1.2- Diketones alicyclic

Aromatic esters may be used to aroylate the dianions derived from 1,3-diketones by reaction with potassium amide (60JOC538). Not only are acetyl and benzoyl acetones suitable for reaction, but alicyclic diketones and 2-hydroxyacetophenone are also acceptable. Cycliz-ation of the triketones occurs in cold sulfuric acid, presumably via the enolic form and the hemiacetal (Scheme 132). 

Enolate additions to p-halovinyl sulfones (289a) show synthetic promise notable is the procedure, by Metcalf, for vinylation of a-amino acid derivatives, e.g. (289a — 317 — 318).220 Recently, Ban reported that alicyclic ketone enolates add to the acetyl cation equivalent (319) to afford 1,3-diketones (Scheme 98).22(" In general, (3-halovinyl sulfones are synthetically superior to the (3-halovinyl sulfoxides. 

The following tables are intended to include all the reductions with aluminum alkoxides which were reported prior to February, 1943, although some examples doubtless have been overlooked. Table I lists the reduction of aldehydes, which have been subdivided into (a) aliphatic aldehydes and (b) alicyclic and aromatic aldehydes. Table II lists the reduction of ketones, which have been classified as (a)-satu-rated and unsaturated aliphatic ketones, (b) aromatic ketones, (c) alicyclic ketones, (d) unsaturated alicyclic and aromatic ketones, (e) a- — halogen substituted ketones, (f) diketones, (g) protected diketones, (h) alcoholic and phenolic ketones (and ethers or esters of these), and (i) keto esters. 

Ohashi. M., Takahashi. T.. Inoue, S and Sato. K., The Mannich reaction of alicyclic a-diketones. A novel synthesis of 2-hydroxy-.3-methyl-2-cyclohexcn-l-one, Bull. Chem. StK-. Jpn.. 48, 1892, 1975. 

This reaction is exhibited by a number of alkyl and alkoxy benzils, phenanthraquinone, and certain aliphatic and alicyclic a-diketones. 

Dihydrazones (readily available from 1,2-diketones) yield acetylenes on oxidation with a variety of oxidizing agents (equation 110). The method is applicable to aliphatic, alicyclic and aromatic dihydrazones. Recently it has been successfully applied in the preparation of cycloalkynes. 

Reduction of enol ethers or enol esters of 1,3-diketones, followed by acid-catalyzed allylic rearrangement of the reduction product (see p. 85 in ref. 5) is a useful route to a,P-unsaturated ketones. Ali-phatic - and alicyclic enones have thus been prepared in good yields at low temperatures with NaAlH2(0CH2CH20Me)2.2 6... 

This reaction has been used for the synthesis of a large variety of aldehydes and ketones - including (i) deuterio aldehydes (ii) optically active aldehydes and ketones (iii) alicyclic (Scheme 60, entry d) and cyclic diketones (Scheme 60, entry including those derived from... 

The ring contraction rearrangement of alicyclic a-diketones is much more valuable from the synthetic viewpoint e.g. equation 4). There are several routes available for the synthesis of a-diketones from monoketones. These include direct oxidation using selenium dioxide permanganate or osmium tetrox-ide addition across the double bond of an enone followed by base-promoted elimination of water bromi-nation to give the dibromo ketone followed by hydrolysis condensation with 4-nitroso-/V,/V-dimethylaniline followed by acidic hydrolysis — but there are many others. The bromination-hydrolysis route has been extensively studied by Wallach." The conversion of menthone into 1-hydroxy-... 

The products (4) derived from alicyclic ketones are useful for synthesis of spiro compounds. For example, the product (5) obtained from cyclohexanone has been transformed in several steps into the spiro enone (6) and into the spiro diketone (7). 

The synthesis of alicyclic 1,3-diketones from 7- or 6-keto esters is a well-established reaction. Over SO examples are tabulated in the 1954 chapter in Organic Reactions, and a similar number are tabulated as involving a Michael addition of a diester or keto ester to an unsaturated ketone followed by a Claisen condensation. These latter reactions involve such well-known syntheses as that of dimedone (S,S-di-methylcyclohexane-l,3-dione Scheme 75). 

Equally smooth is the reduction of aliphatic, alicyclic, and aromatic diketones to diols by the equivalent amount of complex boron hydrides. For instance, excellent yields of, mainly, m so-diols are obtained from acyclic 1,3-diols.389 The preparation of /ra .s-5-hydroxy-4a-methyl-zl1 8a-octalin-2-one from the corresponding dione by NaBN4390 is an example of selective reduction of one keto group of a dione ... 

Biphenyl and alicyclic derivatives. Phosphoric acids (117) catalyzed addition of j8-diketones, jS-ketoesters, and vinylogous amides to a,j8-unsaturated aldehydes to give substituted chromenones, pyranones, and tetrahydroquinolinones in good yields, under mild reaction conditions, via a formal [3 -h 3] cycloaddition (Scheme 28). ... 

In the continued search for retinoids with improved systemic tolerance, a variety of condensation products of retinaldehyde with aliphatic and alicyclic 1,3-diketones have been prepared (Acton and Brossi, 1980). Two representatives, the acetyl acetone and the dimedone derivative, have been prepared labeled with tritium (Kaegi et al., 1982c). As outlined in Fig. 15, dW-trans-retinol-11- H was produced by reduction of all- n -rctinoic-ll- H acid and then oxidized with manganese dioxide. HPLC of the resulting product showed... 

More than a third part of all the described principal syntheses of pyrimidines bearing fluorinated alkyl at C-4 atom commences from fluorinated p-dicarbonyl compounds 699. The chemistry of these bis-electrophiles was reviewed recently [411, 412] therefore, their preparation is not discussed herein. This synthesis of pyrimidines is fairly general (Table 34) it allows for introducing aliphatic, alicyclic and aromatic p-diketones (Entries 1-10), p-ketoesters (Entries 11-16), and cyclic P-ketoamides (Entry 17). Presence of some functional groups, such as additional ester moiety (Entry 15), is more or less tolerated, whereas increasing steric hindrance results in lowered yields of the products (Entry 10). A scope of conunon NCN binucleophiles include amidines (Entries 1, 11, 12, 17), (thio)urea and its derivatives (Entries 2-4), guanidines (Entries 5,16) and biguanides (Entry 6). Electron-rich amino heterocycles e.g. aminoazoles and even 2,6-diaminopyridine) are excellent NCN binucleophiles for the principal synthesis of fused pyrimidine derivatives (Entries 7-10, 13-15). 

Tautomeric Ratios Requiring Computation Alicyclic jl-Diketones 17... 

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