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

Publisher Website
Google Scholar
Abstract
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.