Ketones oxido

Acetic anhydride added to a mixture of NaB03 tetrahydrate and cyclohexene in methylene chloride at room temp, (slightly exothermic), and the mixture allowed to react for 16-24 h cyclohexene oxide. Y 75%. F.e., also glycol monoesters with H2SO4 as catalyst, s. G. Xie et al., Tetrahedron Letters 29, 2967-8 (1988) a,p-oxido-ketones under phase transfer catalysis (Na0H/(n-C6H,3)4N HS04 ) s. E.V. Dehm-low, B. Vehre, New J. Chem. 13, 117-9 (1989) glycol monoesters in acetic acid cf. 

Keto steroids can be obtained in excellent yields via the Beckmann degradation of 17a-hydroxy-or 16a,17a-epoxy-20-ketopregnanes. In the case of the 17-hydroxy compounds, substituents at C-16 readily survive e.g., 16 -Br, 16jS-Cl, Iba-OAc). The 16,17-oxido-20-oximinopregnanes produce 16a-acetoxy-17-ketones. 

The 10l -acetoxy group can be red actively removed with zinc and acetic acid or chromous chloride to give I9-norsteroids in high yield. Thermal elimination (boiling tetralin) of acetic acid from the crude 10)5-acetoxy-A -3-ketone or treatment with methanolic alkali leads to aromatization of ring A. Estrone alkyl ethers are formed from 10)5-acetoxy-19-nor-A -androstene-3,17-dione by treatment with alcohols and perchloric acid. Similar aromatizations are observed with 5,10-oxido, 5,10-dihydroxy, 5,10-halohydrins or 5,10-dihalo-3-ketones. ... 

The first sub-class of the oxido reductases is 1.1, and it comprises the dehydrogenases which act on primary or secondary alcohols or hemiacetals. They are mostly used for reduction of ketones and aldehydes. Two other categories are oxygenases and oxidases. The latter is not much used in biocatalysis. 

A one-carbon homologation of carbonyl compounds is an important and extensively used method for the preparation of desired carbonyl compounds . One-carbon ring-expansion or one-carbon homologation of ketones or aldehydes via a S-oxido car-benoid is a representative example of the homologation, but few methods have been reported . 

Satoh and coworkers further investigated this reaction and found that, in some cases, magnesium /3-oxido carbenoids gave better results. Trapping of the enolate intermediates with several electrophiles was successfully carried out and a new method for the synthesis of one-carbon expanded cyclic a,a-disubstituted ketones from lower cyclic ketones was realized. An example using 1,4-cyclohexanedione mono ethylene ketal (195) as a representative cyclic ketone is shown in Table 15. ... 

Application of the method described above to unsymmetrical cyclic ketones such as 2-substituted cyclohexanones gave 2,7-disubstituted and 2,2,7-trisubstituted cycloheptanones (Scheme 8). Treatment of a-sulfinyl lithium carbanion of 1-chloroethyl p-tolyl sulfoxide with 2-substituted cyclohexanones (210a and 210b) afforded adducts as a mixture of two diastereomers. The main adducts were first treated with f-BuMgCl followed by i-PrMgCl (4 equiv) at 0°C to room temperature to give the magnesium /3-oxido carbenoid 211. The... 

The /3-oxido carbenoid rearrangement then took place to give one-carbon expanded magnesium enolate having a chlorine atom (217), which was treated with water to afford a-chloroketone (218) in moderate yield. Unfortunately, this method could not be applied to larger cycloalkanones and acyclic ketones. Application of this method to aldehydes gave chloromethyl aryl ketones and chloromethyl alkyl ketones in moderate yields. ... 

Chemical systems of relevance to the molybdenum and tungsten enzymes include synthetic pterins, a-phosphorylated ketones (as precursor models), and a variety of molybdenum and tungsten oxido, sulfido, and 1,2-enedithiolate complexes. These compounds have been used to (1) confirm the identity of MPT derivatives (2) define steps in MPT biosynthesis (3) calibrate spectroscopic observations (4) give precise geometries and reactivities that can be used as input for theoretical studies and (5) provide options for mechanistic consideration. 

Prepared by Robinson condensation of 2,3,5-trimethoxytetrahydro-furan 88, 49) (available from furan), the ketone XXIX gave with subsequent reduction the 6-methoxytropan-3a-ol (XXXII) (see Section III,B) which, in turn, was demethylated by aqueous hydrogen bromide (90%) to (+ )-tropan-3a,6j8-diol (XXXI). As a condensing agent, p-toluenesulfonic anhydride gave good yields of 3a,6a-oxido-tropane (XLVI). 

Diverse soluble enzymes, called aldo-keto reductases. cany out bioreduction of aldehydes and ketones. They are found in the liver and other tissues (e.g.. kidney). As a general class, these soluble en7.ynie.s have similar physi-ochemical properties and broad substrate specificities and require NADW as a cofactor. Oxidoreductase enzymes that catty out both oxidation and reduction reactions also can reduce aldehydes and ketones. " For example. Ihe important liver alcohol dehydrogenase is an NAD -dependent oxido-icductase that oxidizes ethanol and other aliphatic alcohols to aldehydes and ketones. In the presence of NADH or... 

An interesting application of the method by Jeger s group d is to 8a,20-oxido-manool (5). On oxidation in aqueous dioxane the initially formed o-hydroxyaldehyde (6) suffered reverse aldolization to give the methyl ketone (7) and formaldehyde. 

Methyl 4 6-0-ethylidene-2 3-0-oxido-diethylidene- 8-D-glucopyranoside, 4 Methyl ethyl ketone, 450 Methyl irons,irons-farnesate, 227... 

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