Effect of the nO → πCO Interaction on the Conformational Preference of 1,3-Diketones: A Case Study of Riolozatrione Derivatives

The cyclopropane ring-opening reaction of riolozatrione, a natural product obtained from Jatropha dioica, afforded a 2,2-disubstituted 1,3-cyclohexandione displaying an alkyl methyl ether group at position 5. The conformational analysis of this product showed a high preference for the trans-diaxial...

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Published in:Journal of organic chemistry 2021-07, Vol.86 (14), p.9540-9551
Main Authors: Tamez-Fernández, Juan F, Soto-Suárez, Fátima M, Estrada-Chavarría, Yolanda D, Quijano-Quiñones, Ramiro F, Toscano, Rubén A, Cuétara-Guadarrama, Fabián, Duarte-Alaniz, Víctor, Ibarra-Rivera, Tannya R, Quiroz-García, Beatriz, Martínez-Otero, Diego, Ramírez-Gualito, Karla, Barquera-Lozada, José Enrique, Rivas-Galindo, Verónica M, Cuevas, Gabriel
Format: Article
Language:English
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Summary:The cyclopropane ring-opening reaction of riolozatrione, a natural product obtained from Jatropha dioica, afforded a 2,2-disubstituted 1,3-cyclohexandione displaying an alkyl methyl ether group at position 5. The conformational analysis of this product showed a high preference for the trans-diaxial conformation in both solution and solid state. Such conformation was possible from the noncovalent intramolecular nX → π*CO interactions (X = an element having an unshared electron pair), allowing the determination of the interaction energies. Since the nX → π*CO interactions can be regarded as additive, the energy values ranged from 4.52 to 6.51 kcal mol–1 for each carbonyl group with a strong dependency on the interatomic distances. The rigorous analysis of the electron density in the topological theory of atoms in molecules framework clearly shows that the origin of O–CO interactions are through the nO → π*CO electron transfer mechanism. Such interactions are slightly weaker than a canonical hydrogen bond but seemingly stronger than a van der Waals interaction. This interaction must be considered as a stereoelectronic effect due the electronic transfer between the interacting groups, which are limited by their relative stereochemistry and can be represented by a bond–no bond interaction, causing the pyramidalization of the carbonyl, which is the charge acceptor group.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.1c00847