Effect of the nO → π*C═O Interaction on the Conformational Preference of 1,3-Diketones: A Case Study of Riolozatrione Derivatives

Autor: Ramiro F. Quijano-Quiñones, Rubén A. Toscano, Beatriz Quiroz-García, Gabriel Cuevas, Tannya R. Ibarra-Rivera, Juan F. Tamez-Fernández, Diego Martínez-Otero, José Enrique Barquera-Lozada, Fabián Cuétara-Guadarrama, Fatima M. Soto-Suárez, Karla Ramírez-Gualito, Yolanda D. Estrada-Chavarría, Verónica M. Rivas-Galindo, Víctor Duarte-Alaniz
Rok vydání: 2021
Předmět:
Zdroj: The Journal of Organic Chemistry. 86:9540-9551
ISSN: 1520-6904
0022-3263
Popis: 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.
Databáze: OpenAIRE
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