Säurekatalysierte Dienon‐Phenol‐Umlagerungen von Allylcyclohexadienonen; ladungsinduzierte und ladungskontrollierte sigmatropische Reaktionen

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Abstract
The rearrangement of 10‐allyl‐2‐oxo‐Δ1(9), 3‐hexahydronaphthalene (12) catalysed by trifluoroacetic acid and other Bronsted acids yielded almost exclusively the [3s, 3s]‐products, 1‐ and 3‐allyl‐5,6,7,8‐tetrahydro‐2‐naphthol (16 and 15, respectively). The rearrangement of 12 with trifluoroacetic anhydride or acetic anhydride/sulfuric acid, yields, besides 15 and 16, appreciable amounts of the [1s, 2s]‐rearrangement product, 4‐allyl‐5,6,7,8‐tetrahydro‐2‐naphthol (14) (table 1).The CF3COOH catalysed dienone‐phenol‐rearrangement of 6‐ally‐5,6‐dimethyl‐cyclohexa‐2,4‐dien‐l‐one (11) in hexane at 0° yields4‐allyl‐2,3‐dimethyl‐phenol (19). Rearrangement of d3‐ll containing a specifically deuteriated allyl group proves that the formation of d3‐19 occurs via a [3s, 3s]‐sigmatropic reaction. On the other hand, treatment of 11 with (CF3CO)2O at 0° in hexane gives (after saponification) 4‐allyl‐, 5‐allyl‐ and 6‐allyl‐2,3‐dimethyl‐phenol (19, 20 and 21, respectivcly). This reaction occurs via an acyloxybenzenium‐ion intermediate. The reactions performed with d3‐11 demonstrate that the formation of d3‐19 occurs both by a direct [3s, 3s]‐shift and by a twofold [1s, 2s]‐shift, respectively. d3‐20 is formcd by a [3s, 4s]‐sigmatropic reaction. d3‐21 is obtained with about 95% inversion of the carbon skeleton of the allyl group. Thus d3‐21 is mainly formed by a [1s, 2s]‐ followed by a [3s, 4s]‐sigmatropic rearrangement.6‐Allyl‐6‐niethyl‐cyclohexa‐2,4‐dien‐1‐one (4) yields with CF3COOH in hexane 4‐allyl‐2‐methyl‐phenol (5), whereas with (CF3CO)2O in hexane 5, 3‐allyl‐ and 5‐allyl‐2‐methyl‐phenol (24 and 25, respectively) are formed in comparable amounts. As a minor product 6‐allyl‐2‐methyl‐phenol (26) was observed.Based on these observations, the concept of charge‐induced, e.g. schemes 2 and 3, and charge‐controlled, e.g. scheme 7, sigmatropic reactions, has been elaborated. In the former, the charge serves only to accelerate appreciably thermal orbital‐symmetry allowed reactions, whereas in the latter, the charge determines the course of the transformations according to the Woodward‐Hoffmann rules.Especially in acetylating systems, allylcyclohexdienones undergo charge‐induced and charge‐controlled reactions simultaneously.