Ethers, unsaturated epoxidation

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%. 

Allylic bromides 383 and 384 were the relais substances for the synthesis of coriamyrtin (9) (Scheme 43). The allylic bromides were eliminated with potassium ferf-butoxide in toluene affording diene 387. 1,4-Addition with W-bromosuccini-mide in polar solvent at room temperature yielded the unsaturated a-bromo-5-hydroxy unit of 388, which formed the unsaturated epoxide 389 by base treatment. Epoxidation with peracid occurred as expected from the convex face. The cyclic ether moiety of bisepoxide 390 was oxidized to the lactone 368 with ruthenium... 

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. 

Suitably positioned carbonyl groups may cause ring closure, leading to either five- or six-membered ring lactones. BF3 etherate proved to be more selective than protic acids in a study of unsaturated epoxides, giving exclusively the larger ring size, as illustrated in equation (75). ... 

Organofunctional epoxysilanes may be prepared by hydrosilylating unsaturated epoxides or epoxidized unsaturated silanes. The hydrosilylation of allyl ethers CH2=CHCH20R is commonly used for synthesis (e.g., y-glycidoxytrimethoxysilane) as follows ... 

In addition to the diglycidyl ether based resins, there are also non-glycidyl ether based epoxide resins. These materials can usually be prepared by carrying out an epoxidisation reaction on an unsaturated compound using hydrogen peroxide or peracetic acid ... 

The polymerization o oxetanes with cationic catalysts has been studied by many investigators. (1.H2) RoseC. ), in particular, first reported the homopolymerization of the parent compound, tri-methylene oxide (TMO), with a Lewis acid catalyst, boron trifluoride. The use of coordination catalysts to polymerize oxetanes has been reported in the patent literature by Vandenberg.W In this work, Vandenberg polymerized oxetanes with the aluminum trialkyl -water-acetylacetone coordination catalyst (referred to as chelate catalyst) that he discovered for epoxide polymerization . This paper describes the homo- and co-polymerization of TMO with these coordination catalysts. Specific TMO copolymers, particularly with unsaturated epoxides such as allyl glycidyl ether (AGE), are shown to provide the basis for a new family o polyether elastomers. These new elastomers are compared with the related propylene oxide-allyl glycidyl ether (PO-AGE) copolymer elastomers. The historical development and general characteristics of polyether elastomers and, in particular, the propylene oxide elastomers, are reviewed below. 

Reductions - For unsaturated compounds containing oxygen (allylic alcohols and ethers, ynols, epoxides, a,6-unsaturated ketones, aldehydes, acids and epoxides) nidkel boride (prepared from N1 acetate and NaBH ) selectively and quantitatively hydrogenates the C-C double bonds without rearrangements, hydrogenolysis or carbonyl reductions. 

TMO with these coordination catalysts. Specific TMO copolymers, particularly with unsaturated epoxides such as allyl glycidyl ether (AGEJ, are shown to provide the basis for a new family of polyether elastomers. These new elastomers are compared with the related propylene oxide-allyl glycidyl ether (PO-AGE) copolymer elastomers. The historical development and general characteristics o polyether elastomers and, in particular, the propylene oxide elastomers, are reviewed below. 

The hydrogenolyaia of cyclopropane rings (C—C bond cleavage) has been described on p, 105. In syntheses of complex molecules reductive cleavage of alcohols, epoxides, and enol ethers of 5-keto esters are the most important examples, and some selectivity rules will be given. Primary alcohols are converted into tosylates much faster than secondary alcohols. The tosylate group is substituted by hydrogen upon treatment with LiAlH (W. Zorbach, 1961). Epoxides are also easily opened by LiAlH. The hydride ion attacks the less hindered carbon atom of the epoxide (H.B. Henhest, 1956). The reduction of sterically hindered enol ethers of 9-keto esters with lithium in ammonia leads to the a,/S-unsaturated ester and subsequently to the saturated ester in reasonable yields (R.M. Coates, 1970). Tributyltin hydride reduces halides to hydrocarbons stereoselectively in a free-radical chain reaction (L.W. Menapace, 1964) and reacts only slowly with C 0 and C—C double bonds (W.T. Brady, 1970 H.G. Kuivila, 1968). 

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). 

Telomerization Reactions. Butadiene can react readily with a number of chain-transfer agents to undergo telomerization reactions. The more often studied reagents are carbon dioxide (167—178), water (179—181), ammonia (182), alcohols (183—185), amines (186), acetic acid (187), water and CO2 (188), ammonia and CO2 (189), epoxide and CO2 (190), mercaptans (191), and other systems (171). These reactions have been widely studied and used in making unsaturated lactones, alcohols, amines, ethers, esters, and many other compounds. 

Although the first and still most important epoxide resins are of the glycidyl ether type, other epoxide resins have been commercially marketed in recent years. These materials are generally prepared by epoxidising unsaturated compounds using hydrogen peroxide or peracetic acid. 

Hodgson and coworkers extended this concept to epoxides of unsaturated cyclic ethers 128 [5] and amines 130 [46, 47] (Scheme 5.28). It is interesting that the use of trimethylsilylmethyllithium as the organolithium in this case resulted in substituted allylsilanes 129 and 131 (R = CH2SiMe3) presumably the epoxide ring protons of 128 and 130 are more acidic than those of a simple terminal epoxide (see Scheme 5.26). 

In a formal synthesis of fasicularin, the critical spirocyclic ketone intermediate 183 was obtained by use of the rearrangement reaction of the silyloxy epoxide 182, derived from the unsaturated alcohol 180. Alkene 180 was epoxidized with DMDO to produce epoxy alcohol 181 as a single diastereoisomer, which was transformed into the trimethyl silyl ether derivative 182. Treatment of 182 with HCU resulted in smooth ring-expansion to produce spiro compound 183, which was subsequently elaborated to the desired natural product (Scheme 8.46) [88]. 

When analysing these different lists one realises that the different sources do not agree with each other. So far as the NFPA reactivity code is concerned, codes 2 and 3 have been attributed to epoxides and ethers that are unsaturated. Their purpose is to inform the reader about dangerous polymerisation and not peroxidation risks. The accidents described below also involve compounds such as dibutyl ether that are not considered as dangerous in the regulations or NFPA Extracting a fatty substance and a floor wax with diethyl ether gives rise to a detonation. 

Increasing use is being made of pyran syntheses based upon [4 + 2] cycloadditions of carbonyl compounds. The appropriate unsaturated aldehyde with ethyl vinyl ether yields 53 with peracids this affords an epoxide that undergoes ring contraction to the aldehyde 54 (Scheme 23) and rhodium catalyzed decarbonylation affords the required 3-alkylfuran with the optical center intact.116 Acetoxybutadiene derivatives add active carbonyl compounds giving pyrans that contract under the influence of acids to give... 

Asymmetric epoxidation of a,jS-unsaturated ketones represents an efficient method for the preparation of optically active a,jS-epoxy ketonesJ Recently, a new and very efficient catalytic system for enantioselective epoxidation of ( )-a,jS-enones to the corresponding trans-epoxy ketones has been developed based on a BlNOL-zinc complexJ Very high yields and excellent diastereo- and enantioselectivities are achieved at room temperature using cumene hydroperoxide (CMHP) as the terminal oxidant and performing the reaction in diethyl ether. A combination of enantio-merically pure BINOL and diethylzinc readily affords the active catalyst in situ (Figure 6.13). ... 

The preparation of 1 started with the addition of lithiated 4 to the enantiomcrically-pure epoxide 5, which was prepared from the racemate using the Jacobsen protocol. Reduction followed by selective protection of the primary alcohol gave the monosilyl ether, which was further protected with MOM chloride to give 7. Pd-mediated oxidation to the methyl ketone followed by condensation with the Horner-Emmons reagent gave the unsaturated ester 8 as an inconsequential mixture of geometric isomers. Oxidation then set the stage for the crucial cyclization. 

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