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Molecules 2018, 23(2), 438; https://doi.org/10.3390/molecules23020438

Asymmetric Synthesis of Spirooxindoles via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts

1
Dipartimento di Scienze- Sezione di Nanoscienze e Nanotecnologie, Università degli Studi di Roma Tre, V.le G. Marconi 446, I-00146 Rome, Italy
2
Dipartimento di Medicina Molecolare e Traslazionale (DMMT), Università di Brescia, viale Europa 11, 25123 Brescia, Italy
3
Dipartimento di Scienze, Università degli Studi della Basilicata, via dell′Ateneo Lucano 10, I-85100 Potenza, Italy
*
Author to whom correspondence should be addressed.
Received: 5 February 2018 / Revised: 12 February 2018 / Accepted: 12 February 2018 / Published: 16 February 2018
(This article belongs to the Special Issue Enantioselective Catalysis)
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Abstract

Taking into account the postulated reaction mechanism for the organocatalytic epoxidation of electron-poor olefins developed by our laboratory, we have investigated the key factors able to positively influence the H-bond network installed inside the substrate/catalyst/oxidizing agent. With this aim, we have: (i) tested a few catalysts displaying various effects that noticeably differ in terms of steric hindrance and electron demand; (ii) employed α-alkylidene oxindoles decorated with different substituents on the aromatic ring (11ag), the exocylic double bond (11hl), and the amide moiety (11mv). The observed results suggest that the modification of the electron-withdrawing group (EWG) weakly conditions the overall outcomes, and conversely a strong influence is unambiguously ascribable to either the N-protected or N-unprotected lactam framework. Specifically, when the NH free substrates (11mu) are employed, an inversion of the stereochemical control is observed, while the introduction of a Boc protecting group affords the desired product 12v in excellent enantioselectivity (97:3 er). View Full-Text
Keywords: epoxidation; organocatalysis; epoxyoxindole; alkylidenoxindoles; H-bond network; non-covalent catalysis; chiroptical properties epoxidation; organocatalysis; epoxyoxindole; alkylidenoxindoles; H-bond network; non-covalent catalysis; chiroptical properties
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Miceli, M.; Mazziotta, A.; Palumbo, C.; Roma, E.; Tosi, E.; Longhi, G.; Abbate, S.; Lupattelli, P.; Mazzeo, G.; Gasperi, T. Asymmetric Synthesis of Spirooxindoles via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts. Molecules 2018, 23, 438.

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