2, 6-Dimethylphenyl propargyl ether (10) and its derivatives 12–15 rearrange thermally to 1, 5-dimethyl-6-methylene-tricyclo [3.2.1.02,7]oct-3-en-8-one (9) and related compounds 16–19. The ethers undergo first an aromatic [3, 3]-sigmatropic rearrangement to ortho-allenyldienones 11, which then undergo ring closure to the tricyclic products by an electrocyclic reaction.



Only in the case of the γ-methylpropargyl ether 13, the ortho-dienone 11 is further rearranged in low yield to the para-butynylphenol 20, but the tricyclic ketone 17 is again the main product.



New data show that the known thermal cyclisation of aryl propargyl ethers to chromenes (e. g. 4 8) involves a preliminary [3, 3]-sigmatropic rearrangement.

Sigmatropische Umlagerungen von Aryl‐propargyläthern; Synthese von 1, 5‐Dimethyl‐6‐methylen‐tricyclo[3, 2, 1, 02,7]‐oct‐3‐en‐8‐on‐Derivaten. Vorläufige Mitteilung

[3,3]-Sigmatropic rearrangements of fluorinated compounds

A concise preparation of tetrasubstituted hindered functionalized CF3-olefins 2−7 from corresponding enol ether 3 is described. Geometrically pure γ-CF3,γ-alkyl allylic alcohols thus prepared could undergo Claisen-type rearrangements and provide, in good yields, carboxylic esters and amides containing a β- quaternary CF3-substituted carbon.

Short stereoselective route to gamma-CF3 allylic alcohols: rearrangements with creation of quaternary CF3-substituted carbons

Since the first observation of a thermal rearrangement vinyl allyl ether to the corresponding homoallylcyclic carbonyl compound by Claisen in 1912, rearrangements of vinyl and aryl allylic ethers have been extensively studied and exploited for their synthetic value. The corresponding rearrangement of substituted 1,5-hexadiene was first recognized by Cope in 1940 as the carbon analog of the Claisen rearrangement. Today it is recognized that such transformations fall within the general category of a [3,3] sigamtropic reaction and that considerable variation may be accommodated in the basic requirement of a system of six atoms with terminal unsaturated linkage. This chapter attempts to survey the vas t accumulation of Claisen and Cope rearrangements recorded since the first coverage in 1944.


Keywords:

Claisen rearrangments;
Cope rearrangements;
allyl ethers;
aliphatic rearrangements;
anomalies;
amine rearrangements;
thio rearrangements;
migration;
experimental procedures

C.G. Krespan

Papers

Negative substituents in the claisen rearrangement