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Synthesis 1987; 1987(3): 314-317
DOI: 10.1055/s-1987-27932
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Synthesis of New Hetero-Annulated Coumarins: 2,3-Dihydro-4-oxothiapyrano [2,3-c]-benzopyran-2-ones, 4-Oxothiapyrano[2,3-c]-1-benzopyran-2-ones and 2-Oxo-3,4-dihydrobenzopyrano[4,3-b]-4-piperidones

J. A. M. van den Goorbergh* , M. van der Steeg, A. van der Gen
  • *Gorlaeus Laboratories, Department of Organic Chemistry, University of Leiden, P.O. Box 9502, NL-2300 RA Leiden, The Netherlands
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Publication Date:
12 September 2002 (online)

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2,3-Dihydro-4-oxothiapyrano[2,3-c]-1-benzopyran-2-ones 4 have been prepared by a double conjugate-addition of hydrogen sulfide to the divinyl ketone structure of 3-(1-oxoalkenyl)-1-benzopyran-2-ones 1. Subsequent oxidation of the hetero-annulated coumarins 4 with R2 = H afforded the 4-oxothiapyrano [2,3-c]-1-benzopyran-2-ones 7. 2-Oxo-3,4-dihydrobenzopyrano[4,3-b]-4-piperidones 8 were obtained by reaction of γ,δ-unsaturated β-oxoesters 2 with the N-methylimine derived from 2-hydroxybenzaldehyde. Compounds 4, 7 and 8 are the first representatives of new c-annulated coumarin ring systems.

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