Radical-mediated cyclisation of δ-aryl-β-dicarbonyl compounds to β-tetralones [3,4-dihydronaphthalen-2(1H)-ones]

Joanne F. Jamie, Rodney W. Rickards*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

δ-Aryl-β-dicarbonyl compounds carrying electron-releasing groups in the aromatic ring undergo efficient radical-mediated oxidative cyclisation to β-tetralones in the presence of four equivalents of manganese(III) acetate in acetic acid. Secondary oxidation invariably results in acetoxylation at the benzylic α-position of the initially-formed β-tetralones. Use of the oxidant cerium(IV) ammonium nitrate in methanol affords the corresponding α-methoxylated β-tetralones. The α-acetoxy-α-acyl-β-tetralones, but not their α-acetoxy-α-alkoxycarbonyl analogues, are aromatised in high yield on treatment with alkaline silica gel, providing an effective synthetic entry to appropriately substituted β-naphthols. The possible involvement of such radical-mediated intramolecular annulations of δ-aryl β-diketone intermediates in the biosynthetic formation of the second carbocyclic ring of the naphthalenoid ansamycin antibiotics is discussed in relation to the previously proposed Michael addition mechanism.

Original languageEnglish
Pages (from-to)2603-2613
Number of pages11
JournalJournal of the Chemical Society - Perkin Transactions 1
Issue number21
Publication statusPublished - 7 Nov 1996
Externally publishedYes

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