Lactone Enolates of Isochroman-3-ones and 2‑Coumaranones: Quantification of Their Nucleophilicity in DMSO and Conjugate Additions to Chalcones

Mousavi, Mohammad S.; Di Mola, Antonia; Pierri, Giovanni; Tedesco, Consiglia; Hensinger, Magenta J.; Sun, Aijia; Wang, Yilan; Mayer, Peter ; Ofial, Armin R. und Massa, Antonio (30. April 2024): Lactone Enolates of Isochroman-3-ones and 2‑Coumaranones: Quantification of Their Nucleophilicity in DMSO and Conjugate Additions to Chalcones. In: Journal of Organic Chemistry, Bd. 89, Nr. 10: S. 6915-6928

Abstract

Owing to stereoelectronic effects, lactones often deviate in reactivity from their open-chain ester analogues as demonstrated by the CH acidity (in DMSO) of 3-isochromanone (pKa = 18.8) and 2-coumaranone (pKa = 13.5), which is higher than that of ethyl phenylacetate (pKa = 22.6). We have now characterized the reactivity of the lactone enolates derived from 3-isochromanone and 2-coumaranone by following the kinetics of their Michael reactions with p-quinone methides and arylidenemalonates (reference electrophiles) in DMSO at 20 °C. Evaluation of the experimentally determined second-order rate constants k2 by the Mayr–Patz equation, lg k2 = sN(N + E), furnished the nucleophilicity parameters N (and sN) of the lactone enolates. By localizing their position on the Mayr nucleophilicity scale, the scope of their electrophilic reaction partners becomes predictable, and we demonstrate a novel catalytic methodology for a series of carbon–carbon bond-forming reactions of lactone enolates with chalcones under phase transfer conditions in toluene.

• Dokumententyp: Zeitschriftenartikel
• EU Funded Grant Agreement Number: 101024710
• Keywords: Electrophiles; Enolates; Kinetics; Lactones; Reactivity
• Fakultät: Chemie und Pharmazie > Department Chemie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 0022-3263
• Sprache: Englisch