Cyclic diketone reductions

Intramolecular coupling Some aromatic diketones have been stereoselectively cy-clized under various electrolysis conditions, which, together with the substrate structure, strongly influence the stereochemistry of the formed cyclic diol. Reductive cyclization of 1,8-diaroylnaphthalenes led to trans-diols, 2,2 -diaroylbiphenyls and a, )-diaroylalkanes yielded cis-diols with different stereoselectivities depending on substrate structure and electrolysis conditions (pH, cosolvent) (Fig. 57) [310-312]. 

The enzyme catalyzing the reduction of ketopantolactone to D-pantolactone was isolated in a crystalline form from the cells of Candida parapsilosis and characterized in some detail [106] (see Tables 4 and 5). It is a novel NADPH-dependent carbonyl reductase with a molecular mass of about 40,000. In addition to the reduction of ketopantolactone, the enzyme catalyzes those of a variety of cyclic diketones, including derivatives of ketopantolactone, isatin, camphorquinone and so on, to give the corresponding (R)-alcohols [106, 107], The enzyme was termed conjugated polyketone reductase , since the enzyme catalyzes only the reduction of conjugated polyketones as follows. 

In order to reduce the crystallinity of the polyketal an unsymmetrical cyclic diketone was prepared from 2,7-dihydroxy-naphthalene. Reduction of the naphthalene nucleus with Raney nickel and hydrogen gave a 90% yield of the 2,7-decalindiol, which on oxidation with chromic acid gave a 50% yield of the 2,7-deca-lindione. When this diketone was condensed with the tetrakis-(hydroxymethyl) cyclohexane, an 89% yield of a white polymer VIII was obtained which did not melt and was soluble only in hexa-fluo ro isopropano1. 

Reductions of aromatic carbonyl compounds a-substituted carbonyl compounds a-hydroxy ketones p- and y-substituted carbonyl compounds ketones and a- and p-diketones P-keto acids and esters, y-kcto esters masked carbonyl compounds activated double bonds (hydrogenation) acyclic and cyclic ketones reductive amination of keto acids BY BY BY, glycerolDH BY BY, An, Cr, Cu, Gc, Ha, Ks, Mi, Mr, Ns, Pd, Pm, Rn, Y1 BY, Ao, Cb, Cg, Cu, Ct, Gc, Hp, Lk, Mj, Pf, Pm, Pv, Rr, Td, glycerolDH BY BY, An, Gc, Pc HLADH, TBADH, other ADHs, HSDHs AADH, GluDH, PheDH... 

Sodium carbonate 1,2,3-Triketones from / -diketones via 2-azo-, 2-amino-, 2-diazo-, and 2-hydroxy-1,3-diketones Cyclic trans-tixed -diketones Reduction of water-solubility... 

The quinones are a rather heterogeneous collection of compounds with structures based on an unsaturated system of cyclic diketones. The biologically important plastoquinones, ubiquinones, and vitamin K are included in this group however, as pigments the most widespread and important quinones are the 1,4-naphthaquinones (Fig. 18) and the 9,10-anthraquinones (Fig. 19, Table 10). Methyl, methoxyl, and hydroxyl groups are the most common substituents, and O- and C-glycosides (see Fig. 20) are frequently present in the anthraquinone group. Several structural modifications exist due to reduction, dimerization (Fig. 21), and addition of side chains. 

Diketimines can be prepared by condensation of 1,2-diketones with 2 equiv of an amine, or 1 equiv of a 1,2-diamine, by azeotropic removal of water. Either a chiral diketone or a chiral amine/diamine can be used in order to obtain a chiral diimine. In both cases, the use of 1,2-diamines is expected to provide better stereocontrol, because of the rigidity of the derived cyclic diimines. For example, the reaction of camphor 1,2-diketone 275 and racemic 1,2-diphenylethylenediamine (d,l)-26 gave the diimine 276 as a mixture of two diastereomers (Scheme 45) [138]. Reduction of 276 with sodium borohydride followed by hydrogenolysis of the N substituents afforded the camphordiamine, which was isolated as the dihydrochloride... 

It is possible to form cyclic ethers from diketones as seen by the cyclic hemike-tal formed by the reduction of 1,5-cyclooctanedione (Eq. 228) and the conversion of 2,5-hexanedione into cis- and /ran.v-2,5 -di me(In Itetrahydrofuran (Eq. 229).392 A naphthopyran can be formed in a similar manner.339... 

Diketones are reductively cyclized in a TFA-catalyzed reaction. The cycliza-tion of the cage structure shown in Eq. 236 illustrates this ring closure in the formation of an acetal of trifluoroacetaldehyde.409 The organosilane reduction of triketone 69 followed by Jones oxidation gives the cyclic ketoether in fair yield (Eq. 237).410... 

A total synthesis of functionalized 8,14-seco steroids with five- and six-membered D rings has been developed (467). The synthesis is based on the transformation of (S)-carvone into a steroidal AB ring moiety with a side chain at C(9), which allows the creation of a nitrile oxide at this position. The nitrile oxides are coupled with cyclic enones or enol derivatives of 1,3-diketones, and reductive cleavage of the obtained cycloadducts give the desired products. The formation of a twelve-membered ring compound has been reported in the cycloaddition of one of the nitrile oxides with cyclopentenone and as the result of an intramolecular ene reaction, followed by retro-aldol reaction. 

The lower members of the homologous series of 1. Alcohols 2. Aldehydes 3. Ketones 4. Acids 5. Esters 6. Phenols 7. Anhydrides 8. Amines 9. Nitriles 10. Polyhydroxy phenols 1. Polybasic acids and hydro-oxy acids. 2. Glycols, poly-hydric alcohols, polyhydroxy aldehydes and ketones (sugars) 3. Some amides, ammo acids, di-and polyamino compounds, amino alcohols 4. Sulphonic acids 5. Sulphinic acids 6. Salts 1. Acids 2. Phenols 3. Imides 4. Some primary and secondary nitro compounds oximes 5. Mercaptans and thiophenols 6. Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides 7. Some diketones and (3-keto esters 1. Primary amines 2. Secondary aliphatic and aryl-alkyl amines 3. Aliphatic and some aryl-alkyl tertiary amines 4. Hydrazines 1. Unsaturated hydrocarbons 2. Some poly-alkylated aromatic hydrocarbons 3. Alcohols 4. Aldehydes 5. Ketones 6. Esters 7. Anhydrides 8. Ethers and acetals 9. Lactones 10. Acyl halides 1. Saturated aliphatic hydrocarbons Cyclic paraffin hydrocarbons 3. Aromatic hydrocarbons 4. Halogen derivatives of 1, 2 and 3 5. Diaryl ethers 1. Nitro compounds (tertiary) 2. Amides and derivatives of aldehydes and ketones 3. Nitriles 4. Negatively substituted amines 5. Nitroso, azo, hy-drazo, and other intermediate reduction products of nitro com-pounds 6. Sulphones, sul-phonamides of secondary amines, sulphides, sulphates and other Sulphur compounds... 

Only the 2,2 - and 4,4 -bipiperidyl (2) were reported at that time however, later studies report the 2,4 -isomer as one of the products.29 Recent work suggests that acidic reduction of pyridine gives not only 4,4 -bipyridine (1) as well as 2,2 -(l) and bipiperidyl (2), but also the diketone (3).30 The structure of this product is apparently in error because the authors report a carbonyl stretching frequency (1400-1590 cm-1) that is inconsistent with a cyclic ketone. The calculated m/e peaks are incorrect, and the reported fragmentation pattern is unexpected. A better formulation of this material would perhaps be an open-chain structure. 

Quinones are cyclic conjugated diketones. They are colored compounds used as dyes. They also play important roles in reversible biological oxidation-reduction (electron-transfer) reactions. 

Fig (14) Olefin (107) has been converted to cyclic ether (114) by standard reactions. Its transformation to enone (115) is accomplished by annelation with methyl vinyl ketone and heating the resulting diketone with sodium hydride in dimethoxyethane. The ketoester (116) is subjected to Grignard reaction with methyllithium, aromatization and methylation to obtain the cyclic ether (117). Its transformation to phenolic ester (119) has been achieved by reduction, oxidation and esterification and deoxygenation. 

Quinones are cyclic unsaturated diketones in which the carbon atoms are derived from the oxidation of an aromatic system. Although the underlying reactivity of quinones is that of unsaturated ketones (cyclohexadi-enediones), it is tempered by this relationship to aromatic compounds and in particular by their reduction to dihydroxyphenols (quinols). 

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