Carbonyl compounds useful transformations

Examples for the oxidation of carbonyl compounds using halide ions as redox catalyst are listed in Table 4. No. 47-50. Thus, in the presence of alcohols, aldehydes are transformed to esters (No. 47)... 

It has been shown that monosubstituted enolates can be transformed selectively to give a-fluoro and a,a-difluoro carbonyl compounds using A-fluorosultam 3 in a one-pot procedure,10,11 154 158 e.g. formation of 6123 (see also Table 17159). 

Freshly prepared Mn02 is a useful reagent in organic chemistry and has been used in a large variety of oxidative transformations.311 These reactions involve the allylic oxidation of alkene to a,/3-unsaturated carbonyl compounds, the transformation of methylarenes to benzaldehyde and benzoic acid derivatives, the oxidation of secondary methylene groups to ketones, and the oxidation of alcohols to carbonyl compounds.311 The yields are generally fair to good. 

Various types of structures 895 and 896 were obtained with use of transformation (4.58) applied to iminoalcohol derivatives of heterocyclic carbonyl compounds used as ligands [220,225], The structure of 895 [225] and 896 [220] was proved by x-ray analysis ... 

Illustrated in Table III are the solvent effects. The carbonyl compound used is a-phenylpropionaldehyde and the optically active acid is D-camphorsulfonic acid. The figure reveals that when hydrolysis is carried out, less miscible solvents are more effective suggesting that interfacial reactions are effective for stereoselectivity of asymmetric transformations. 

H.J. Bestmann has prepared the phosphazine of TFAE from 18 and triphenyl phosphine. This compound is hydrolyzed by ZnCl2/H20 to give the parent hydrazone 22 and it can be transformed to the corresponding tris carbonyl compound using HN02 (ref. 41). In analogy to the studies by H. Neuenhoffer, we have N-acylated 22 by acid anhydrides to obtain crude N-acylhydrazones 211 in about 50 % yield (Scheme 46). 

The production of antibiotics and steroids is mainly based on the Baeyer-Villiger oxidation. This synthetic route is an oxidative transformation of carbonyl compounds using a strong oxidant such as a peroxyacid. The transformation of an acyclic ketone to an ester is shown by the following scheme ... 

The introduction of an oxygen atom at a saturated position of benzylic halides transforms these compounds to carbonyl compounds. Using sodium hypochlorite under sonication, ketones are obtained in good yields (>88%) from secondary halides, but a mixture of aldehyde and acid are formed from primary halides. 

The usual base or acid catalyzed aldol addition or ester condensation reactions can only be applied as a useful synthetic reaction, if both carbonyl components are identical. Otherwise complicated mixtures of products are formed. If two different aldehydes or esters are to be combined, it is essential that one of the components is transformed quantitatively into an enol whereas the other component remains as a carbonyl compound in the reaction mixture. 

There has been recent interest in naphtho-fused dithiepines as chiral acyl anion equivalents, particularly since the starting dithiol 128 can be obtained in enan-tiomerically pure form (89TL2575). This is transformed using standard methods into the dithiepine 129, but showed only moderate diastereoselectivity in its addition to carbonyl compounds. On the other hand, as we have seen previously for other systems, formation of the 2-acyl compound 130 and reduction or addition of a Grignard reagent gave the products 131 with much better stereoselectivity (91JOC4467). 

Novel aerobic oxidation method using A-hydroxyphthalimide as a catalyst (transformations of hydrocarbons to alcohols and/or carbonyl compounds) 99YGK24. 

The required nitrite esters 1 can easily be obtained by reaction of an appropriate alcohol with nitrosyl chloride (NOCl). The 3-nitroso alcohols 2 formed by the Barton reaction are useful intermediates for further synthetic transformations, and might for example be converted into carbonyl compounds or amines. The most important application for the Barton reaction is its use for the transformation of a non-activated C-H group into a functional group. This has for example been applied for the functionalisation of the non-activated methyl groups C-18 and C-19 in the synthesis of certain steroids. ... 

The most generally useful method for preparing alkyl halides is to make them from alcohols, which themselves can be obtained from carbonyl compounds, as we ll see in Sections 17.4 and 17.5. Because of the importance of the process, many different methods have been developed to transform alcohols into alkyl halides. The simplest method is to treat the alcohol with HC1, HBr, or HI. For rea-... 

Reaction of optically active a-sulphinyl acetate 298a with prochiral carbonyl compounds proceeds with a high asymmetric induction - , the degree of which depends on the nature of substituents at the carbonyl group (equation 252 Table 22) . The jS-hydroxy sulphoxides 422 formed may be transformed to optically active p-hydroxycarboxylic esters 423 (equation 253) and optically active long-chain lactones 424 99 (equation 254). Corey and coworkers have used this method to introduce a chiral centre at C-3 in their synthesis of maytansin °°, and Papageorgiou and Benezra for the synthesis of chiral a-hydroxyalkyl acrylates 425 ° (equation 255). 

For internal olefins, the Wacker oxidation is sometimes surprisingly regioselective. By using aqueous dioxane or THF, oxidation of P,y-unsaturated esters can be achieved selectively to generate y-keto-esters (Eq. 3.18).86 Under appropriate conditions, Wacker oxidation can be used very efficiently in transforming an olefin to a carbonyl compound. Thus, olefins become masked ketones. An example is its application in the synthesis of (+)-19-nortestosterone (3.11) carried out by Tsuji (Scheme 3.5).87... 

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117).331 Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, (i-unsaturated carbonyl compounds in aqueous acetic acid.332 Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid.333 Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

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