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Koch R, Blanch RJ, Wentrup C. Ketene-ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4,6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and Wolff rearrangement to fulven-6-one. J Org Chem. 2014;79(15):6978-86doi: 10.1021/jo5011087.
Koch, R., Blanch, R. J., & Wentrup, C. (2014). Ketene-ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4,6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and Wolff rearrangement to fulven-6-one. The Journal of organic chemistry, 79(15), 6978-86. https://doi.org/10.1021/jo5011087
Koch, Rainer, et al. "Ketene-ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4,6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and Wolff rearrangement to fulven-6-one." The Journal of organic chemistry vol. 79,15 (2014): 6978-86. doi: https://doi.org/10.1021/jo5011087
Koch R, Blanch RJ, Wentrup C. Ketene-ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4,6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and Wolff rearrangement to fulven-6-one. J Org Chem. 2014 Aug 01;79(15):6978-86. doi: 10.1021/jo5011087. Epub 2014 Jul 11. PMID: 24988224.
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J Org Chem. 2014 Aug 01;79(15):6978-86. doi: 10.1021/jo5011087. Epub 2014 Jul 11.

Ketene-ketene interconversion. 6-Carbonylcyclohexa-2,4-dienone-hepta-1,2,4,6-tetraene-1,7-dione-6-oxocyclohexa-2,4-dienylidene and Wolff rearrangement to fulven-6-one.

The Journal of organic chemistry

Rainer Koch, Rodney J Blanch, Curt Wentrup

Affiliations

  1. Institut für Chemie and Center of Interface Science, Carl von Ossietzky Universität Oldenburg , P.O. Box 2503, 26111 Oldenburg, Germany.

PMID: 24988224 DOI: 10.1021/jo5011087

Abstract

6-Carbonylcyclohexa-2,4-dienone (1) has been generated by flash vacuum thermolysis (FVT) with Ar-matrix isolation of methyl salicylate (7), 2-phenylbenzo-1,3-dioxan-4-one (8), phthalic peranhydride (9), and benzofuran-2,3-dione (11) and also by matrix photolysis of 9, 11, and 2-diazocyclohepta-4,6-dien-1,3-dione (12). In each case, FVT above 600 °C results in decarbonylation of 1 and Wolff rearrangement to fulven-6-one (13) either concertedly or via open-shell singlet 6-oxocyclohexa-2,4-dienylidene (18). Ketenes 1 and 13 were characterized by IR spectroscopy. Photolysis of matrix-isolated 1 at 254 nm also results in the slow formation of 13. The sequential formation of ketenes 1 and 13 from 7 has also been monitored by FVT-mass spectrometry, and 13 has been trapped with MeOH to afford methyl 1,3-cyclopentadiene-1- and -2-carboxylates 15 and 16. FVT of methyl salicylate-1-(13)C 7a revealed a deep-seated rearrangement of the (13)C-labeled 1a to hepta-1,2,4,6-tetraen-1,7-dione (17a) by means of electrocyclic ring opening followed by a facile 1,5-H shift and recyclization prior to CO-elimination and ring contraction to (13)C-labeled 13. The rearrangement mechanism is supported by M06-2X/6-311++G(d,p) calculations, which predict feasible barriers for the FVT rearrangements and confirm the observed labeling pattern in the isolated methyl salicylate 7a/7b and methyl cyclopentadienecarboxylates 20 and 21 resulting from trapping of 13 with MeOH.

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