A hexameric resorcinarene capsule acts as a hydrogen bonding catalyst for the activation of encapsulated nitroalkenes toward the addition of pyrroles and indoles. Once inside the capsule (C), β-nitrostyrene 3a establishes H-bonding interactions with the bridging water molecules having free H-bond-donating valences. Thus, the activation of nitroalkenes favors the conjugate addition of pyrroles and indoles. It is demonstrated that the inherent acidity of capsule C is sufficient to promote the Michael-type Friedel–Crafts (MTFC) reaction under the mild reaction conditions described herein. In silico calculations point out the catalytically relevant role of the bridging water molecules of C and confirm the supramolecular control exerted by the capsule, which protects the nitronic acid intermediate with respect to the degradation pathway that commonly occurs in the bulk medium.
A hexameric resorcinarene capsule as a hydrogen bonding catalyst in the conjugate addition of pyrroles and indoles to nitroalkenes
Gambaro, Stefania;De Rosa, Margherita
;Soriente, Annunziata;Talotta, Carmen;Gaeta, Carmine;Neri, Placido
2019-01-01
Abstract
A hexameric resorcinarene capsule acts as a hydrogen bonding catalyst for the activation of encapsulated nitroalkenes toward the addition of pyrroles and indoles. Once inside the capsule (C), β-nitrostyrene 3a establishes H-bonding interactions with the bridging water molecules having free H-bond-donating valences. Thus, the activation of nitroalkenes favors the conjugate addition of pyrroles and indoles. It is demonstrated that the inherent acidity of capsule C is sufficient to promote the Michael-type Friedel–Crafts (MTFC) reaction under the mild reaction conditions described herein. In silico calculations point out the catalytically relevant role of the bridging water molecules of C and confirm the supramolecular control exerted by the capsule, which protects the nitronic acid intermediate with respect to the degradation pathway that commonly occurs in the bulk medium.File | Dimensione | Formato | |
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The Hexameric Resorcinarene Capsule as a Hydrogen Bonding Catalyst in the Conjugate Addition of Pyrroles and Indoles to Nitroalkenes _accepted version.pdf
Open Access dal 02/05/2020
Descrizione: Manuscript _accepted version
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