Aldehydes hydroperoxide oxidation

Physical and Chemical Properties. The (F)- and (Z)-isomers of cinnamaldehyde are both known. (F)-Cinnamaldehyde [14371-10-9] is generally produced commercially and its properties are given in Table 2. Cinnamaldehyde undergoes reactions that are typical of an a,P-unsaturated aromatic aldehyde. Slow oxidation to cinnamic acid is observed upon exposure to air. This process can be accelerated in the presence of transition-metal catalysts such as cobalt acetate (28). Under more vigorous conditions with either nitric or chromic acid, cleavage at the double bond occurs to afford benzoic acid. Epoxidation of cinnamaldehyde via a conjugate addition mechanism is observed upon treatment with a salt of /-butyl hydroperoxide (29). 

CHO - COOH. This hydroperoxide oxidizes aldehydes to carboxyjic acids in generally satisfactory yields. The oxidation is conducted in CH2Cl2Na2C03 or C lljOll-NaOH. The oxidant does not attack alcohols. The oxidation, as in epoxidations with 1, can be effected with H202 and a catalytic amount of 1. 

Oxidation. Oxidations with r-butyl hydroperoxide catalyzed with this Mo complex can be used to effect selective oxidations of secondary alcohols in the presence of primary ones in benzene at 60°. Primary alcohols are oxidized slowly to esters in methanol. Aldehydes are oxidized to carboxylic acids in benzene or to esters in methanol. 

It is possible to oxidize an alcohol in the presence of sulfur- or selenium-containing groups (equation 16) using r-butyl hydroperoxide and a diselenide as the oxidizing system (this also oxidizes secondary alcohols, see later).Selenium chemistry can also be used to oxidize benzylic and related primary alcohols to the aldehydes without oxidizing pyridyl (18 equation 17) or thiophenyl (19 equation 18) groups. ... 

Ketones do not react with most of the reagents used to oxidize aldehydes. However, both aldehydes and ketones can be oxidized by a peroxyacid. Aldehydes are oxidized to carboxylic acids and ketones are oxidized to esters. A peroxyacid (also called a per-carboxylic acid or an acyl hydroperoxide) contains one more oxygen than a carboxylic acid, and it is this oxygen that is inserted between the carbonyl carbon and the H of an aldehyde or the R of a ketone. The reaction is called a Baeyer-Villiger oxidation. 

HA catabolism/degradation results in the formation of different HA fragments. The parental biopolymer and the enzyme-mediated HA fragments, regardless of chain length, have both identical chemical structure whereas fragmented chains produced under oxidative stress contain e.g. aldehyde-, hydroperoxide-, and other chemical groups [17]. 

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. 

Reaction of 66 with Ipc2BOMe followed by BF3 Et20 provides the allylborane 15. Allylation of aldehydes with 15 and subsequent alkaline hydroperoxide oxidation yields syn P-methoxy homo-allylic alcohol 69 in very high de and ee (Scheme 25.8). 

In contrast to oxidation in water, it has been found that 1-alkenes are directly oxidized with molecular oxygen in anhydrous, aprotic solvents, when a catalyst system of PdCl2(MeCN)2 and CuCl is used together with HMPA. In the absence of HMPA, no reaction takes place(100]. In the oxidation of 1-decene, the Oj uptake correlates with the amount of 2-decanone formed, and up to 0.5 mol of O2 is consumed for the production of 1 mol of the ketone. This result shows that both O atoms of molecular oxygen are incorporated into the product, and a bimetallic Pd(II) hydroperoxide coupled with a Cu salt is involved in oxidation of this type, and that the well known redox catalysis of PdXi and CuX is not always operalive[10 ]. The oxidation under anhydrous conditions is unique in terms of the regioselective formation of aldehyde 59 from X-allyl-A -methylbenzamide (58), whereas the use of aqueous DME results in the predominant formation of the methyl ketone 60. Similar results are obtained with allylic acetates and allylic carbonates[102]. The complete reversal of the regioselectivity in PdCli-catalyzed oxidation of alkenes is remarkable. 

Oxidation begins with the breakdown of hydroperoxides and the formation of free radicals. These reactive peroxy radicals initiate a chain reaction that propagates the breakdown of hydroperoxides into aldehydes (qv), ketones (qv), alcohols, and hydrocarbons (qv). These breakdown products make an oxidized product organoleptically unacceptable. Antioxidants work by donating a hydrogen atom to the reactive peroxide radical, ending the chain reaction (17). 

Usually, organoboranes are sensitive to oxygen. Simple trialkylboranes are spontaneously flammable in contact with air. Nevertheless, under carefully controlled conditions the reaction of organoboranes with oxygen can be used for the preparation of alcohols or alkyl hydroperoxides (228,229). Aldehydes are produced by oxidation of primary alkylboranes with pyridinium chi orochrom ate (188). Chromic acid at pH < 3 transforms secondary alkyl and cycloalkylboranes into ketones pyridinium chi orochrom ate can also be used (230,231). A convenient procedure for the direct conversion of terminal alkenes into carboxyUc acids employs hydroboration with dibromoborane—dimethyl sulfide and oxidation of the intermediate alkyldibromoborane with chromium trioxide in 90% aqueous acetic acid (232,233). 

The simple hydroperoxide mechanism so far discussed is incomplete for representing reactions with significant products other than hydroperoxides. It can be adequate for oxidations of certain unsaturates, aldehydes, and alkylaromatics where the yield of the corresponding hydroperoxide can exceed 90%. 

Oxidation. Olefins in general can be oxidized by a variety of reagents ranging from oxygen itself to ozone (qv), hydroperoxides, nitric acid (qv), etc. In some sequences, oxidation is carried out to create a stable product such as 1,2-diols or glycols, aldehydes, ketones, or carboxyUc acids. In other... 

Aromatic aldehydes and cyclic perfluoroketones are oxidized to a-hydroxy hydroperoxides or bis(a-hydroxy) peroxides, aliphatic ketones are converted to esters, and ketenes are converted to a-lactones... 

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