Alkenes, oxidative cleavage reagent

Methods of synthesis for carboxylic acids include (1) oxidation of alkyl-benzenes, (2) oxidative cleavage of alkenes, (3) oxidation of primary alcohols or aldehydes, (4) hydrolysis of nitriles, and (5) reaction of Grignard reagents with CO2 (carboxylation). General reactions of carboxylic acids include (1) loss of the acidic proton, (2) nucleophilic acyl substitution at the carbonyl group, (3) substitution on the a carbon, and (4) reduction. 

The oxidative cleavage of C=C bond is a common type of reaction encountered in organic synthesis and has played a historical role in the structural elucidation of organic compounds. There are two main conventional methods to oxidatively cleave a C=C bond (1) via ozonol-ysis and (2) via oxidation with high-valent transition-metal oxidizing reagents. A more recent method developed is via the osmium oxide catalyzed periodate oxidative cleavage of alkenes. All these methods can occur under aqueous conditions. 

This is one of the most important applications for RuO. Oxidative cleavage of alkenes and alkynes by a variety of reagents has been reviewed [30, 35, 50, 60, 68-71]. The gentler cleavage reactions of alkenes to aldehydes or ketones are considered first (Table 3.3), then the commoner cases of cleavage to carboxylic acids (Table 3.6). 

As with alkene cleavage the main reagent for alkyne oxidations is RuO. Oxidative cleavage of alkynes by a variety of reagents has been reviewed [4, 6, 12, 14, 15], The first oxidation of alkynes was noted by Pappo and Becker in 1956 they showed that l,2-fc/x(l-acetoxycyclohexyl)ethyne (2) (Fig. 1.5) gave the diketone. Minimal experimental details were given [195],... 

Oxidative cleavage of alkenes to aldehydes, ketones or carboxylic acids is an important transformation usually carried out by ozonolysis or oxidation with stoichiometric oxidants, i.e. OSO4, MnO 1 etc.199. The serious drawbacks of most of these reagents,... 

From oxidative cleavage of 1,2-diols and 1,2-amino alcohols Dibutyltin oxide, 95 By reaction of alkyl halides with sulfur-stabilized carbanions Methylthiomethyl p-tolyl sulfone, 192 From reduction of carboxylic acids Vilsmeier reagent, 341 From terminal alkenes by addition reactions... 

Among the other reagents listed, activated Mn02 is specific for the oxidation of allylic and ben/ylie alcohols.22 KM11O4 is used for the oxidation of alkenes to diols.23 Ceriv(lV) ammonium nitrate (CAN) accomplishes oxidative cleavage of the PMB protecting group. 

Alkenes can he dihydroxylated cw-selectively by reaction with a stoichiometric amount of N-methylmorpholine-jV-oxide (NMO), a catalytic amount of a suitable Os(VIII) reagent, and some water. From a preparative point of view, this reaction is closely related to oxidative cleavages, and for this reason it is introduced now (Figure 17.19). 

The reagents that effect the oxidative cleavage of alkene C=C double bonds (Figures 17.26-17.28) in principle also are suitable for the cleavage of aromatic C=C double bonds (Figures 17.29-17.31). The mechanism is unchanged. 

Show how to synthesize carboxylic acids from oxidation of alcohols and aldehydes. Problems 20-36, 39, and 44 carboxylation of Grignard reagents, oxidative cleavage of alkenes and alkynes, hydrolysis of nitriles, and oxidation of alkylbenzenes. 

Ozone is a reagent for the oxidative cleavage of C=C double bonds. The products have carbonyl groups at the ends of the old alkene. The mechanism is described in Chapter 35. 

Aldehydes and ketones are among the most important of all compounds, both in biochemistry and in the chemical industry. Aldehydes arc normally prepared in the laboratory by oxidative cleavage of alkenes, by oxidation of primary alcohols, or by partial reduction of esters. Ketones are similarly prepared by oxidative cleavage of alkenes, by oxidation of secondary alcohols, or by addition of diorganocopper reagents to acid chlorides. 

The (3-methyl homoallylic alcohol moiety of both anti- and 5yn-configurations is a characteristic structural element of a number of macrolides and polyether antibiotics. Reactions of crotylmetal (2-butenylmetal) reagents with carbonyl substrates provide access to acyclic stereo- and enantioselective syntheses of p-methyl homoallylic alcohols. The alkene moiety of these alcohols can be further elaborated into aldehydes by oxidative cleavage of the double bond, leading to aldol-type products. 

Henry, J. R., Weinreb, S. M. A convenient, mild method for oxidative cleavage of alkenes with Jones reagent/osmium tetraoxide. J. Org. Chem. 1993, 58, 4745. 

Oxidative cleavage of alkenes. Although this reagent (1) can cleave terminal and internal alkenes, the yields can be low. However, much higher yields can be obtained if the substrate bears an alkoxy or an ester group even remote from the double bond (equations I and 11). 

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