Vinyl allyl

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 ... 

A variant of the Nazarov reaction is the cyclization of allyl vinyl ketones 8. These will first react by double bond isomerization to give divinyl ketones, and then cyclize to yield a cyclopentenone 9 bearing an additional methyl substituent ... 

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. 

Chiral modification of diorganomagnesium compounds with the dilithium salt oi (S)-l,l -bi-naphthalene-2,2 -diol gave reagents with the empirical formula 30. Good to excellent enantiose-lectivities were observed in addition reactions of aliphatic and aromatic reagents to aromatic aldehydes30,31, however, the selectivities were not satisfactory with allylic, vinylic and acetylenic reagents. 

King and Harding296 have reported an interesting Sulfo-Cope rearrangement, and have presented evidence for the formation of the unstable sulfene (142) during the gas or liquid phase thermal [3,3]sigmatropic rearrangement of allyl vinyl sulfone (equation 88). 

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