucleophilic reactions that we have seen with aldehyde and ketone systems. It should be noted, however, that the base used to generate the enolate anion must be chosen carefully. If sodium hydroxide were used, then hydrolysis of the carboxylic derivative to the acid (see Section 7.9.2) would compete with enolate anion formation. However, the problem is avoided by using the same base, e.g. ethoxide, as is present in the ester... 

AlR3-ketone system AlR3-acidamide system... 

Pressure has a marked effect on the azeotropic composition and vapor-liquid equilibrium diagrams of alcohol-ketone systems (J). This is due to the fact that the slopes of the vapor pressure curves of alcohols are appreciably greater than for ketones it results in an unusually larger change in the relative boiling points of the components of an alcohol-ketone system with change in pressure. 

Figure 1. Vapor-Liquid Equilibrium Diagrams of Alcohol-Ketone Systems...

As a function of corresponding average composition of vapor and liquid for alcohol-ketone systems... 

An impressive new route to enantiopure syn- and anti- 1,2-diols involves sequential diastereoselective DIBAL reduction of oxalyl-di(/V-iucthyl-/V-methoxyainide) following conversion to a corresponding intermediate / -keto sulfoxide a route that involved control of both reductions by the chiral sulfoxide auxiliary.253 Comparison of / -hydroxy ketone systems with die y-sulfoxide-/ -keto systems used here showed this to be die first example of such asymmetric induction by a y-sulfoxide substituent. 

Die intramolekulare photochemische C4-Ringbildung zwischen einem a.B-ungesiittigten Keton-System und einer Doppelbindung ist seit langem bekannt (vgl. die Photoisomerisierung des Carvons, Kap. 3.1.). Zahl-... 

In aprotic solvents, an increase in solvent polarity resulted in an increase in the amount of ds-0-decalone formed. Similar results were also obtained in the hydrogenation of cholestenone and testosterone (see Table I). If, as suggested by McQuillin et al. (3), a more polar aprotic solvent will facilitate complexation of the carbonyl oxygen of an a,j3-unsaturated ketonic system in the same way that it increases its polarization (25), it can be assumed that what is occurring in these polar solvents is a 1,4-addition of hydrogen to the conjugated system. 

The hydrogenation of hydrindenones with the unsaturated ketonic system in either the five- or six-membered ring (XXXIII and XXXIV) gives almost exclusive cis-product formation, regardless of the nature of the solvent used or the type of angular substituent present (22, 44-46). The presence of a substituent at the 4-position in 9-methyl-hydrind-4-ene-3-ones (XXXV) leads to preferential trans-isomer formation (45-48). The fact that the 4-substituent in the saturated... 

The anti-inflammatory activity of curcumin and its derivatives is associated with the hydroxyl and phenol groups in the molecule, which are also essential for the inhibition of prostaglandins, PG synthetase and leucotriene synthesis (LT) (Kiuchi et al., 1982, 1992 Iwakami, et al, 1986). Claeson et al. (1993, 1996) suggested that the antiinflammatory action and the antiparasitic activity were associated with the (3-dicarbo-nylic system with conjugated double bonds (dienes) (Araujo et al., 1998, 1999). The better skin penetration and lipophylicity is attributed to the presence of a diene ketone system. Calebin-A, a novel curcuminoid isolated from turmeric, protects neuronal cells from (3-amyloid insult. The hydroxy group at para-position of this compound is most critical for the expression of biological activity (Kim et al., 2001). 

In spite of all the attempts discussed above, and others which have subsequently been reported (81, 82, 83), no satisfactory means of degrading gelsemine has yet been discovered, with the possible exception of Conroy s conversion of gelsemine into the ketone (XIV). A by-product in the formation of XIV was a neutral substance exhibiting carbonyl absorption at 1720 cm-1. This might well be the result of reverse Mannioh decomposition of the 3-amino ketone system present in XIV unfortunately, the structure of this product has not been established and the degradation has not been pursued beyond this point. 

Another interesting reaction type detected from the photoreaction of tertiary amine-ketone system which have found use in alkaloids chemistry [172] involves sequential electron transfer and proton transfer followed by back electron transfer to yield iminium cations (Eq. 35) leading to dealkylation products upon aqueous workup. The regiocontrol in these dealkylations is dictated by preferential deprotonation at the less branched amine cation radical a-carbon. 

Photo induced interconversion of the configuration at an asymmetric C atom, has not been reported. For tyrosine it has been excluded even under high-intensity laser irradiation [66]. This chiral unit seems to be very stable. A bicyclic ketone system with (formal) double epimerization is described by Zandomeneghi et al. [67] (Eq. 33). This reaction proceeds, however, by a complex rearrangement mechanism and will be discussed in Sec. II.B. 

For example, L and D might be the left- andright-handed enantiomers of a chiral alcohol, and B is the ketone derived from this alcohol (see Fig. 14). In this case, studies [83] of the electronic structure of the alcohol-ketone system show that there are weakly bound chiral alcohol-ketone minima in the ground electronic state, as desired. The particular advantage of using the ketone-alcohol complex is that the ketone, which is recycled after the conversion of one enantiomer to another, serves as a catalyst for the process. 

Fortunately additional x-data can be deduced from the data reported in Table XIX of Ref. 43, based on the assumption that % at a given T varies linearly with v, which was inferred [180] from the plots of % at 25 °C vs v for the polyisobutylene-benzene and polystyrene-methyl ethyl ketone systems recorded respectively in Figs. 1 and 2 of Ref. 43. These correlations show that for these two P-L systems X tends to increase linearly with v from Xo = about 0.48 at v = 0 to Xi = about 0.85 at v = 1.0. 

---