Claisen rearrangement over the past nine decades.

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

This article surveys variants of the Claisen rearrangement that are of general use in stereoselective organic synthesis. Recent results concerning the influence of steric and electronic parameters on transition state geometries are highlighted. The impact of the Claisen methodology in modern synthetic strategy and its application for the preparation of highly functionalized derivatives is exemplified.

Charles Girard

Papers

The ortho-Claisen Rearrangement. I. The Effect of Substituents on the Rearrangement of Allyl p-X-Phenyl Ethers1,2

The Reaction of 3-Phenyl-1-butene-3-14C with Formic Acid1,2