ZnI2-catalyzed diastereoselective [4 + 2] cycloadditions of β,γ-Unsaturated α-ketothioesters with olefins

Kanchan Mal, Supriya Das, Nakul C. Maiti, Ramalingam Natarajan, Indrajit Das

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36 Scopus citations


The potential of β, γ-unsaturated α-ketothioesters participating in hetero-Diels-Alder reaction has remained unexplored. We report herein the first study of a ZnI2-catalyzed highly diastereoselective inverse electron demand hetero-Diels-Alder reaction of β, γ-unsaturated α-ketothioesters with olefins to access highly substituted 3,4-dihydro-2H-pyrans. All the reactions proceed with cis-selectivity in moderate to excellent yields. Under similar reaction conditions, terminal alkynes undergo direct conjugate 1,4-addition to yield σ,-acetylenic α-ketothioesters. Furthermore, the utility of these cycloadducts has been demonstrated by an NBS-MeOH mediated stereospecific efficient access to fully substituted pyran rings. The product bromoethers undergo E2 elimination with DBU, resulting in substituted 3,6-dihydro-2H-pyrans. In addition, the thioester moiety of the products has been used for further transformations, such as amidations and Fukuyama coupling reactions.

Original languageEnglish
Pages (from-to)2972-2988
Number of pages17
JournalJournal of Organic Chemistry
Issue number6
StatePublished - 20 Mar 2015
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry


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