Carbonyl compounds Aldehydes Ketones

In order to characterize them and more readily separate them from interfering accompanying substances carbonyl compounds (aldehydes, ketones) can be converted to hydrazones at the start. The reagent mainly employed is 2,4-dinitro-phenylhydrazine in acidic solution [70], This yields osazones with aldoses and ketoses. Some examples are listed in Table 15. 

Alcohols are among the most versatile of all organic compounds. They occur widely in nature, are important industrial 7, and have an unusually rich chemistry. The most widely used methods of alcohol synthesis start with carbonyl compounds. Aldehydes, ketones, esters, and carboxylic acids are reduced by reaction with LiAlH4. Aldehydes, esters, and carboxylic acids yield primary alcohols (RCH2OH) on reduction ketones yield secondary alcohols (R2CHOH). 

Table 6 Reaction of carbonyl compounds (aldehydes, ketones) with C-H acidic compounds, a selection.

Supplement 1941 1-161 Derivatives. Methyl alcohol, 273. Ethyl alcohol, 292. Ethyl ether, 314. Glycerol, 502. Carbonyl Compounds Aldehydes, Ketones, Ketencs and Derivatives. Formaldehyde, 558. Acetaldehyde, 635. Acetone, 635. Ketene, 724. Hydroxy-Carbonyl Compounds Aldehyde-Alcohols, Ketone-Alcohols, Monosaccharides and Derivatives. Glycolaldehyde, 817. Aldol, 824. Pentoses, 858. Hexoses, 878. 

Only scare data is available in the literature on the application of rhenium containing mono- or bimetallic catalysts in the hydrogenolysis of esters to alcohols. Decades ago Broadbent and co-workers studied the hydrogenation of organic carbonyl compounds (aldehydes, ketones, esters, anhydrides, acids,... 

The initial carbon-carbon bond formation (— 84) is often reversible, and a subsequent step—such as dehydration—may be necessary to displace the equilibrium. The many different (often named) reactions really differ from each other only in the nature of the particular carbonyl compound (aldehyde, ketone, ester, etc.), and in the type of carbanion, employed. 

During the first month of this experiment, it was realized that this reaction is extremely variable. Thus, diverse amines (ammonia, primary and secondary amines, hydrazine derivatives, hydroxylamines) 13, carbonyl compounds (aldehydes, ketones) 14, acid components 15 or their anions (H2O, Na2S203, H2Se, R2NH, RHN-CN, HN3, HNCO, HNCS, RCO2H, RCOSH, ROCO2H, etc.), and the isocyanides could form the a-adducts 16 that rearrange into their products 17 (Scheme 1.5). 

E)- or (Z)-y-alkoxyallylstannanes, Bu3SnCH2CH=CHOR, undergo a light-promoted reaction with various classes of carbonyl compounds (aldehydes, ketones, O -diketones) to give homoallylic alcohols with retention of double-bond geometry. 

Organic carbonyl compounds—aldehydes, ketones, amides, and acyl halides—in which the carbonyl group is not part of a cyclic structure have interesting conformational properties that may differ widely according to the molecular system bearing these substituents. 

On the basis of differences in electronegativity, tlie C - Si bond possesses 12% ionic character. Silicon is the positive end and carbon is the negative end of the dipole. Trimethyl(trifliioro-methyl)silane is thus a reagent for introducing the trifluoromethyl group into carbonyl compounds (aldehydes, ketones, enoncs). ... 

Chapters 20 through 24 of this text discuss carbonyl compounds—aldehydes, ketones, acid halides, esters, amides, and carboxylic acids. The carbonyl group is perhaps the most important Functional group in organic chemistry, because its electron-deficient carbon and easily broken 7t bond make it susceptible to a wide variety of useful reactions. 

The Schiff bases (they may be also considered as specific hydrazones) play a great role in the chemistry of N-aminoazoles. In most cases, these compounds are obtained by cyclization of a suitable acyclic compound or by interaction of an N-aminoazole with carbonyl compounds aldehydes, ketones, or their acetals. Usually the reaction is carried out on heating components in acetic acid or in alcohol in the presence of catalytic amounts of a mineral acid. The use of j3-dicarbonyl compounds requires more drastic conditions. Thus, 1-aminobenzimidazoles (83KGS386) or 7-amino-theophiline (87KGS155I) reacts with acetylacetone at I75°C in the presence of anhydrous zinc chloride, yielding hydrazones of type 283. 

The predominant conformation of a,P-unsaturated carbonyl compounds (aldehydes, ketones, esters) can vary when Lewis adds are coordinated to the carbonyl group, ft has been experimentally shown that the s-trans conformer of acrolein is more stable than the s-ds conformer, in the absence of any Lewis add. The two conformers are of almost equal stability in the case of acrylic acid or methyl acrylate 83] (Figure L21). The barriers between these conformers are low (4-9 kcal mol ). Interconversion is rapid, and the Curtin-Hammett principle ( 1.3) can be applied. 

Lithium aluminium hydride is a more powerful reducing agent than sodium borohydride and reduces most of the commonly encountered organic functional groups (see Table 7.3). It reacts readily with water and other compounds that contain active hydrogen atoms and must be used under anhydrous conditions in a non-hydroxylic solvent diethyl ether and THF are commonly employed. Lithium aluminium hydride has found widespread use for the reduction of carbonyl compounds. Aldehydes, ketones, esters, carboxylic acids and lactones can all be reduced smoothly to the corresponding alcohols under mild conditions. Carboxylic amides are converted into amines or aldehydes, depending on the conditions and on the... 

Several examples of solvent-free reactions of hypervalent iodine reagents under microwave irradiation conditions have been reported [2, 68-72], A solvent-less oxidation of 1,4-dihydropyridines to the respective pyridines can be performed using [bis(trifluoroacetoxy)iodo]benzene at room temperature under microwave irradiation conditions [68], Carbonyl compounds (aldehydes, ketones and esters) can be converted into the respective a-[(2,4-dinitrobenzene)sulfonyl]oxy carbonyl compounds by the reaction of the neat carbonyl compounds with [hydroxy(2,4-dinitrobenzenesulfonyloxy)iodo]benzene (HDNIB) under microwave irradiation in less than 40 s [69], Likewise, a-halocarbonyl compounds 55 can be conveniently prepared by sequential treatment of carbonyl compounds 54 with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation (MWI) conditions (Scheme 6.21) [70],... 

Compounds that have hydroxyl groups on adjacent atoms undergo oxidative cleavage when they are treated with aqueous periodic acid (HIO4). The reaction breaks carbon—carbon bonds and produces carbonyl compounds (aldehydes, ketones, or acids). 

Tian et al. [188a] described the synthesis of very useful protected homoallylic amines by a four-component reaction catalyzed by the inexpensive and environmentally friendly FeSO HjO. The reaction between carbonyl compounds (aldehydes, ketones, ketals, acetals) 200, CbzCl, HMDS, and allyltrimethylsilane afforded the corresponding homoallylic amines 201 in 43-87% yields (Scheme 3.73, Eq. 1) under mild conditions. This methodology was also applied to the synthesis of A-protected primary and branched amines 202 by replacing the allyltrimethylsilane for EtjSiH [188b], which gave rise to the desired products in 40-95% yields (Scheme 3.73, Eq. 2). 

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