Reduction cyclic ketones

Ketones, Cyclic and Bicydic, Reduction of, by Complex Metal Hydrides/Boone and Asfttiy/ 11 53... 

The starting material for the present synthesis was Wieland-Miescher ketone (24), which was converted to the known alcohol (25) by the published procedure [10], Tetrahydropyranylation of alcohol (25) followed by hydroboration-oxidation afforded the alcohol (26), which on oxidation produced ketone (27). Reduction of (27) with metal hydride gave the alcohol (28) (56%). This in cyclohexane solution on irradiation with lead tetraacetate and iodine produced the cyclic ether that was oxidized to obtain the keto-ether (29). Subjection of the keto-ether (29) to three sequential reactions (formylation, Michael addition with methyl vinyl ketone and intramolecular aldol condensation) provided tricyclic ether (30) whose NMR spectrum showed it to be a mixture of C-10 epimers. The completion of the synthesis of pisiferic acid (1) did not require the separation of epimers and thus the tricyclic ether (30) was used for the next step. The conversion of (30) to tricyclic phenol (31) was... 

Reduction of ot-keto epoxides. Epoxidation of cyclic allylic alcohols results mainly in the epoxide syn to the hydroxyl group (4, 76). Schlessinger et al. have reported a method for isomerization of the alcohol group by oxidation to the ketone and reduction to the anh-alcohol. In a model case, 2->4, pyridinium chloro-chromate buffered with sodium acetate was found to be the most satisfactory oxidant. Stereoselective reduction to 4 was found to be a more difficult problem, but eventually triisobutylaluminum was found to effect this reduction in high yield. 

Reduction of cyclic ketones. Competitive reductions of cyclic ketones of various types with lithium tri-/-butoxyaluminum hydride indicate that nonconjugated cnones are less reactive than cyclic staturaled ketones, but more reactive than conjugated cnones. Steric effects do not appear to be important, since 3-ketocyclohe ene (1) is less... 

Tilborg and coworkers " recently reported an extensive study concerning the electrosynthesis of cyclopropanone adducts from either a,a -dibromo ketones or from a,a -dibromo- and a,a -dichloro-carbonyl protected ketones. With the non-protected ketones the reductions were carried out in MeCN in the presence of various nucleophiles (Table 2). It was found that the yields of cyclopropanone adducts decrease when the dihaloketone becomes less substituted, due to a competing side reaction in which a bromide is displaced by the nucleophile. Furthermore, in the presence of excess of added protic nucleophile the yields of the cyclic products decrease due to a competing protonation of the anionic intermediate. 

Ipc)2BCl [from (+)-a-pinene] and (+)-(Ipc)2BCl [from (-)-a-pinene] are excellent reagents for the enantioselective reduction of aryl- and alkyl ketones, cyclic ketones, a-keto esters " , and a,(3-unsaturated ketones. " ... 

Dihydroxy allenes are generated from ketoenes and ethynyl epoxides. a,P-Epoxy ketones undergo reductive cleavage but the P-hydroxy ketones thus obtained can react further, for example with an e, -double bond to give cyclic 1,3-diols. Note that the double bond does not have to be activated, and furthermore, a silylalkyne moiety and a tricarbonylchromium-complexed arene can play the same role, although in the latter case the net result is a cine-substitution. 

Cycloaliphatic amine synthesis routes may be described as distinct synthetic methods, though practice often combines, or hybridizes, the steps that occur amination of cycloalkanols, reductive amination of cyclic ketones, ring reduction of cydoalkenjiamines, nitrile addition to ahcycHc carbocations, reduction of cyanocycloalkanes to aminomethylcycloalkanes, and reduction of nitrocydoalkanes or cyclic ketoximes. 

KETONE, CONJUGATE ALLYLATION OF a,g-UNSATURATEO. 62, 86 KETONE, a-TERT-AUYLATION, 62. 95 Ketones, a,6-acetylen1c, asymnetrlc reduction, 63, 63 Ketones, cyclic, lactams from, 63, 188 Ketones, e-hydroxy-, synthesis of, 63, 79... 

Expoxidation of alkenes. In the presence of this complex, alkenes undergo epoxidation with oxygen (oxidant) and cyclic ketones as reductant. The most useful reductant is 2-methylcyclohexanone. Yields are 80% for trisubstituted or exo-terminal alkenes. 

Figure 15.16 summarizes a series of optically active alcohols and amines reported (in a review by Blacker at Avecia ) to be produced by the CATHy catalysts. These include the types of products described for the different classes of hydrogenations described in the previous sections. These products include those from the reduction of alkyl aryl ketones, a-ketoesters, aliphatic ketones, a,(3-unsaturated ketones, cyclic ketones, and a-hydroxy ketones. In addition, transfer hydrogenation allows for the asymmetric formation of amines by the reduction of N-diphenylphosphinylimines. These transfer hydrogenations... 

Cyclic alcohols from cyclic ketones Stereospecific reduction... 

An electrochemical counterpart to this cyclization is provided by the anodic reduction of non-conjugated olefinic ketones cyclic tertiary alcohols are formed (Scheme 101) in a process initiated by electron addition to the carbonyl group. This method is limited to cases leading to formation of five-and six-membered rings it provides some interesting stereochemical results, e.g, the isolation of cw-l,2-dimethylcyclopentan-l-ol, whereas methyl-magnesium iodide on 2-methylcyclopentanone gives mainly the trans-di-methyl isomer. 

Sulphur dioxide has been found to be a convenient catalyst for the formation of both cyclic and acyclic thioacetals. Nitromethyl ketones undergo reductive thioacetalization with ethanethiol and aluminium chloride, giving the thioacetal of the methyl ketone. ... 

Although five- and six-carbon monosaccharides exist predominately as hemiacetals and hemiketals, they undergo the characteristic reduction and oxidation reactions of simple aldehydes and ketones. The reduction or oxidation reaction occurs by way of the carbonyl group in the small amount of the open-chain form of the monosaccharide in equilibrium with its cyclic hemiacetal or hemiketal. As the reduction or oxidation occurs, the equilibrium shifts to produce more of the carbonyl form until eventually all the monosaccharide reacts. 

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