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Experiments on the total synthesis of Lysolipin I. Part III. Preparation and transformations of substituted 1,2,3,4-Tetrahydrodibenzofuran-1-ones

✍ Scribed by Rudolf O. Duthaler; Veronica Scherrer

Publisher
John Wiley and Sons
Year
1984
Tongue
German
Weight
635 KB
Volume
67
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

1,2,3,4‐Tetrahydrodibenzofuran‐1‐ones were obtained by Michael addition of 1,3‐cyclohexadione (2) to o‐benzoquinone (3) and to p‐benzoquinones 8 and 11 (Scheme 2). In addition to the expected 7,8‐disubstituted adduct 14, the ZnCl~2~‐catalyzed reaction of dione 2 with methoxy‐p‐benzoquinone (11) afforded a small amount of the 6,8‐disubstituted regio‐isomer 13 (Scheme 2). The projected cleavage of these dibenzofuranones to 3‐methoxy‐2‐phenyl‐2‐cyclohexenone 22 could be effected by treatment with NaOH followed by methylation (Scheme 3). Attempted acetalization of such dibenzofuranones resulted in a retro‐Claisen‐type cleavage, giving the benzofuryl‐butyrate 16. Other transformations include reduction of the ketone, of the C(4a)=C(9b) bond, and alkylation with Li‐ethoxyacetylide (Scheme 3). Oxidation of 8‐hydroxy‐7‐mehoxydibenzofuran derivatives led to o‐quinones instead of the desired ring cleavage to p‐quinones (Scheme 4).

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