Formation of Aldehydes and Ketones

Aldehydes are prepared by carbonylation in the presence of hydride sources. Formation of aldehydes can be understood by transmetallation of acylpalladium 56 with a hydride to give acylpalladium hydride 57, followed by reductive elimination. Metal hydrides and hydrogen are used for aldehyde synthesis. Hydrosilane is one of the hydrides. Reaction of /I-naphthyl triflate (58) with EtsSiH using DPPF as a ligand under mild conditions afforded the aldehyde 59 [28]. Carbonylation of the alkenyl triflate 60 in the presence of tin hydride and LiCl afforded the aldehyde 61 in 95 % yield [29]. 

Ketones are prepared by transmetallation of acylpalladium 62 with organo-metallic reagents. Phenyl triflate was converted to acetophenone (64) by carbonylation in the presence of Me4Sn [30]. 

In the total synthesis of strychnine, Overman prepared the alkenyl aryl ketone 67 in 80 % yield by the carbonylation of the aryl iodide 65 with the alkenylstannane 66 using AsPhs as a ligand [31]. 

Chloroanisole, activated by coordination of electron-attracting Cr carbonyl 68, reacted with CO and dimethylindium 69 to afford the methyl ketone 70 under mild conditions [32]. Also Bus In was used for the preparation of butyl phenyl ketone (71) [33]. 

Ketones are also prepared by carbonylation in the presence of alkenes. Carbony-lation of 4-iodoanisole in the presence of dihydrofuran (72) provided the ketone 73 via insertion of the double bond in dihyrofuran to acylpalladium, followed by f-H elimination [34], 

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The most popular reagent for the formation of aldehyde and ketone derivatives is 2,4-dinitrophenylhydrazine which forms hydrazones containing strong chromophores. 

TABLE 9. Representative examples of the formation of aldehydes and ketones /... 

Table 3.41. Formation of aldehydes and ketones by cleavage of carboxylic acid derivatives, alkenes, diols, and ethers.

NEF REACTION. Formation of aldehydes and ketones from primary and secondary nitroparaffins, respectively, by treatment of their salts with snlfnric acid. 

Formation of aldehydes and ketones. The oxidation of alcohols can lead to the formation of aldehydes and ketones. Aldehydes are formed from primary alcohols, while ketones are formed from secondary alcohols. 

Polyethylene. The action of ozone on polyethylene was studied in the temperature range from 25° to 109° C. The reaction was followed qualitatively and quantitatively by infrared spectra. The products appeared to be of the same nature as those of O2 oxidations of polyethylene 2)—i.e., the formation of aldehydic and ketonic groups as indicated by the appearance of a strong absorption band in the region of 5.9 microns, and the existence of hydroxyl groups as shown by the 2.9-micron band. Polyethylene is readily oxidized in the presence of ozone, as even short period ozonizations carried out at temperatures as low as 25° C. yielded considerable concentrations of carbonyl and hydroxyl groups. Pure O2 oxidations did not yield comparable results until the reaction temperature was raised approximately... 

Fuson, R. C. Formation of aldehydes and ketones from carboxylic acids and their derivatives, in The Chemistry of the Carbonyl Group (ed. 

Gorgues, A., Formation of aldehydes and ketones by reaction of formic acid with their acetals. Laboratory note. Bull. Soc. Chim. Fr., 529, 1974. 

Alkoxysulfonium salt 30, R=cyclohexyl, is isolable and has been fully characterized [73]. Decomposition of these salts in acetonitrile leads to alkenes, ethers, and AT-alkylacetamides. Notably absent from this list of decomposition products are aldehydes and ketones which are typically formed by the decomposition of alkoxysulfonium salts 31 derived from dimethylsulfoxide [74,75]. The lack of formation of aldehydes and ketones from 30 is consistent with the known mechanism [76-78], shown in Eq. (21), for formation of these compounds from 31 ... 

The number of NO molecules converted to N02 per hydrocarbon molecule is given for two stages of the oxidation from the initial stage leading only to the formation of aldehydes and ketones, and for the further oxidation of the carbonyl compounds. 

Many methods have been developed for the oxidation of primary and secondary alcohols. Oxidation of secondary alcohols normally gives rise to ketone products, whereas primary alcohols form aldehydes or carboxylic acids, depending on the reagent and conditions. Selective oxidation reactions have been developed that give these different types of products, even in the presence of other sensitive functionality. This section will describe, in turn, the different reagents used for the formation of aldehydes and ketones, before discussing the formation of carboxylic acids. 

Surface oxidation reactions have been carried out on a number of polymers, particularly polyethylene. Surface oxidation techniques include the use of corona discharge, ozone, hydrogen peroxide, nitrous acid, alkaline hypochloride, UV irradiation, oxidizing flame, and chromic acid The reactions lead initially to the formation of hydroperoxides, which catalyze the formation of aldehydes and ketones and finally, acids and esters. Surface oxidation treatment has been used to increase the printabdity of polyethylene and poly(ethylene terephthalate) and to improve the adhesion of polyethylene and polypropylene to polar polymers and that of polytetrafluoroethylene to pressure-sensitive tapes. Surface-oxidized polyethylene, when coated with a thin film of vinylidene chloride, acrylonitrile, and acryhc acid terpolymers becomes impermeable to oxygen and more resistant to grease, oil, abrasion, and high temperatures. The greasy feel of polyethylene has also been removed by surface oxidation. 

In spite of the fact that the peroxide compounds formed during photodestruction, in the opinion of certain researchers [86], are more stable than the corresponding formation of aldehydes and ketones. According to the opinion expressed in [82], aldehydes are formed in the decomposition of secondary hydroperoxides, ketones in the decomposition of tertiary hydroperoxides. In the presence of oxygen, aldehydes are oxidized to acids under the action of light. 

The mechanism of acid-catalyzed esterification involves two stages. The first is formation of a tetrahedral intermediate by nucleophilic addition of the alcohol to the carbonyl group and is analogous to acid-catalyzed acetal and ketal formation of aldehydes and ketones. The second is dehydration of the tetrahedral intermediate. 

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