Ethers allyl phenyl, sigmatropic rearrangement

Claisen rearrangement (Sections 18.4 and 30.8) the thermal [3.3] sigmatropic rearrangement of an allyl vinyl ether or an allyl phenyl ether. 

Oxopentanals may be synthesized from allylic alcohols by 3,3 sigmatropic rearrangement of their vinyl ethers, and subs uent oxidation of the terminal double bond. Cinnamyl alcohol (31) was converted to the allyl vinyl ether (32), which was subjected to Qaisen reairangement to give 3-phenyl-4-pentenal (33) in 50% yield. Oxidation of the terminal double bond of (33) gave 3-phenyl-4-oxopentanal... 

Allyl phenyl ethers undergo an intramolecular [3,3]-sigmatropic rearrangement (the Claisen rearrangement) to form the C-alkyl derivative (Scheme 4.18). A consequence of the electrocyclic mechanisms is that the y-carbon atom of the allyl ether becomes attached to the aromatic ring. 

Sigmatropic rearrangement of allyl vinyl ether substrates usually requires heating at around 200 . Allyl phenyl ether rearranges at room temperature in the presence of Lewis acid reagents, which have, however, turned out to be ineffective with aliphatic ethers. The concept of "combined acid-base attack previously mentioned (18,19) has motivated several successful experiments as shown in Schemes 10 through 12 (20). 

The thermal rearrangement of allyl phenyl ethers to o-allyl phenol and its mechanism is very well known to organic chemists. Both the aliphatic and aromatic Claisen rearrangements involve a 3,3-sigmatropic shift. There are reviews providing usefulness of this rearrangement reaction. ... 

Thermal [3,3]-sigmatropic rearrangements of allyl aryl ethers and allyl vinyl ethers are known as the Claisen rearrangements [68], These reactions are sensitive to solvent polarity and the rates of the reactions are increased by increasing the solvent polarity [69]. The simplest examples are the thermal conversion of allyl phenyl ether to ort/io-allyl phenol and of allyl vinyl ether to 4-pentenal [70]. 

Claisen rearrangements of allyl phenyl ethers to ortho-a y phenols were the first [3,3]-sigmatropic rearrangements to be thoroughly studied. The reaction... 

A new site-selective dehydration can convert allylic alcohols (64) and (66) into the dienes (65) and (67) respectively, using 2,4-dinitrobenzenesulphenyl chloride in triethylamine. The intermediate selenenate ester presumably undergoes [2,3] sigmatropic rearrangement to the allyl selenoxide, which then fragments to the diene. Palladium diacetate-triphenylphosphine appears to be an effective catalyst for the elimination of acetic acid or phenol from allylic acetates or phenyl ethers respectively, leading to 1,3-dienes in high yield. ... 

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