Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence

Ramani Gurubrahamam, Bing Fong Gao, Yan Ming Chen, Yu Te Chan, Ming-Kang Tsai, Kwunmin Chen

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20 Citations (Scopus)

Abstract

An efficient organocatalytic reaction using 1,3-nitro enynes with 4-hydroxycoumarin and 4-hydroxy-6-methyl-2-pyrone to afford pyrano-annulated scaffolds in high yield (up to 88% yield) and excellent stereoselectivities (up to >20:1 dr and >99% ee) is described. The reaction proceeded through sequential conjugate addition, allene formation, intramolecular oxa-Michael 6-endo-dig cyclization and DABCO-catalyzed olefin isomerization. A kinetic profile for isomerization was established. The mechanism for the organocascade reaction was proposed according to requisite computational and mechanistic experimental studies.

Original languageEnglish
Pages (from-to)3098-3101
Number of pages4
JournalOrganic Letters
Volume18
Issue number13
DOIs
Publication statusPublished - 2016 Jul 1

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ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry

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