Hydroxy Ketones and Diketones

DMSO, molybdenum peroxide, benzene, reflux, 7-20 h, 60% yield. This method was used to m onoprotect 1,2-diols. The method is not general because oxidation to a-hydroxy ketones and diketones occurs with some substrates. On the basis of the mechanism and the results it would app>ear that overoxidation has a strong conformational dependence. 

LiInH4 is increased by the introduction of phenyl group(s) LiPhInH3 and LiPh2InH2 readily reduce aldehydes, ketones, acid chlorides, and even esters to the corresponding alcohols. Hydroxy ketones and diketones are reduced with lithium indium hydride to give meso-diols selectively. a-Hydroxy ketones and a-diketones are reduced to meso-1,2-diols with high diastereoselectivities, whereas the selectivities of /3-hydroxyketones and /3-diketones are less satisfactory.365... 

Reduction. Besides the reduction of carbonyl compounds with Bu3SnH to alcohols in hydroxylic solvents (e.g., MeOH), that of hydroxy ketones and diketones in dichloromethane in the presence of BF3 OEt2 is particularly interesting due to high stereoselectivity. 

The above appears to be a general reaction for converting a-hydroxy ketones into diketones in excellent yield thus furoin and anisoin give furil and anisil respectively. The reaction is probably ... 

Products detected or isolated from these oxidations include the corresponding a-hydroxy ketone and a-diketone and also adipic acid (from cyclohexanone) in up to 95 % yield. However, IrCI gives a-chloroketone in quantitative yield . Evidently when the rate of oxidation exceeds enolisation attack is on the keto form, probably via a complex, although this is definite only for Ce(IV) perchlorate, to give a radical, e.g. 

Utsukihara, T., Nakamura, H., Watanahe, M. and Horiuchi, C.A., Microwave-assisted synthesis of a-hydroxy ketone and a-diketone and pyrazine derivatives from a-halo and a,a -dibromo ketone. Tetrahedron Lett., 2006, 47, 9359. 

Permanganate oxidations may be used for the direct conversion of olefins to a-hydroxy ketones and 1,2-diketones in moderate yields usually under acidic conditions.562"566... 

Thallium trinitrate, TI(N03)3 3H20 (mp 102-105 C), oxidizes phenols and dihydroxy aromatic compounds to quinones [409, acetylenes to a-hydroxy ketones, a-diketones, or carboxylic acids 413] and methyl ketones to a-keto acids [414],... 

The Baeyer-Villiger reaction of hydroxy ketones and unsaturated diketones is very common in steroids, where it occurs preferentially at the keto group on C-17 and leaves the carbonyls in position 3 intact. 

Oxidations of hydroxy ketones to diketones occur frequently in steroidal alcohols. If the alcoholic group, usually secondary, is remote enough from the keto group, its oxidation takes place independently and is achieved by the same reagents that are used for the oxidation of alcohols. A solution of chromium trioxide in aqueous sulfuric acid oxidizes 5-pregnen-3p-ol-20-one in acetone solution at room temperature within 2-5 min to 5-pregnen-3,20-dione in 90% yield [579]. Similarly, lip-hydroxytestosterone 17-acetate is transformed by chromium trioxide in 80% acetic acid at room temperature in 30 min into 11-ketotestosterone 17-acetate in 92% yield [807]. 

The yeast reduction method has been applied with considerable success, notably by Neuberg and Levene and their associates, to several ample ketones, as well as to a few diketones and many hydroxy ketones and hydroxy aldehydes, - - the... 

The most systematically investigated acyl anion equivalents have been the IMS ethers of aromatic and heteroaromatic aldehyde cyanohydrins, TBDMS-protected cyanohydrins, - benzoyl-protected cyanohydrins, alkoxycaibonyl-protected cyanohydrins, THP-protected cyanohydrins, ethoxyethyl-protect cyanohydrins, a-(dialkylamino)nitriles, cyanophosphates, diethyl l-(trimethylsiloxy)-phenyimethyl phosphonate and dithioacetals. Deprotonation di these masked acyl anions under the action of strong basie, usually LDA, followed by treatment with a wide varies of electrophiles is of great synthetic value. If the electrophUe is another aldehyde, a-hydroxy ketones or benzoins are formed. More recently, the acyl caibanion equivalents formed by electroreduction of oxazolium salts were found to be useful for the formation of ketones, aldehydes or a-hydroxy ketones (Scheme 4). a-Methoxyvinyl-lithium also can act as an acyl anion equivalent and can be used for the formation of a-hydroxy ketones, a-diketones, ketones, y-diketones and silyl ketones. - - ... 

The benzoin condensation has recently been recognized as belonging to the general class of reactions that involve masked acyl anions as intermediates. For example, an aldehyde is converted into an addition product RCH(OX)Y, which renders the C—H acidic. Then under basic conditions, a masked acyl anion (see 1) can be formed and may react with an electrophilic component E. Decomposition of the product RCE(OX)Y should regenerate the carbonyl group with formation of RC(0)E. Intermediates such as (1) are us in the conversion of aldehydes into a-hydroxy ketones, a-diketones and 1,4-dicarbonyl compounds, proving to be a powerful strategy in the development of new synthetic methods. ... 

Oxidative opening of siloxycyclopropanes. Tertiary cyclopropanol systems undergo ring cleavage with a catalytic amount of VOfacaclj under oxygen to furnish 3-hydroxy ketones and 3-diketones. 

Similarly, reduction of 1,3-diketones with zinc and aqueous hydrochloric acid leads to intermediary cyclopropanediols that are transformed to unrearranged )8-hydroxy ketones and rearranged a-hydroxy ketones by cleavage of C-C bonds a and b, respectively, e.g. Scheme 5 (cf. Houben-Weyl, Vol.4/lc, pp 720-723, 73i 732).57-59,6i,63-69... 

Table 5. 2-Hydroxy Ketones and 1,2-Diols by Hydrogenation of 1.2-Diketones in the Presence of a Cobalt or Ruthenium Catalyst...

A few facts are also known concerning the metabolism of alkanes by plants. Cuticular waxes typically contain secondary alcohols, ketones and ) -diketones in addition to alkanes and the former have the skeletons as in Figure 8, where functionalization is near the centre of the molecule and the chain lengths of the alcohols and ketones are closely similar to those of the major n-alkanes present in any particular species. Tracer evidence indicates that the secondary alcohol and ketone are formed in sequence by oxidation of the corresponding n-alkane by a mixed function oxidase which is inhibited by chelating agents. Thus in Brassica species, the 14- or 15-hydroxy- and oxo-derivatives of the n-C29 alkane were thus formed both in vivo and in cell-free extracts ". ... 

This chapter explores several different carbon-carbon bond-forming reactions that lead to a variety of functionalized molecules diketones, hydroxy-ketones and hydroxy-aldehydes, keto-esters, keto-aldehydes, keto-nitriles, cyano-esters, hydroxy-nitriles, and cyano-aldehydes and cyano-ketones. The reactions that form these products may be categorized by defining the relevant disconnection. 

Waxes in general can contain a wide range of different compounds, including aliphatic diols, free alcohols, hydrocarbons (especially squalene), aldehydes, ketones, hydroxy-ketones, p-diketones and sesquiterpenes. The composition and biochemistry of waxes in nature, and methods for their analysis, have been reviewed in a comprehensive monograph [491],... 

Natural waxes can consist of a wide range of different lipid classes, including esters of various kinds, hydrocarbons, ketones, hydroxy-ketones, p-diketones, aldehydes, acids and terpenes. With cmde mixtures of this kind, it is usually necessary to react them with diazomethane to methylate free carboxyl groups, to acetylate (or to prepare TMS... 

Simple alkynes cannot be hydrated with a palladium catalyst, but triple bonds are hydrated regioselectively to yield ketones with participation of suitably located carbonyl or hydroxy groups. 1,5-Diketones are prepared by the participation of a 5-keto group (eq 58). 4-Hydroxyalkynes are converted to 4-hydroxy ketones and then oxidized to 1,4-diketones (eq 59). ... 

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