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Palladium(II)-Catalyzed Synthesis of 2H,3′H‑Spiro[benzofuran-3,2′-naphthoquinones]

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posted on 2013-09-06, 00:00 authored by Pieter Claes, Jan Jacobs, Bart Kesteleyn, Tuyen Nguyen Van, Norbert De Kimpe
2H,3′H-Spiro­[benzofuran-3,2′-naphthoquinones], constituting a new spiroheterocyclic skeleton, were synthesized starting from 2-aryloxymethyl-1,4-naphthoquinones by means of a palladium­(II)-catalyzed reaction, which is a new spirocyclic transformation. Under optimal conditions, i.e. 10 mol % of palladium­(II) acetate, 15 mol % of 3,5-dichloropyridine, and 5 mol % of trifluoroacetic acid in acetic acid at 110 °C, various 2H,3′H-spiro­[benzofuran-3,2′-naphthoquinones] were synthesized in yields strongly dependent on the substitution pattern of the aryloxy group. Unsubstituted or ortho-substituted 2-aryloxymethyl-1,4-quinones were found to rearrange toward the corresponding 2-(4-hydroxyaryl)-1,4-quinones upon treatment with trifluoroacetic acid.

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