From ketones and aldehydes

Carbonylation of enol triflates derived from ketones and aldehydes affords Q,/)-unsaturated esters[332]. Steroidal esters are produced via their aryl and enol triflates[328]. The enol triflate in 477 is more reactive than the aryl tritlate and the carbonylation proceeds stepwise. First, carbonylation of the enol triflate affords the amide 478 and then the ester 479 is obtained in DMSO using dppp[333]. 

Ailyl enol carbonates derived from ketones and aldehydes undergo Pd-cat-alyzed decarboxylation-elimination, and are used for the preparation of a, /3-unsaturated ketones and aldehydes. The reaction is regiospecific. The regio-isomenc enol carbonates 724 and 726, prepared from 723, are converted into two isomeric enones, 725 and 727. selectively. The saturated aldehyde 728 can be converted into the a,/3-unsaturated aldehyde 730 via the enol carbonate 729[459]. 

Pinacol formation from ketones and aldehydes by cathodic reduction has been enhanced in the presence of Cr(II) complexes. Electrolysis of a mixture of ben-zophenone (364) and chromium chloride hexahydrate in a DMF-NaCl04 system... 

This process presents a typical procedure applicable to preparation of cyanohydrins from ketones and aldehydes of low reactivity. l-Cyano-6-methoxy-3,4-dihydronaphthalene is useful as an intermediate for synthesis of polycyclic compounds. 

Ketomethylene structures react with 6-amino-5-nitrosopyrimidines (49MI21600), providing a general route to 6- and 7-substituted pteridines from ketones and aldehydes (Scheme 33) (54JCS2881, 56JCS213). 

Triflates derived from phenols are carbonylated to form aromatic esters by using Pd-Ph3P. The carbonylation of triflates is 500 times faster if DPPP (XLIV) is used [219]. This reaction is a good preparative method of benzoates from phenols and naphthoates from naphthols [220]. Carbonylation of enol triflates derived from ketones and aldehydes affords a,/Cunsaturated esters. The enol triflate in 451 is more reactive than the aryl triflate and the carbonylation proceeds stepwise chemoselectively. At... 

Dehydrogenases responsible for hydrogen transfer between substrates possess NAD+ (nicotinamide) as the coenzyme, owing to which chiral alcohols are formed from ketones and aldehydes. 

Sec. 19.10) from ketones and aldehydes by acid-catalyzed reaction with alcohols... 

Alkanes, RH (Sec. 7.7) (Sec. 10.7) (Sec. 10.8) (Sec. 19.9) from alkenes by catalytic hydrogenation from alkyl halides by protonolysis of Grignard reagents from alkyl halides by coupling with Gilman reagents from ketones and aldehydes by Wolff-Kishner reaction... 

Methods for the preparation of hydrazones and oximes differ little from those used for the synthesis of imines from ketones and aldehydes in that the appropriate nitrogen species and the ketone are mixed. However, the equilibrium for the majority of reactions of ketones and aldehydes with hydrazines and hy-droxylamine favor the product hydr nes and oximes and removal of the water formed by the condensation is not required. 8(> Acid catalysis is complicated by the basicity of the reagent and, for example, the maximum rate of oxime formation is at approximately pH 4. Complicating reactions can occur such as the 1 2 combination of hydrazine with two ketones or aldehydes to form azines but this is not a problem with the substituted hydrazines that are used for asymmetric induction. 

According to the studies performed by the Bundesanstalt fur Materi-alprufung, Germany (BAM), this compound may explode when dry, but in the presence of 20% water there is no longer any danger of explosion. It is widely used in analytical organic chemistry for the preparation of dinitrophenylhydrazon and its derivates from ketones and aldehydes. 

Hydrolytic cleavage of the C-O bond of bicyclic, tetracyclic, and steroidal enolates with HF-SbFs induces their isomerization to the corresponding ketones (Scheme 14.41) [104]. Rearrangement of dienones to aromatic compounds is also promoted by HF-SbFs (Scheme 14.42) [105]. Ring expansion of methyl penicilli-nates is achieved by SbCls to give thiazepine derivatives [106]. 1,3-Dithianes derived from ketones and aldehydes are deprotected with SbCls by means of a single-electron-transfer mechanism [107]. 

Formation of N,A -dialkylhydrazones from ketones and aldehydes is generally a facile reaction. In the case of most aldehydes, all that is required is stirring of the unsymmetrical A/,fV-dialkylhydrazine with the aldehyde in the presence of a drying agent. In some cases, these reactions can be carried out at room temperature. Ketones react similarly but can require more vigorous conditions. In the case of less-reactive carbonyl substrates, acid catalysts like p-toluenesulfonic acid or azeotropic distillation are commonly used to promote hydrazone formation. Formation of the aldehyde and ketone dimethylhydrazones and of the chiral hydrazone in equations (l)- 4) are examples of typical procedures. Monosubstituted hydrazones such as (6) are prepared in a similar manner (equation 5). These reactions often proceed in near-quantitative yield. 

The 1,2-addition of simple azaallyllithium reagents derived from ketone and aldehyde dimethylhydra-zones to aldehydes and ketones was also first described by Corey and Enders.Regioselective deprotonation of 2-pentanone dimethylhydrazone with Bu"Li followed by addition of an aldehyde or... 

Table 1 Reagents for Regeneration of Carbonyl Compounds from Ketone and Aldehyde Hydrazones...

Looking carefully at the current literature we have learned that the ketene dithioacetal chemistry, widely used for one-carbon homologation of carbonyl compounds, has never been utilized for the construction of ulosonic acids [129]. Besides, ketene dithioacetals, readily available from ketones and aldehydes via the reaction with the ylides generated from substituted dithioacetals in the Peterson, Wittig or Homer-Emmons olefmation, have never been synthesized from lactones. 

C.i. Epoxides. Epoxides are easily generated from alkenes (sec. 3.4) and also from ketones and aldehydes 8.8.B). They are one of the most useful of all oxygenated functional groups. Reduction of epoxides leads to alcohols. Lithium aluminum hydride delivers hydride to the less sterically... 

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