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Updated: Jul 4, 2025

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Enantioselective [3 + 3] Annulation-Deoxalation Strategy for Rapid Access to δ-Oxoesters via N-Heterocyclic Carbene
Izabela Barańska1, Liliana Dobrzańska1, Zbigniew Rafiński1
1Faculty of Chemistry, Nicolaus Copernicus University in Torun, 7 Gagarin Street, 87-100 Torun, Poland.
Abstract:
A new and unprecedented stereoselective synthetic approach to δ-oxoesters derivatives from readily available starting materials has been developed. This method, catalyzed by N-heterocyclic carbene, involves an annulation-deoxalation reaction of alkynyl aldehydes with 2,4-diketoesters and proceeds via the chiral α,β-unsaturated acylazolium intermediates. The annulation includes the in situ formation of dihydropyranones, which undergo ring-opening methanolysis with Lewis acid activation, followed by deoxalation to afford chiral 1,5-ketoesters in moderate to good yields.
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