Volume 7, Issue 2 p. 291-296
Full Paper

Supramolecular Encapsulation of Neutral Diazoacetate Esters and Catalyzed 1,3-Dipolar Cycloaddition Reaction by a Self-Assembled Hexameric Capsule

Giorgio La Sorella

Giorgio La Sorella

Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Calle Larga S. Marta 2137, 30123, Venezia (Italy), Fax: (+39) 0412348517

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Laura Sperni

Laura Sperni

Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Calle Larga S. Marta 2137, 30123, Venezia (Italy), Fax: (+39) 0412348517

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Prof. Dr. Giorgio Strukul

Prof. Dr. Giorgio Strukul

Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Calle Larga S. Marta 2137, 30123, Venezia (Italy), Fax: (+39) 0412348517

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Dr. Alessandro Scarso

Corresponding Author

Dr. Alessandro Scarso

Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Calle Larga S. Marta 2137, 30123, Venezia (Italy), Fax: (+39) 0412348517

Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Calle Larga S. Marta 2137, 30123, Venezia (Italy), Fax: (+39) 0412348517Search for more papers by this author
First published: 12 December 2014
Citations: 35

Graphical Abstract

Stuck in the middle: Diazoacetate esters are suitable neutral guests for the self-assembled resorcin[4]arene hexameric capsule. The hydrogen-bonded supramolecular host efficiently catalyzes 1,3-dipolar cycloadditions between such substrates and electron-poor alkenes, which leads to 4,5-dihydro-1H-pyrazole derivatives. The presence of competitive cationic guests for the capsule confirms that the reaction occurs within the cavity.

Abstract

Diazoacetate esters proved to be suitable neutral guests for the self-assembled resorcin[4]arene hexameric capsule. The hydrogen-bonded supramolecular host catalyzed the 1,3-dipolar cycloaddition reaction between diazoacetate esters and electron-poor alkenes such as acrolein, acrylonitrile, predominantly trans-crotonaldehyde, trans-2-hexenal, methyl, and butyl acrylate, which led to the corresponding 4,5-dihydro-1H-pyrazole derivatives. The cycloaddition reaction occurred within the cavity of the capsule. In fact, substantial inhibition of the catalytic activity was observed by employing tetraethylammonium tetrafluoroborate characterized by greater affinity for the hexameric capsule as a competitive guest; its presence inhibited access of the substrates. The 1,3-dipolar cycloaddition reaction between diazoacetate esters and acrylate esters of different lengths showed a significant degree of substrate selectivity owing to the encapsulation of the reagents before the cycloaddition reaction.