Ketones compounds

The condensation of aldehydes and ketones with succinic esters in the presence of sodium ethoxide is known as the Stobbe condensation. The reaction with sodium ethoxide is comparatively slow and a httlo reduction of the ketonic compound to the carbinol usually occurs a shorter reaction time and a better yield is generally obtained with the more powerful condensing agent potassium ieri.-butoxide or with sodium hydride. Thus benzophenone condenses with diethyl succinate in the presence of potassium [Pg.919]

The yield can be raised to 28% if the Hofmann elimination is conducted in the presence of a water-soluble copper or iron compound (19). Further improvements up to 50% were reported when the elimination was carried out in the presence of ketone compounds (20). Further beneficial effects have been found with certain cosolvents, with reported yields of greater than 70% (8). 

New synthetic routes for the preparation of homologously pure dichloro DPX and tetrachloro DPX have been reported through the 1,6-Hofmaim elimination of chlotinated j -methy1ben2y1trimethy1 ammonium hydroxide. In the case of dichloro DPX, yields of 30% were reported (21). In the presence of ketone compounds, yields were iacreased to 50% (20). 

Diazomethane reacts with ketonic compounds according to the reactions to give epoxides and homologated ketones. If the ketone employed is cyclic, only a single... 

There are a number of nitro-compounds known under the name of artificial musk, all of which may conveniently be grouped together here. The natural odorous constituents of musk appear to be, in the main, ketonic compounds free from nitrogen, so that the term artificial musk must be understood to mean artificially prepared bodies, having musklike odours, but not having any direct chemical relationship with natural musk perfume. 

TSie processes depending on the use of sodium bisulphite or sulphite, and in which the aldehyde or ketone compounds dissolve in the solution of the reagent, are known as absorption processes, and are those most commonly employed for oils containing a high proportion of aldehydes and ketones, the use of sodium bisulphite being probably still the method most usually adopted for aldehydes, though the use of neutral sodium sulphite is the official process in the British Pharmacopoeia of 1914, and is also that most suitable for the estimation of ketones. 

The aldehyde and ketone compounds formed with the sodium sulphite are readily soluble in water, and H. E. Burgess makes use of this fact... 

Purely aromatic ketones generally do not give satisfactory results pinacols and resinous products often predominate. The reduction of ketonic compounds of high molecular weight and very slight solubility is facilitated by the addition of a solvent, such as ethanol, acetic acid or dioxan, which is miscible with aqueous hydrochloric acid. With some carbonyl compounds, notably keto acids, poor yields are obtained even in the presence of ethanol, etc., and the difficulty has been ascribed to the formation of insoluble polymolecular reduction products, which coat the surface of the zinc. The adffition of a hydrocarbon solvent, such as toluene, is beneficial because it keeps most of the material out of contact with the zinc and the reduction occurs in the aqueous layer at such high dilution that polymolecular reactions are largdy inhibited (see Section IV,143). 

Hg. Allylmercury bromide and diallylmercury are both stable in water. They can allylate aldehydes in aqueous media but, in the case of allylmercury bromide, activation with tetrahexylammonium bromide was necessary.186 The allylation reaction is chemoselective towards aldehyde on the contrary, ketone compounds are unaffected. 

Zinc hydroxide and alkoxide species are particularly relevant to catalytic processes, often forming the active species. The cooperative effects of more than one zinc ion and bridged hydroxides are exploited in some enzymatic systems. Zinc alkyl phosphate and carboxylate materials have been important in the formation of framework compounds, often containing large amounts of free space for the inclusion of guest molecules. Aldehyde and ketone compounds are of low stability due to the poor donor capabilities of the ligands however, a number of examples have recently been characterized. 

Experiments attempting the interaction of D-glucose with ethyl O-pro-pionylacetoacetate have proved fruitless. A positive result for this compound, in which the enolic structure has been fixed by substitution on the oxygen, would have been favorable to theories based on involvement of the enolic form of the ketonic compound. 

Hydroboration and oxidation of 160 yields an alcohol that is subsequently oxidized with PDC to give ketone compound 161. Enolization and triflation converts this compound to enol triflate 162, which can be further converted to x,/i-unsaturated ester 163 upon palladium-mediated carbonylation methox-ylation. The desired alcohol 164 can then be readily prepared from 163 via DIBAL reduction. Scheme 7 50 shows these conversions. 

An extension of the strategy described for the reaction with aldehydes (Section 5.4.2) to imine derivatives might be expected to yield a-amino ketone compounds (Scheme 5.14), which are the constituents of a variety of biologically important molecules. 

However, these reactions jure associated with terminal rather than bridging carbonyl groups. In metal "ketonic compounds, the center for attack is normally the metal. This may be rationalized in terms of additional delocalization of the positive charge from the carbon to the metal center and implies a "carbyne contribution to the carbonyl bridge, of the form discussed above for the methylated products, again emphasizing the possibility that in systems of this type reaction may occur at either the metal or ligand center... 

For further contributions on the dia-stereoselectivity in electropinacolizations, see Ref. [286-295]. Reduction in DMF at a Fig cathode can lead to improved yield and selectivity upon addition of catalytic amounts of tetraalkylammonium salts to the electrolyte. On the basis of preparative scale electrolyses and cyclic voltammetry for that behavior, a mechanism is proposed that involves an initial reduction of the tetraalkylammonium cation with the participation of the electrode material to form a catalyst that favors le reduction routes [296, 297]. Stoichiometric amounts of ytterbium(II), generated by reduction of Yb(III), support the stereospecific coupling of 1,3-dibenzoylpropane to cis-cyclopentane-l,2-diol. However, Yb(III) remains bounded to the pinacol and cannot be released to act as a catalyst. This leads to a loss of stereoselectivity in the course of the reaction [298]. Also, with the addition of a Ce( IV)-complex the stereochemical course of the reduction can be altered [299]. In a weakly acidic solution, the meso/rac ratio in the EHD (electrohy-drodimerization) of acetophenone could be influenced by ultrasonication [300]. Besides phenyl ketone compounds, examples with other aromatic groups have also been published [294, 295, 301, 302]. 

Elba reaction org chem The formation of anthracene derivatives by dehydration and cycllzation of diaryl ketone compounds which have a methyl group or methylene group heating to an elevated temperature is usually required. elbs re.ak shan ( ELDOR See electron electron double resonance. ( el,dor or e el de o ar ( electrical calorimeter analy chem Device to measure heat evolved (from fusion or vaporization, for example) measured quantities of heat are added electrically to the sample, and the temperature rise is noted. a lek tra kal kal a rlm ad ar)... 

The a-halo ketone compound has also been prepared in situ. Dimedone reacts with 2-mercaptotriazoles in the presence of bromine to give 150 (91H231). 

The first application of NMR diffusion measurements to determine the aggregation state of a transition metal catalyst concerned the chiral, tetranuclear Cu(i) catalysts 130-132, used in the conjugate addition reactions of anions to a,p-unsatu-rated cyclic ketones. Compounds 130-132 react wdth isonitriles to form 133-135, and do not degrade to lower molecular weight species (see Eq. (20)) [109]. 

The reaction mixtures contained 5 and 0.5 mg of cells, respectively, in a total volume of 1 mL. To half the batches 1 mM NADP was added to check whether the amount of intracellular cofactor was sufficient to perform efficient reactions. Starting from 10 mM acetophenone, this ketone compound was completely reduced after a short reaction time by E. coli BL21(DE3)/pAW-3 and by E. coli BL21(DE3)/pAW-4 cells (0.5 mg of each) (Eig. 2.2.4.7). 

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