Diallyl ether, isomerization

Dialkynyl ligands, in platinum(II) complexes, 8, 545 iV,iV-Diallylamine, via allyindium reagents, 9, 703-704 Diallyl clusters, in trirutheniums and triosmiums, 6, 773 gem-Diallyl esters, via indium-mediated allylation, 9, 677 Diallyl ethers, isomerization, 10, 90 Diamagnetic ylides, with gold(II), 2, 278 Diamides... 

Alkenes with two reactive carbon-carbon double bonds per molecule like 1,5-hexadiene or diallyl ether are used in the synthesis of silicone compounds which can be later crosslinked by hydrosilylation. A sufficiently high excess of double bonds helps to prevent the dienes from taking part in silane addition across both olefmic ends, but trouble comes from double bond isomerization (Eq. 2). 

Y represents an oxygen atom or a single chemical bond. In the case of diallyl ether double bond isomerization occurs to a considerably higher extent, easily reaching 20 - 30 mole percent [9]. Obviously, reactive terminal C=C double bonds are required to get fast reaction with hydrosiloxane crosslinkers, whereas isomeric inner double bonds exhibit too low a reactivity to be of importance. Another strategy may be helpful. 

During the study of the isomerization of diallyl ether with catalysts of this type, it was observed that the nature of the complex anion (Y) has a profound influence on the relative rate of isomerization with respect to cyclization. Diallyl ether can be isomerized to a mixture consisting mainly of allyl propenyl ethers (44) with a small amount of 2-methyl-3-methylene-tetrahydrofuran (45) and dipropenyl ether (46) the catalyst for this... 

The stereoselective isomerization of unsymmetrical diallyl ethers to allyl ( )-vinyl ethers was also carried out in the presence of a cationic iridium(l) catalyst. The catalyst prepared in situ by treating [Ir(cod)(PPh2Me)2]PF6 with hydrogen was found to be an excellent catalyst for the selective isomerization of a less substituted allyl group to an ( )-vinyl ether (Scheme 44).72... 

Reaction of benzyl 4-O-benzyl-a-L-talopyranoside [142] and methyl 4,6-O-benzyli-dene-p-D-glucopyranoside [140] was less regioselective, giving 54% and 66%, respectively, of the 3-allyl ethers. No diallyl ethers were formed and no starting material remained, the rest being the isomeric 2-allyl ether. In both cases, tetrabutylammonium bromide was used to catalyze the reaction of the 2,3-O-dibutylstannylene intermediate with allyl bromide. 

Metal-catalyzed isomerization of unsymmetrical diallyl ethers is a unique route to synthesize allyl vinyl ethers for the Claisen rearrangement. In 1977, Reuter and Salomon reported that heating the diallyl ether 23 in the presence of a catalytic amount of tris(triphenylphosphine)ruthenium(II) dichloride resulted in the... 

In accessing chiral allyl vinyl ethers for Claisen rearrangement reactions, Nelson et al. employed the iridium-mediated isomerization strategy. Thus, the requisite enantioenriched diallyl ether substrate 28 was synthesized via a highly enantioselective diethylzinc-aldehyde addition protocol10 (Scheme 1.1k). The enantioselective addition of Et2Zn to cinnamaldehyde catalyzed by (—)-3-exo-morpholinoisobomeol (MIB 26)11 provided an intermediate zinc alkoxide (27). Treatment of 27 with acetic acid followed by 0-allylation in the presence of palladium acetate delivered the 28 in 73% yield and 93% ee. Isomerization of 28 with a catalytic amount of the iridium complex afforded the allyl vinyl ether... 

Under much more drastic conditions, at 200 °C RuCl2(PPh3)3 promotes the isomerization of diallyl ethers into aldehydes [66], and under 50 bar of... 

Unsymmetrical diallyl ethers, like their propargyl allyl counterparts, can theoretically yield isomeric 2,3-rearrangement products depending upon the site of deprotonation. In the first systematic study of... 

In the experiments using El-dj- and 3,3-d2-allyl alcohol in the presence and absence of pyridine bases, the results (Table IV) show that reaction occurs on Bronsted acid sites (Scheme 8), which results in diallyl ether formation with scrambling of the deuterium label via carbonium ion formation, and also on oxidizing sites on which both 1-d- and 3,3-d2-acrolein form via the formation and interconversion of the two isomeric 1,1 -d2- and 3,3-d2-allyl molybdates (27). These mechanisms are supported by data (Table IV) that show the suppression of ether formation and reduction of deuterium scrambling in the presence of base, which has little effect on the acrolein yield. The oxidation of O-allyl alcohol to acrolein over MOO3, which... 

Isomerization. Catioi unsymmetrical diallyl ether ncluding an access to y-is ithers to 7,8-unsaturated cai... 

Isomerization. Cationic iridium complex effects selective isomerization of unsymmetrical diallyl ethers and conjugated boronates containing an allylic ether group, including an access to 7-(siloxy)allylboronic esters. The conversion of allyl homoallyl ethers to -y,8-unsaturated carbonyl compounds is promoted by [(cod)IrCl]2. 

Two reviews have appeared this year on applications of the Claisen rearrangement of allyl vinyl ethers in synthesis. Diallyl ethers (58) have been shown to undergo a Ru"-catalysed rearrangement to (60), presumably via isomerization to the allyl vinyl ethers (59) and subsequent Claisen rearrangement (Scheme 43). This... 

Miyaura has reported the iridium-catalyzed isomerization of unsymmetrical dia-Uyl ethers to ( )-allyl vinyl ethers [20]. The iridium catalyst 12 active for the isomerization of diallyl ethers was prepared in situ by bubbhng hydrogen into a red solution of [Ir(cod)(PPh2Me)2]PF(5 by the method reported by FeUdn (Eq. 3.1.11)... 

Consequently, Grubbs and coworkers [58] have investigated the use of additives to control the distribution of products from metathesis and isomerization (Schemes 12.31 and 12.32). For example, when the RCM of diallyl ether 101... 

A reaction closely related to the above isomerization reactions is that of cyclization of diallyl ether ... 

In the presence of appropriate ruthenium catalyst precursors, diallyl and allyl homoallyl ethers do not lead to the expected metathesis or cycloisomerization products, but undergo first isomerization to form allyl vinyl ethers, and then a Claisen rearrangement which gives unsaturated aide-... 

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