Ketone Oxidation State

The hydrolysis has traditionally been performed with protic acids. Recently, however, transition metals have been used to facilitate the reaction. Frequently, with internal alkynes, a mixture of regioisomeric ketones are formed. 

1-Octyne (7.5 g) and formic acid (100 mL) were heated in an oil bath at 100 °C until all starting material was consumed. The progress of the reaction was monitored by GC analysis of the reaction solution. Quantitative GC analysis at the end of the reaction (6 h) indicated 92% yield of 2-octanone. The cooled reaction mixture was taken up with CH2C12 (170 mL), and the solution was washed with water, sodium carbonate solution, and water, dried over MgS04, and evaporated in vacuo. The residue was distilled (bp 171-173 °C) to give 2-octanone (7.42 g, 85%). 

To a stirred solution of the epoxide (3.50 g, 40.6 mmol) and CuCN (364 mg, 4.06 mmol) in dry THF (30 mL) was added a 1 M solution of vinylmagnesium bromide in THF (52.8 mL, 52.8 mmol), over 45 min, dropwise at -78 °C. The mixture was allowed to warm up to 0 °C before it was quenched with a saturated aqueous NH4C1 solution (20 mL). The layers were separated, the aqueous layer extracted with ether (3 x 50 mL), and the combined ethereal extracts were washed with brine (20 mL) and dried (MgS04). Evaporation of the solvent and chromatographic purification of the crude product (silica, Et20 pentane 1 3) gave the alcohol as a pale yellow oil (4.41 g, 95%). 

The most common ketals are dioxolane and dioxane these form more readily and have fewer problems with enol ether contamination. Sometimes, however, they can be difficult to hydrolyze, particularly when the molecule contains sensitive functional groups. The reaction is acid catalyzed, with some of the more common acids being para-toluenesulfonic, pyridinium para-toluenesulfonic, and camphorsulfonic. The eliminated water can be removed either with an azeotroping solvent (such as toluene or benzene) or by the addition of a dehydrating agent such as trimethylorthoformate. 

A solution of the ketone (1.23 g, 8.11 mmol), ethylene glycol (1.8 mL, 32 mmol), pyridinium tosylate (0.6 g, 2.4 mmol), and benzene (45 mL) was refluxed for 22 h in a Dean-Stark apparatus. The reaction mixture was cooled, poured into saturated NaHC03 (50 mL), the aqueous layer extracted with hexanes/Et20 (1/1, 2 x 20 mL), and washed with brine (2 x 15 mL). The combined organics were dried (MgS04), concentrated, and chromatographed to give the ketal (1.59 g, 100%). 

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Ritterazines H and I form another pair of C-22 epimers, with C-12 now at the ketone oxidation state and biological activity reduced by approximately twenty-fold. The presence of both 5/5 spiroketal diastereomers for a number of ritterazines implies that epimerization at C-22 is not energetically prohibitive. Interestingly, such spiroketal epimers have yet to be observed among the cephalostatins. 

Unlike the situation with the asterriquinones, a modular synthesis of illudins had already been developed through the efforts of Padwaand Kinder. The dipolar cycloaddition of a carbonyl yhde derived from a diazo-p-diketone with a cyclopentenone forms two C-C bonds and establishes the ring skeleton (Figure 9.7) in the key intermediate. The final carbon was added by a methyl Grignard addition to the more reactive ketone. Oxidation states and functional groups were adjusted to provide dehydroiUudin M, and it was converted to illudin M. 

There was essentially one main approach (with a number of buUt in fallback strategies) that was convergent in nature and relied heavily on an acyl anion equivalent (10) to introduce both halves (LHF 11 and RHF 12) and also acted as the spiroketal carbon center in the ketone oxidation state (i.e., 13). Ketone 13 could then be treated with acid to cyclize the linear precursor to EBC-23 (1), driven thermodynamically by the anomeric effect (Scheme 1). 

Actinide ions form complex ions with a large number of organic substances (12). Their extractabiUty by these substances varies from element to element and depends markedly on oxidation state. A number of important separation procedures are based on this property. Solvents that behave in this way are thbutyl phosphate, diethyl ether [60-29-7J, ketones such as diisopropyl ketone [565-80-5] or methyl isobutyl ketone [108-10-17, and several glycol ether type solvents such as diethyl CeUosolve [629-14-1] (ethylene glycol diethyl ether) or dibutyl Carbitol [112-73-2] (diethylene glycol dibutyl ether). 

Eithei oxidation state of a transition metal (Fe, Mn, V, Cu, Co, etc) can activate decomposition of the hydiopeioxide. Thus a small amount of tiansition-metal ion can decompose a laige amount of hydiopeioxide. Trace transition-metal contamination of hydroperoxides is known to cause violent decompositions. Because of this fact, transition-metal promoters should never be premixed with the hydroperoxide. Trace contamination of hydroperoxides (and ketone peroxides) with transition metals or their salts must be avoided. 

Many mercury compounds are labile and easily decomposed by light, heat, and reducing agents. In the presence of organic compounds of weak reducing activity, such as amines (qv), aldehydes (qv), and ketones (qv), compounds of lower oxidation state and mercury metal are often formed. Only a few mercury compounds, eg, mercuric bromide/77< 5 7-/7, mercurous chloride, mercuric s A ide[1344-48-5] and mercurous iodide [15385-57-6] are volatile and capable of purification by sublimation. This innate lack of stabiUty in mercury compounds makes the recovery of mercury from various wastes that accumulate with the production of compounds of economic and commercial importance relatively easy (see Recycling). 

Whenever we run a reaction that involves a decrease in oxidation state, we say that a reduction has occurred. For example, converting a ketone or aldehyde into an alcohol ... 

Earlier in this chapter, we learned definitions for the terms oxidation and reduction. We saw that oxidation involves an increase in oxidation state. For example, oxidation of a secondary alcohol will produce a ketone ... 

The oxidation by chromic acid alone leads to a mixture of cyclobutanone and 4-hydroxybutyraldehyde the existence of an isotope effect for the oxidation of I-deuteriocyclohexanol suggests that Cr(VI) produces the ketone and lower oxidation states of chromium produce the cleavage product. 

Recently, it has been demonstrated that coordination vacancies on the surface metal cations are relevant to the unique redox reactivity of oxide surfaces]2]. Oxidation of fonnaldehyde and methyl formate to adsorbed formate intermediates on ZnO(OOOl) and reductive C-C coupling of aliphatic and aromatic aldehydes and cyclic ketones on 1102(001) surfaces reduced by Ar bombardment are observed in temperature-prognunmed desorption(TPD). The thermally reduced 1102(110) surface which is a less heavily damaged surface than that obtained by bombardment and contains Ti cations in the -t-3 and +4 states, still shows activity for the reductive coupling of formaldehyde to form ethene]13]. Interestingly, the catalytic cyclotrimerization of alkynes on TiO2(100) is also traced in UHV conditions, where cation coordination and oxidation states appear to be closely linked to activity and selectivity. The nonpolar Cu20( 111) surface shows a... 

Tin enolates are also used in aldol reactions.27 Both the Sn(II) and Sn(IV) oxidation states are reactive. Tin(II) enolates can be generated from ketones and Sn(II)(03SCF3)2 in the presence of tertiary amines.28 The subsequent aldol addition is syn selective and independent of enolate configuration.29 This preference arises from avoidance of gauche interaction of the aldehyde group and the enolate P-substituent. The syn stereoselectivity indicates that reaction occurs through an open TS. 

The question about the competition between the homolytic and heterolytic catalytic decompositions of ROOH is strongly associated with the products of this decomposition. This can be exemplified by cyclohexyl hydroperoxide, whose decomposition affords cyclo-hexanol and cyclohexanone [5,6]. When decomposition is catalyzed by cobalt salts, cyclohex-anol prevails among the products ([alcohol] [ketone] > 1) because only homolysis of ROOH occurs under the action of the cobalt ions to form RO and R02 the first of them are mainly transformed into alcohol (in the reactions with RH and Co2+), and the second radicals are transformed into alcohol and ketone (ratio 1 1) due to the disproportionation (see Chapter 2). Heterolytic decomposition predominates in catalysis by chromium stearate (see above), and ketone prevails among the decomposition products (ratio [ketone] [alcohol] = 6 in the catalytic oxidation of cyclohexane at 393 K [81]). These ions, which can exist in more than two different oxidation states (chromium, vanadium, molybdenum), are prone to the heterolytic decomposition of ROOH, and this seems to be mutually related. 

Keeping in mind "generalisation 3" concerning the priority of the carbon skeleton over the oxidation state of the functional groups (or even of the carbon chain itself), the synthesis of a consonant molecule (or system) with n bonds between the two functional groups has, in principle, n possible different synthetic pathways. For instance, the 1,3-amino-ketone,... 

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