Cyclic ketones, oxidation

Oxidation of tim5-4-(2,2,2-tnfluoro-l-hydroxy 1 tnfluoromethylethyl)cyclo-hexanol with pyridinium chlorochromate results m the correspondmg cyclic ketone whereas oxidation with nitnc acid m the presence of a catalyst causes ring cleavage [50] (equation 46)... 

The effect of the nitric acid/hydrogen peroxide mixture on acetone when it is hot gives rise to an explosive oxidation, especially when the medium is confined. This situation also applies to a large number of ketones, and in particular, cyclic ketones. Cyclic di- and triperoxides form compounds that detonate, if there is no strict and very delicate thermal control. Accidents have been reported with butanone, 3-pentanone, cyclopentanone, cyclohexanone and methylcyclo-hexanones. 

Acetalization of l-alkenes. The Wacker uinversion of l-alkenes to methyl ketones by oxidation catalyzed by PdCE-CuCl takes a different course when applied to vinyl ketones (1). Thus oxygenation of mixtures of I and 1,3- or 1,2-diols catalyzed by PdCE-CuCl results in cyclic acetals formed by exclusive attaek at the terminal carbon atom. A similar reaction occurs with l-alkenes substituted with COOCH,. 

Esters have been prepared in 63-73% yields from several simple cycloalkyl and aryl alkyl ketones by reaction at room temperature with per-benzoic acid. The larger radical of the ketone appears as the alcohol fragment of the ester. Cyclic ketones are oxidized by potassium persulfate and sulfuric acid to esters from which o>-hydroxy aliphatic esters are obtained upon hydrolysis and reesterification. Peracetic acid in acetic anhydride converts salicylaldehyde to o-hydroxyphenyl formate (88%). ... 

Behari et al. (1982b) find that ceric oxidation of cyclohexanone and methylcyclohex-anone in sulfuric acid solutions do conform to the Michaelis-Menten rate law. By comparing the rate of oxidation with that for enolization (determined by reaction rate for the substrate with iodine), the authors establish that the reaction must involve the ketonic form of the substrate. Earlier results reported by Benson (1976) agree with this assessment and suggest further that a C-H bond is broken in the rate-determining step. The authors are unable to resolve the rate and equilibrium parameters for electron transfer and precursor complex stability. The cyclic ketones are oxidized nearly an order of magnitude faster and under milder conditions than the aliphatic ketones. 

Similarly, VOCs adsorbed from air samples onto Tenax or activated charcoal can be sealed and stored for several months prior to analysis. Losses have been reported only with cyclic and aliphatic ketones (catalytic oxidation) and esters (hydrolysis) [ 14.5]. For these groups of substances, losses approach a maximum of 20 % after a four-week storage period. No losses were observed with benzene, toluene, and xylenes over a 24-month storage period [146]. Samples containing analytes of lower volatility can be stored in suitable containers for a few days at -i4 °C, and for several months deep-frozen at -18 °C or lower. 

Cyclic ketones were oxidized to the corresponding dicarboxylic acids, via initial Baeyer-ViUiger reaction, using hydrogen peroxide in the presence of a catalyst comprising 1 mol%... 

Permaleic acid is an excellent reagent for the Baeyer-Villiger reac-In the latter, an acyclic or a cyclic ketone is oxidized to the... 

Methylenation of carboxylic acid derivatives A variety of carboxylic acid derivatives can be transformed into heteroatom-substituted olefins (Table 4.9). The C-glycoside congeners are easily prepared by the direct methylenation of aldono-lactones with 30 (entry 2) [67]. Since the generation of titanocene-methylidene 4 from 30 only produces methane as a by-product, 30 can be employed for the olefination of acid-sensitive substrates such as silyl esters and acylsilanes (entries 4 and 6). The tolerance toward acid-sensitive functional groups also allowed the application of dimethyltitanocene 30 in the conversion of a lactone bearing an acetal moiety into the corresponding cyclic vinyl ether, which was further transformed into the spiroketal ketone upon oxidation and rearrangement (Scheme 4.24) [69]. 

Ketones may be oxidized to esters by peracids or hydrogen peroxide, a process known as the Baeyer-Villiger oxidation. Unsymmetric ketones are oxidized selectively at the more substituted a carbon and that carbon migrates to oxygen with retention of configuration. Trifluoroperacetic acid generated in situ gave the double example in Equation 6.9 [14]. Cyclic ketones afford lactones (Eq. 6.10) [15]. 

The first exploitation of microbial BVase to produce chiral lactones from cyclic racemic bicyclo[2.2.1]hept-2-en-7-ones (Fig. 10) was reported by Ouazzani et al. [17]. A report of preparative scale bioconversion of cyclic ketone was made [26]. The preparative scale bioconversion of using Acinetobacter TD 63 provides lactones in high optical purity [27]. Subsequently [28], whole-cell bioconversions of bicyclic lactones was made, using Acinetobacter sp. NCIB 9871 and Pseudomonas sp. NCIB 9872 to produce file same chiral synthons. In all cases, the racemic ketone was oxidized, and equal amounts of the regioisomeric lactones (—)-(i5, 5/ )-2-oxabicyclo[3.3.0]oct-6-en-3-one and (—)-(iR,55)-3-oxabicyclo[3.3.0]oct-6-en-3-one were produced in high enantiomeric purity. 

The oxidation of the cyclic enol ether 93 in MeOH affords the methyl ester 95 by hydrolysis of the ketene acetal 94 formed initially by regioselective attack of the methoxy group at the anomeric carbon, rather than the a-alkoxy ketone[35]. Similarly, the double bond of the furan part in khellin (96) is converted ino the ester 98 via the ketene acetal 97[l23],... 

The 3.8-nonadienoate 91, obtained by dimerization-carbonylation, has been converted into several natural products. The synthesis of brevicomin is described in Chapter 3, Section 2.3. Another royal jelly acid [2-decenedioic acid (149)] was prepared by cobalt carbonyl-catalyzed carbonylation of the terminal double bond, followed by isomerization of the double bond to the conjugated position to afford 149[122], Hexadecane-2,15-dione (150) can be prepared by Pd-catalyzed oxidation of the terminal double bond, hydrogenation of the internal double bond, and coupling by Kolbe electrolysis. Aldol condensation mediated by an organoaluminum reagent gave the unsaturated cyclic ketone 151 in 65% yield. Finally, the reduction of 151 afforded muscone (152)[123]. n-Octanol is produced commercially as described beforc[32]. 

The November 2001 issue of the Journal of Chemical Education ipp 1533-1534) describes an introductory biochemistry laboratory ex periment involving cycio hexanone monooxygenase oxidation of cyclic ketones... 

Compounds known as lactones which are cyclic esters are formed on Baeyer—Vilhger oxi dation of cyclic ketones Suggest a mechanism for the Baeyer—Vilhger oxidation shown... 

Methyl ketones are important intermediates for the synthesis of methyl alkyl carbinols, annulation reagents, and cyclic compounds. A common synthetic method for the preparation of methyl ketones is the alkylation of acetone derivatives, but the method suffers limitations such as low yields and lack of regioselectivity. Preparation of methyl ketones from olefins and acetylenes using mercury compounds is a better method. For example, hydration of terminal acetylenes using HgSO gives methyl ketones cleanly. Oxymercuration of 1-olefins and subsequent oxidation with chromic oxide is... 

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