Nucleophilicity of 4-(Alkylthio)-3-imidazoline Derived Enamines

Hensinger, Magenta J.; Eitzinger, Andreas; Trapp, Oliver und Ofial, Armin R. (2024): Nucleophilicity of 4-(Alkylthio)-3-imidazoline Derived Enamines. In: Chemistry - A European Journal, Vol. 30, No. 2, e202302764

Abstract

Imidazolidine-4-thiones (ITOs) are cyclic, secondary amines that were considered as potential prebiotic organocatalysts for lightdriven α-alkylations of aldehydes by bromoacetonitrile (BAN). Recent studies showed that the initially supplied ITOs represent the pre-catalyst because they undergo S-alkylation with BAN to give 4-(alkylthio)-3-imidazolines (TIMs). Given that the same reagent mix that undergoes light-driven α-alkylations is also effective in the dark, we synthesized ten ITO- or TIM-derived enamines of aldehydes and characterized their nucleophilic reactivities by kinetic studies in acetonitrile. The experimental second-order rate constants k2 for reactions of enamines with benzhydrylium ions (reference electrophiles) were evaluated by the Mayr-Patz equation, lg k2(20 °C)=sN(N+E). The determined nucleophilicities N (and sN) reveal the reactivity profiles of these enamines under prebiotically relevant conditions as well as their potential for use in organocatalytic synthesis.

• Item Type: Journal article
• EU Funded Grant Agreement Number: 101024710
• EU Projects: Horizon 2020 > Marie Skłodowska Curie Actions > Marie Skłodowska-Curie Individual Fellowships > 101024710: SImCat - Imidazolidinethiones: Underexplored organocatalysts that show promise in catalyzing prebiotic and modern organic reactions
• Keywords: enamines; kinetics; linear free energy relationships; quantum-chemical calculations; thermodynamics
• Faculties: Chemistry and Pharmacy > Department of Chemistry
• Subjects: 500 Science > 540 Chemistry
• ISSN: 0947-6539
• Language: English