Vinyl allyl ether

The procedure described illustrates a new general synthetic method for the preparation of (E)-3-allyloxyacryl ic acids and their conversion to a-unsubstituted y,5-unsaturated aldehydes by subsequent Claisen rearrangement-decarboxyl at ion. Such aldehydes are traditionally prepared by Claisen rearrangements of allyl vinyl ethers. Allyl vinyl ethers are typically prepared by either mercury-catalyzed vinyl ether exchange with allylic alcohols or acid-catalyzed vinylation of allylic alcohols with acetals. The basic conditions required for alkoxide addition to the betaine to produce carboxyvinyl allyl ethers, as described in this report, nicely complements these two methods. In addition, this Claisen rearrangement is an... 

Claisen rearrangement of allyl vinyl ethers. " Allyl vinyl ethers undergo Claisen rearrangement at 25° in CICHiCHiCl in the presence of 2 equiv. of (CjH liAlSQH, (prepared from triethylaluminum and thiophenol) or (C3H5)2AICI/P(CftH,),. 

Claisen Rearrangements - allyl vinyl ether to an y,5-unsaturated carbonyl... 

CLAISEN - IRELAND Rearrangment Rearrangement ol allyl phenyl ethers to o (or p-)allylphenols or of allyl vinyl ethers to y.S-unsaturated aldehydes or ketones (Claisen) Rearrangement ol allyl esters as enolale anions to y.S-unsaturated acids (Ireland)... 

Unimolecular reactions that take place by way of cyclic transition states typically have negative entropies of activation because of the loss of rotational degrees of freedom associated with the highly ordered transition state. For example, thermal isomerization of allyl vinyl ether to 4-pentenal has AS = —8eu. ... 

Table 12.3 Claisen rearangement of allyl vinyl ether to form 5-hexenal ...

Rearrangement of allyl vinyl ethers or allyl aryl ethers... 

The Claisen rearrangemenC is a thermal rearrangement of allyl aryl ethers and allyl vinyl ethers respectively. It may be regarded as the oxa-version of the closely related Cope rearrangement. Claisen has discovered this reaction first on allyl vinyl ethers 1, and then extended to the rearrangement of allyl aryl ethers 2 to yield o-allylphenols 3 ... 

Two other important sigmatropic reactions are the Claisen rearrangement of an allyl aryl ether discussed in Section 18.4 and the Cope rearrangement of a 1,5-hexadiene. These two, along with the Diels-Alder reaction, are the most useful pericyclic reactions for organic synthesis many thousands of examples of all three are known. Note that the Claisen rearrangement occurs with both allylic aryl ethers and allylic vinylic ethers. 

Ether groups, including vinyl ethers, allylic ethers, and thioethers are also compatible. 

Allyl vinyl ethers have been prepared using the ylide (101) but only from non-enolizable carbonyl compounds. The ethers rearrange on heating to give a-allyl aldehydes, e.g. (102). 

---