Ethers, unsaturated oxidation

Poly(ethylene terephtlhalate) Phenol-formaldehyde Polyimide Polyisobutylene Poly(methyl methacrylate), acrylic Poly-4-methylpentene-1 Polyoxymethylene polyformaldehyde, acetal Polypropylene Polyphenylene ether Polyphenylene oxide Poly(phenylene sulphide) Poly(phenylene sulphone) Polystyrene Polysulfone Polytetrafluoroethylene Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) Poly(vinyl butyral) Poly(vinyl chloride) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl formal) Polyvinylcarbazole Styrene Acrylonitrile Styrene butadiene rubber Styrene-butadiene-styrene Urea-formaldehyde Unsaturated polyester... 

Cyclization of unsaturated enol silyl ethers.1 Oxidation of certain 8,8- and 8,p-unsaturated enol silyl ethers with either CAN or Cu(OTf)2 can result in radical cyclization. 

Oxidation ofS,6-dihydropyranes. These cyclic allylic ethers are oxidized by PCCr directly to a, 3-unsaturated 8-lactones. 

Reagents which effect epoxidation of the enol ether unsaturation effect a-hydroxylation comparable to the peracid approach. Thus a combination of molybdenum hexacarbonyl and r-butyl hydroperoxide converts the substrates to a-silyloxy derivatives. The peroxide generate in situ from benzonitrile, potassium carbonate and hydrogen peroxide can also perform the oxidation. Molybdenum-peroxy complexes, including MoOPH, could presumably also effect this transformation. Lastly, dimethyldioxirane has been used to epoxidize alkenes and it is likely that application of this useful, debris free, organic peroxide to these reactions will soon emerge. 

Various substrates such as allyl alcohols, a,y3-unsaturated carbonyl compounds, and enol ethers undergo oxidative cleavage to afford the corresponding carbonyl compounds (Eqs. 3.35-3.37) [69-71], cis-Dihydroxylation occurs selectively, when the... 

The required a-hydroxy ketones are accessible via a variety of synthetic methods, including the acyloin condensation (see Chapter 9), oxidation of ketone enolates, oxidation of enol ethers,and oxidation of a, 3-unsaturated ketones,as depicted below. 

Construction of the triene required for the Diels-Alder cycloaddition began with the chain extension of glycidaldehyde (8) to the a,p-unsaturated ester and hydrolysis to the diol 9 in 66% overall yield. Selective protection of the primary alcohol as the silyl ether and oxidation of the free secondary hydroxyl group gave the unsaturated keto ester 10 (78%). Ester 10 was condensed with ethylidene triphenyphosphorane and reduced to afford a 66% yield of a mixture of dienes 11. Upon NMR analysis, this material was established to be a mixture of the desired and (Z,Z)-isomers (5.7 1). Chromatographic separation led to... 

During heating to 150-220° C polyolefins isolate thermooxidative products of macromolecules with pronounced toxic properties, namely organic acids, ethers, unsaturated hydrocarbons, peroxide and carbonyl compounds (formaldehyde and acetaldehyde), carbon oxide and dioxide, etc. A mixture of such products of the thermooxidative destruction of polyolefins may result in acute chronic poisoning on inhalation. 

The methyl enol ether 37 is oxidized to the a,/3-unsaturated aldehyde 39 via hemiacetal 38. Unsaturated aldehyde 39, elongated one carbon from the aldehyde 36, is prepared by the Wittig reaction of 36 to give 37, and application of this reaction[ 88]. 

Allyllic ether 53 is oxidized regioselectively to the /3-alkoxy ketone 54, which is converted into the a,/i-unsaturated ketone 55 and used for annulation[99]. The ester of homoallylic alcohol 56 is oxidized mainlv to the 7-acetoxy ketone 57[99]. 

The 7, i5-unsaturated alcohol 99 is cyclized to 2-vinyl-5-phenyltetrahydro-furan (100) by exo cyclization in aqueous alcohol[124]. On the other hand, the dihydropyran 101 is formed by endo cyclization from a 7, (5-unsaturated alcohol substituted by two methyl groups at the i5-position. The direction of elimination of /3-hydrogen to give either enol ethers or allylic ethers can be controlled by using DMSO as a solvent and utilized in the synthesis of the tetronomycin precursor 102[125], The oxidation of the optically active 3-alkene-l,2-diol 103 affords the 2,5-dihydrofuran 104 in high ee. It should be noted that /3-OH is eliminated rather than /3-H at the end of the reac-tion[126]. 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

The highly ionic thaHic nitrate, which is soluble in alcohols, ethers, and carboxyhc acids, is also a very useful synthetic reagent. Oxidation of olefins, a,P-unsaturated carbonyl compounds, P-carbonyl sulfides, and a-nitrato ketones can aH be conveniently carried out in good yields (31,34—36). 

Crystallinity is low the pendent allyl group contributes to the amorphous state of these polymers. Propylene oxide homopolymer itself has not been developed commercially because it cannot be cross-baked by current methods (18). The copolymerization of PO with unsaturated epoxide monomers gives vulcanizable products (19,20). In ECH—PO—AGE, poly(ptopylene oxide- o-epichlorohydrin- o-abyl glycidyl ether) [25213-15-4] (5), and PO—AGE, poly(propylene oxide-i o-abyl glycidyl ether) [25104-27-2] (6), the molar composition of PO ranges from approximately 65 to 90%. 

These results the authors consider cannot be aeeounted for on the basis of a 6-membered ring B and the adoption of a 5- or 7-membered ring B introduces a difficulty in explaining the formation of 2 3 4 7-tetramethoxyphenanthraquinone in the oxidation of deaminocolchinol methyl ether. There is, however, a precedent in Weitzenbock s oxidation of 4 5 6 7-dibenzo-d -c /cZoheptatriene-l-aldehyde (X) to phenanthraquinone, for representing the a -unsaturated ketone as 9 12 13 14-tetramethoxy-3 4 5 6-dibenz-d -c /cZoheptatriene-7-one (XI CH2 at —> CO), using the system of numbering adopted by... 

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