TheClaisen Rearrangement

Abstract

Allyl ethers of enols and phenols undergo rearrangement to C‐allyl derivatives when heated to sufficiently high temperatures. The reaction, named after its discoverer (Claisen, 1912) was first observed when ethyl O ‐allylacetonacetate was subjected to distillation at atmospheric pressure in the presence of ammonium chloride. The allyl ethers of phenols rearrange smoothly at temperatures of about 200°C in the absence of catalysts, Allyl ethers of ortho ‐disubstituted phenols rearrange to the corresponding p ‐allyphenols. The only known example of para rearrangement accompanied by inversion is the reaction of alpha‐ethylallyl 2‐carbomethoxy‐6‐methylphenyl ether. These rearrangements are discussed in detail.

Uncommon reaction in 4-formyl phenols – substitution of the formyl group

“…Al ready at the beginning of the last century, substitution not only of hydrogen but also of the carboxylic and formyl groups in allyl phenol ethers was observed. The reaction is known to proceed according to the Claisen rearrange ment mechanism at higher temperatures [1,2] (Scheme 1).…”

4,8-Bisallyl-2,6-dimethylnaphthalene-1,5-diyl Diacetate

“…[12] This led us to consider the double Claisen-rearrangement of 2,6-disubsubstituted bis allyl ethers of 1,5-naphthalenediols as a synthetic route to bisperisubstituted naphthols for subsequent uses for the synthesis of 1,6-dioxapyrenes.…”