Additions ketones

The method has been applied to the reduction of cholestanone. Red uction of this ketone with the mixed reagent and no additional ketone gave 17% of the a-epimer under the equilibration conditions only 3p-ol and unreduced ketone are obtained. Reduction of coprostanone with the mixed reagent gives 94% of the 3a-ol. ... 

Tn general. Nelson and Schut s procedure is recommended for expansion of an unsymmetrically substituted cyclohexanone (for example, the A ring of a steroid 3-ketone). The yield is satisfactory in most instances and the precursors are readily available. However, the relative proportions of the two possible ketones may change as substituents are varied. The procedure is applicable to systems with additional ketones protected as ketals, double bonds, ethers and hydroxyl groups. 

There are a series of communications about the formation of dihydroazines by direct reaction of urea-like compounds with synthetic precursors of unsaturated carbonyls—ketones, containing an activated methyl or methylene group. The reaction products formed in this case are usually identical to the heterocycles obtained in reactions of the same binuclephiles with a,(3-unsatu-rated ketones. For example, interaction of 2 equiv of acetophenone 103 with urea under acidic catalysis yielded 6-methyl-4,6-diphenyl-2-oxi- 1,6-dihydro-pyrimidine 106 and two products of the self-condensation of acetophenone— dipnone 104 and 1,3,5-triphenylbenzene 105 [100] (Scheme 3.32). When urea was absent from the reaction mixture or substituted with 1,3-dimethylurea, the only isolated product was dipnon 104. In addition, ketone 104 and urea in a multicomponent reaction form the same pyrimidine derivative 106. All these facts suggest mechanism for the heterocyclization shown in Scheme 3.32. 

In this Diels-Alder reaction with inverse electron demand the overlap of the LUMO of the 1-oxa-l,3-butadiene with the HOMO of the dienophile is dominant. Since the electron-withdrawing group of the oxabutadiene at the 3-position lowers its LUMO dramatically, both the cycloaddition and the condensation usually take place at room temperature. The reaction can be performed as a two-, three- or four-component transformation. There is actually no restriction on the aldehydes thus, aromatic, hetero-aromatic, saturated aliphatic and unsaturated aliphatic aldehydes may be used. In addition, ketones such as a-oxocarbocylic esters can also be employed. As 1,3-dicarbonyl compounds cyclic substances such as Meldrum s acid, barbituric acid and derivates, coumarines, any type of cycloalkane-1,3-dione and / -ketoesters, as well as their phosphorus, nitrogen or sulfur analogues and acyclic... 

In addition, ketones and aldehydes also undergo cleavage of tJk-between the carbonyl group and the neighboring carbon. Alpha cleav yields a neutral radical and an oxygen-coniaintng cahon. 

The Luche reduction is an excellent method for the 1,2-reduction of a,p-unsaturated ketones. In addition, ketones are reduced selectively in the presence of aldehydes. 

The yields of the pyrimidines 147 and the pyridines 151 are not high and vary greatly, depending on the structure of the starting materials. The latter can also determine the nature of the product. Thus, a mixture of 2,4-dimethyl-6-phenylpyrimidine, 2,4-dimethyl-4,6-diphenyl-4//-l,3-oxazine and 1-chloro-l-phenylethene was obtained by refluxing a 1 3 3 ratio of the acetophenone-benzonitrile-phosphorus oxychloride mixture, followed by treatment of the crude product with sodium carbonate solution .It has been shown that addition of an additional ketone molecule to the iminium intermediate is an alternative to the formation of the A -acylenamines and this route is catalyzed by aluminum chloride. Auricchio and coworkers believe also that the reaction of ketones with nitriles catalyzed with both protic and Lewis acids must be considered as a Ritter reaction (see, however, Section V.C). The cationic intermediate 152 thus formed can undergo either a proton shift giving enamide 153 or addition of another ketone molecule... 

The reaction between diaziridine and additional ketone produces azine, which is hydrolyzed to form hydrazine with the regeneration of ketone. There are two improvements over the Raschig process, namely, 1) use of ketone as a nitrogen carrier and 2) stabilizing the N-N bond of hydrazine. 

A Wadsworth-Emmons type reaction of diethyl t-butoxy(cyano)methyl-phosphonate (1) has been used for the homologation of aldehydes and ketones to acids, esters, and amides (Scheme 2). Clearly, the method is limited to compounds which are reasonably stable to both heat and Lewis acids. In addition, ketonic precursors must have at least three a-protons. Inside these limits, good yields are obtained (57—88%). 

Nitrocellulose lacquers can be formulated with a large number of ketone solvents. Acetone, a fast evaporating solvent, will tolerate large additions of cheaper aromatic diluents to the nitrocellulose lacquers. The low viscosity of acetone and the hydrocarbon additions affords low solution viscosities. Other ketones that are useful as nitrocellulose solvents and that have high aliphatic and aromatic dilution ratios include MEK and MIBK. Additional ketones that find use in nitrocellulose lacquers include methyl /i-amyl ketone, methyl isoamyl ketone, dipropyl ketone, diisobutyl ketone, and cyclohexanone. Selection of the ketone often will depend on the desired evaporation rate. 

The brain and blood cells depend on glucose as the main fuel. The liver, kidney cortex, and both cardiac and skeletal muscle obtain most of their energy from the oxidation of free fatty acids. In addition, ketone bodies can make a major contribution to the fuel of respiration in brain, renal cortex, and cardiac skeletal muscle. 

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