Diallyl ether, metathesis

FIGURE 2. 50 MHz 13C NMR spectrum of the equilibrium products of metathesis reactions of diallyl ether catalysed by 8 (R = Me). Peaks 1 and 2 2,5-dihydrofuran. Peaks 3 and 4 linear polymer (ca 100% tram). Peaks a, b and c end-group carbons, a —CH2CH=CH2, b —CH2CH=CH2 and c -CH2CH=CH2- Solvent CDCI3. Reproduced by permission of Hiithig Wepf Publishers, Zug, Switzerland, from Ref. 262... 

Ring-closing metathesis (RCM) of the 6,6 -diallyl ether afforded macrocyclic alkenes,314 which can be reduced (H2/Pd) to saturated compounds with simultaneous removal of all benzyl protecting groups (Scheme 35).68... 

Efficient synthesis of 7- 20-iuembered crown ethers 122 having a trans-alkene bond was achieved by the Ru-catalysed metathesis of diallyl ethers 121 [46]. A remarkable... 

The effect of ethylene on the enantioselective RCM of triene 12 was probed by the addition of diallyl ether, which rapidly undergoes RCM to generate dihydrofuran and ethylene. Both the initial rate and initial enantioselectiv-ity for the formation of 13 were increased in the presence of diallyl ether (Scheme 10.24). Ethylene apparently allows the catalyst to enter a true Curtin-Hammett regime, wherein the catalyst diastereomer that leads to the minor enantiomer of the product can be epimerized by a degenerate metathesis reaction, leading to an increase in both rates and selectivity for the desired RCM process. 

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... 

Ethers were the first functionalized dienes to be polymerized successfully by ADMET [74]. It was found, however, that at least three methylene spacers between the oxygen atom and the olefin were required for successful polymerization with Schrock s catalysts. The resultant polymers were cross-linkable by both chemical and photochemical means [75]. Both [Mo]2 and [W]l were capable of producing the polymer, but polymerization with the molybdenum catalyst proceeded at a rate roughly 10 times faster than that with the tungsten catalyst [76]. ADMET polymerization of diallyl ether was attempted with both [Mo]2 and [Ru]l, resulting in a low molecular weight polymer. The major reaction product for both catalysts is 2,5-dihydrofuran, the result of RCM (Figure 13.6). Divinyl ether was not metathesis-active with any of Schrock s catalysts. 

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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