Nonconjugated dienes oxidation

As mentioned above nonconjugated dienes give stable complexes where the two double bonds can form a chelate complex. A common pathway in palladium-catalyzed oxidation of nonconjugated dienes is that, after a first nucleophilic addition to one of the double bonds, the second double bond inserts into the palladium-carbon bond. The new (cr-alkyl)palladium complex produced can then undergo a /(-elimination or an oxidative cleavage reaction (Scheme 2). An early example of this type of reaction, although not catalytic, was reported by Tsuji and Takahashi (equation 2)12. 

Compared with conjugated dienes, the electrochemistry of nonconjugated dienes is classified into two types, A and B11,12. In type A, the double bond of the diene behaves essentially the same as the double bond of a monoolefin in the anodic oxidation. A typical... 

Despite the fact that the electrochemical oxidation of most of the nonconjugated dienes generally does not give products which result from interaction of the double bonds with one another, the anodic oxidation l-acetoxy-l,6-heptadienes gives intramolecularly cyclized products, that is, the cyclohexenyl ketones (equation 15)13. The cyclization takes place through the electrophilic attack of the cation generated from enol ester moiety to the double bond. 

The ionic chain polymerization of unsaturated linkages is considered in this chapter, primarily the polymerization of the carbon-carbon double bond by cationic and anionic initiators (Secs. 5-2 and 5-3). The last part of the chapter considers the polymerization of other unsaturated linkages. Polymerizations initiated by coordination and metal oxide initiators are usually also ionic in nature. These are called coordination polymerizations and are considered separately in Chap. 8. Ionic polymerizations of cyclic monomers is discussed in Chap. 7. The polymerization of conjugated dienes is considered in Chap. 8. Cyclopolymerization of nonconjugated dienes is discussed in Chap. 6. 

NaOH-HiOz) or to carboxylic acids (with w-chloroperbenzoic acid).-190 Double bonds can be hydroborated in the presence of triple bonds if the reagent is 9-BBN.191 On the other hand, dimesitylborane selectively hydroborates triple bonds in the presence of double bonds.192 Furthermore, it is often possible to hydroborate selectively one particular double bond of a nonconjugated diene.191 When the reagent is catecholborane, hydroboration is catalyzed by rhodium complexes, such as Wilkinson s catalyst.194 Enantioselective hydro-boration-oxidation has been achieved by the use of optically active rhodium complexes.195... 

Compared with simple aliphatic alkenes and coiyugated dienes, the behavior of noncoiyugated dienes in anodit oxidation is unique. The possible reaction padiway of the oxidation of nonconjugated dienes... 

The ubiquitous and reversible formation of radical cations in photoelectrochemical transformations allows pericyclic reactions to take place upon photocatalytic activation since the barriers for pericyclic reactions are often lower in the singly oxidized product than in the neutral precursor. For example, ring openings on irradiated CdS suspensions are known in strained saturated hydrocarbons [176], and formal [2 -I- 2] cycloadditions have been described for phenyl vinyl ether [ 177] and A-vinyl carbazole [178]. The cyclization of nonconjugated dienes, such as norbomadiene, have also been reported [179]. A recent example involves a 1,3-sigmatropic shift [180]. 

A number of reviews dealing with the palladium-catalyzed oxidation of unsaturated hydrocarbons have been written The present review will focus on the palladium-catalyzed oxidation of dienes including both conjugated and nonconjugated dienes. Since this topic has been thoroughly reviewed up to ca l979 in the book by Henryk the present review will mainly cover the time period 1979-95. During this time several reviews have been written which partly cover the present topic. 

The anodic oxidation of nonconjugated dienes has been classified into two categories ... 

Another type of oxycarborative addition is achieved when the organopalladium intermediate is trapped via alkene insertion. Thus, 1,5-hexadiene with acetic acid gives l-acetoxy-3-methylenecyclopentane (3) if mediated by palladium(ll) acetate10. This reaction is obviously restricted to 1,5-dienes, since other nonconjugated dienes and even some substituted 1,5-dienes lead to linear oxidation products. 

The case for coordinative unsaturation on polymers is rather weak and comes principally from the enhanced rates of hydrogenation observed for polymeric catalysts. Kaneda etal supported PdCb on a linear phosphin-ated polystyrene, and the hydrogenation of nonconjugated dienes was examined. " The supported catalyst was active even under conditions where PdCl2(PPh3)2 was inert. ESCA studies established a 2+ oxidation state for the metal. The increase in hydrogenation activity was considered to possibly have its origin in unsaturation at palladium. 

The copolymerization of propylene oxide with nonconjugated dienes... 

Ethylene oxide polysulfide Epoxy resin (ASTM, DIN, ISO, lUPAC) Copolymer from ethylene and propylene (ISO) see also AP, APR, EPM, EPR Easy processing channel black Elastomeric terpolymer from ethylene, propylene, and a nonconjugated diene (ASTM) see also APT, EPDM, EPT, EPTR... 

Nonconjugated perfluorocyclohepta-l,4-diene is oxidized to the corresponding diepoxide by sodium hypobromite [17] (equation 36), whereas the conjugated- 1,3-diene gives a mixture of 1,2-monoepoxide and bridged 2,3 1,4-diepox-ide [IT] (equation 36). 

Asatone (110 Scheme 25), a neolignan, was quickly assembled by capitalizing upon the ability of a nucleophilic solvent to intercept the intermediate cation formed upon the electrooxidation of (108) in this instance the conjugated 1,3-diene (109) was produced. This result contrasts with the oxidation of 4,5-dimethoxyphenol (101) (Scheme 23) wherein the nonconjugated 1,4-diene (102) was generated. Diene (109) served admirably as both the diene and the dienophile in an intermolecular Diels-Alder reaction leading to asatone (110) [51]. 

Epoxidation of various acyclic and cyclic perfluorinated dienes is accomplished with an aqueous hypohalogenitc and acetonitrile as a cosolvent. The reactivity of a C = C bond toward this reagent is enhanced by the presence of the trifluoromethyl group. This activating effect is nicely illustrated by perfluoro(l-methylcyclohexa-l,4-diene), which reacts smoothly with sodium hypochlorite to give a diepoxide 11 in 58% yield,73 while the oxidation system failed for perfluorocyclohexadienes. Nonconjugated perfluorocyclohepta-1,4-diene (12) is oxidized to the corresponding diepoxide 13 by sodium hypobromite.74... 

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