Ketones hydroxyketones

After the first hydrolytic step, secondary alcohols seem to continue biodegradation through ketone, hydroxyketone, and diketone. Diketones then produce a fatty acid and a linear aldehyde which is further oxidized to fatty acid. Finally, these two fatty acids continue biodegradation by enzymatic 3 oxidation [410],... 

Also via Ketoacids Section 320 (Carboxylic Acid - Ketone) Hydroxyketones Section 330 (Alcohol - Ketone)... 

In addition to the reduction of ketones (e.g., aromatic and aliphatic ketones, a-halo ketones, hydroxyketones, enones, and ketoesters), oximes can be reduced to the corresponding amine with this reagent. In general, ketone oxime ethers, such as 39, can give rise to amines 40 in excellent chemical yield with good to excellent optical purity.5d... 

Tert. alcohols from ketones -Hydroxyketones from 2 ketone molecules... 

Both aldoses and ketoses reduce Fehling s solution (for details, see under 4). This fact may appear surprising when it is remembered that Fehling s solution is one of the reagents for distinguishing between aldehydes and ketones (see 4). The explanation lies in the fact that a-hydroxyketones are much more readily oxidised than simple ketones, perhaps because the hydroxy ketone allows its isomerisation, in the presence of alkali, into an aldehyde. For example, fructose, a keto-hexose, might Isomerlse thus ... 

Terminal alkyne anions are popular reagents for the acyl anion synthons (RCHjCO"). If this nucleophile is added to aldehydes or ketones, the triple bond remains. This can be con verted to an alkynemercury(II) complex with mercuric salts and is hydrated with water or acids to form ketones (M.M.T. Khan, 1974). The more substituted carbon atom of the al-kynes is converted preferentially into a carbonyl group. Highly substituted a-hydroxyketones are available by this method (J.A. Katzenellenbogen, 1973). Acetylene itself can react with two molecules of an aldehyde or a ketone (V. jager, 1977). Hydration then leads to 1,4-dihydroxy-2-butanones. The 1,4-diols tend to condense to tetrahydrofuran derivatives in the presence of acids. 

The selective intermolecular addition of two different ketones or aldehydes can sometimes be achieved without protection of the enol, because different carbonyl compounds behave differently. For example, attempts to condense acetaldehyde with benzophenone fail. Only self-condensation of acetaldehyde is observed, because the carbonyl group of benzophenone is not sufficiently electrophilic. With acetone instead of benzophenone only fi-hydroxyketones are formed in good yield, if the aldehyde is slowly added to the basic ketone solution. Aldols are not produced. This result can be generalized in the following way aldehydes have more reactive carbonyl groups than ketones, but enolates from ketones have a more nucleophilic carbon atom than enolates from aldehydes (G. Wittig, 1968). 

The 1,6-difunctional hydroxyketone given below contains an octyl chain at the keto group and two chiral centers at C-2 and C-3 (G. Magnusson, 1977). In the first step of the antithesis of this molecule it is best to disconnect the octyl chain and to transform the chiral residue into a cyclic synthon simultaneously. Since we know that ketones can be produced from add derivatives by alkylation (see p. 45ff,), an obvious precursor would be a seven-membered lactone ring, which is opened in synthesis by octyl anion at low temperature. The lactone in turn can be transformed into cis-2,3-dimethyicyclohexanone, which is available by FGI from (2,3-cis)-2,3-dimethylcyclohexanol. The latter can be separated from the commercial ds-trans mixture, e.g. by distillation or chromatography. 

Sodium or tetramethylammonium triacetoxyborohydride has become the reagent of choice for diastereoselective reduction of P-hydroxyketones to antidiols. Trialkylborohydrides, eg, alkaH metal tri-j -butylborohydrides, show outstanding stereoselectivity in ketone reductions (39). 

The unique chemical behavior of KO2 is a result of its dual character as a radical anion and a strong oxidizing agent (68). The reactivity and solubiHty of KO2 is gready enhanced by a crown ether (69). Its usefiilness in furnishing oxygen anions is demonstrated by its appHcations in SN2-type reactions to displace methanesulfonate and bromine groups (70,71), the oxidation of benzyHc methylene compounds to ketones (72), and the syntheses of a-hydroxyketones from ketones (73). 

Treatment of a-hydroxy-ketones or -aldehydes with ammonium acetate (65BSF3476, 68BSF4970) results in the formation of dihydropyrazines, presumably by direct amination of the hydroxyketone followed by self-condensation (79AJC1281). Low yields of pyrazines have been noted in the electrolysis of ketones in admixture with KI and ammonia, and again it appears probable that the a-aminoketone derived by way of the a-iodoketone is the intermediate (69CI(L)237>. 

By similar procedures diazirines were prepared not only from simple aliphatic ketones but also from hydroxyketones and )3-aminoketones (B-67MI50800), and so were a large number of diazirines from steroidal ketones (65JA2665). Permanganate, bromine, chlorine and hypochlorite were used as oxidants. A one-step preparation of diazirines from ketones like 3-nonanone, ammonia and chlorine has been claimed in a patent (66USP3290289). 3,3-Diazirinedicarboxylic acid derivatives like (286) were obtained directly from oxime tosylates by the action of two moles of O-ethoxyamine (81AG(E)200). 

Oxidation o( ketones to a-hydroxyketones by means of a peroxymolybdenum reagent. 

Ketone 20, derived in one uneventful step from hydroxyketone... 

Ketoesters, synthesis of 608, 615 Ketones - see also a-Cyanoketones, Hydroxyketones, Sulphinylketones synthesis of 811-814 y-Ketonitriles, synthesis of 322 /3-Ketosulphones... 

As an extension of this work, the same authors explored such methodology for the synthesis of 2,6-disubstituted dihydropyrans using secondary homopropargylic alcohols (Scheme 10, route E). Surprisingly, the treatment of pent-4-yn-2-ol and 3-methylbutanal in the presence of FeCls led to unsaturated ( )-(3-hydroxyketone and ( )-a,p-unsaturated ketone in 2.5 1 ratio and 65% yield, without any trace of the expected Prins-type cyclic product (Scheme 22) [36]. To test the anion influence in this coupling, FeCE and FeBrs were used in a comparative study for the reaction of pent-4-yn-2-ol (R = R" = H, = Me) and several aldehydes. A range of aldehydes except for benzaldehyde was transformed into unsaturated (3-hydroxy-ketones in moderate to good yields. 

Reduction of (3-hydroxy ketones through chelated TSs favors. yy -l,3-diols. Boron chelates have been exploited to achieve this stereoselectivity.129 One procedure involves in situ generation of diethylmethoxyboron, which then forms a chelate with the (3-hydroxyketone. Reduction with NaBH4 leads to the vyn-diol.130... 

The first intermediate product of ketone oxidation is a-ketohydroperoxide. All other molecular products are formed by decay and reactions of this hydroperoxide and its adduct with ketone. Among these products, aldehydes, diketones, a-hydroxyketones, acids, esters, and C02 were observed. The information about the products of the oxidation of ketones by dioxygen are available in monographs [4,7],... 

The 1,3-dipolar addition to terminal alkenes of nitrile oxides, generated from nitromethylene derivatives of bicycloheptane, provides 9,ll-ethano-13,15-isoxazolinoprostanoids, PGH analogs, with alkyl, phenyl, or additional heterocyclic fragment in the oo-chain (461). Chemical transformations of 9,11-ethano-13,15-isoxazolinoprostanoids furnish prostanoids with bifunctional fragments of P-hydroxyketone and a-aminoalcohol in the oo-chain. The reaction of P-hydroxy ketones with methanesulfonyl chloride gives rise to prostanoids with an enone component in the oo-chain. 9,ll-Ethano-16-thiaprostanoids have been prepared, for the first time, by nucleophilic addition of thiols to the polarized double bond in the oo-chain. The 1,3-dipolar addition to terminal alkenes of nitrile oxides, generated from nitromethylene derivatives of bicycloheptane provides 9,ll-ethano-13,15-isoxazolinoprostanoids with an alkyl, phenyl, or additional heterocyclic fragment in the oo-chain (462). 

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