Syntheses of 6,7‐benzotropolone by using ring‐closing metathesis variants obviating a strongly acidic hydrolysis thereafter

Abstract: A Wittig reaction of 3-hydroxyphtalide (11) gave ortho-styrene-2-carboxylic acid (12). Its Weinreb amide 13 acylated heterosubstituted methyllithiums. This led to aryl “methyl” ketones whose sp3-carbon was substituted by Cl+OMe (in 14 a), 2×Cl (in 14 b), OtBu (in 17 a), SPh (in 17 b) or SO2Ph (in 17 c). The enolates of these ketones were C-allylated. This furnished the benzene-fused nona-1,8-dienones 7 a–b and 9 a–c, respectively. Ring-closing metatheses provided the corresponding benzocycloheptadienones 8 a-b and 10 a–c. Their ketone moieties were α,α-disubstituted (in 8 a–b) or α-monosubstituted (in 10 a–c). Each substitution pattern allowed to generate the hydroxyenone motif of the corresponding benzocycloheptatrienone—or 6,7-benzotropolone—6 a: The MeO- and PhS-containing benzocycloheptadienone 8 a gave 6,7-benzotropolone methyl ether (15) by sulfoxide formation and pyrolysis; 15 was demethylated with BCl3. The same intermediate resulted from the dichlorobenzocycloheptadienone 8 b and NaOMe. The benzocycloheptadienone 10 a was de(tert-butylated) with formic acid; a subsequent Pfitzner-Moffatt oxidation completed 6,7-benzotropolone (6 a) once more. The PhS-containing benzocycloheptadienone 10 b was α-acetoxylated with Pb(OAc)4; the resulting O,S-acetal gave 6,7-benzotropolone (6 a) by hydrolysis. The PhSO2-containing substrate 10 c was deprotonated whereupon an oxidation with Me3Si−O−O−SiMe3 gave 6,7-benzotropolone (6 a)

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: European journal of organic chemistry. - 2022, 17 (2022) , e202101070, ISSN: 1099-0690

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2022
• Creator: Koblischek, Philip ; Brückner, Reinhard

Further information

• DOI: 10.1002/ejoc.202101070
• URN: urn:nbn:de:bsz:25-freidok-2266559
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:51 PM CET