Mechanistic insights into annulation of arylidene- [Delta] [sup] 2-pyrrolin-4-ones by cinchona squaramide-based organocatalystsCiber, Luka (Avtor) Ričko, Sebastijan (Avtor) Gregorc, Jure (Avtor) Požgan, Franc (Avtor) Svete, Jurij (Avtor) Brodnik, Helena (Avtor) Štefane, Bogdan (Avtor) Grošelj, Uroš (Avtor) organocatalysisasymmetric synthesisenantioselectivitysolvent effectspyrrolonepseudo-enantiomeric catalyst conformationsArylidene-Δ2-pyrrolin-4-ones undergo organocatalyzed annulation with malononitrile, furnishing dihydropyrano[3,2-b]pyrroles (18 examples, 0–77% ee in dichloromethane, 11–44% ee in methanol). The products could be enantiomerically enriched by trituration (11 examples, 95–99% ee). Enantioselectivity was dependent on the nature of the substrate and the conformation of the catalyst, which in turn was solvent-controlled. The reaction mechanism, which included two pseudo-enantiomeric organocatalyst conformations, was investigated by experimental and quantum chemical methods. The reaction mechanism consists of Michael addition reaction step followed by 6-exo-dig annulation, which was found to be the rate determining step. Additionally, it was identified that the preferred reaction pathway follows the model originally proposed by Pápai et al.20222022-02-15 12:35:54Članek v reviji134970UDK: 547.74:544.47ISSN pri članku: 1615-4150DOI: 10.1002/adsc.202101369COBISS_ID: 97278211sl