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- Title
Säurekatalysierte Dienon-Phenol-Umlagerungen von Allylcyclohexadienonen; ladungsinduzierte und ladungskontrollierte sigmatropische Reaktionen.
- Authors
Widmer, U.; Zsindely, J.; Hansen, Hans-Jürgen; Schmid, Hans
- 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 [3 s, 3 s]-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 [1 s, 2 s]-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 [3 s, 3 s]-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 [3 s, 3 s]-shift and by a twofold [1 s, 2 s]-shift, respectively. d3- 20 is formcd by a [3 s, 4 s]-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 [1 s, 2 s]- followed by a [3 s, 4 s]-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.
- Publication
Helvetica Chimica Acta, 1973, Vol 56, Issue 1, p75
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19730560104