Baseninduzierte umlagerungen von 3,9 dioxatricyclo[3.3.1.02,4]nonan-7-onen zu m-hydroxyphenylcarbonyl-verbindungen

8-Oxabicyclo3.2.1]oct-6-en-3-ones (5), easily available by 4+3]cycloaddition, were epoxidised at the CC double bond. The 3,9-dioxatricyclo3.3.1.0^2,4]nonan-7-ones (6) thus obtained are rearranged on treatment with sodium ethoxide in ethanol to form 3-hydroxybenzaldehydes (8a-d) and 3-hydroxy-2,4,5-trimethylacetophenone (8e) in good yields. As intermediates of these rearrangements, 8-hydroxy-6-oxatricyclo 3.2.1.0^2,7]octan-3-ones are postulated ; the trimethyl derivative 7g and the 6-carba-derivatives 4a,b could be isolated.