Solvent and Stereoelectronic Effects on the Solvolysis Rates of Oxaspirocyclopropanated 1-Norbornyl Triflates and Related Bridgehead Derivatives

• Published in: Journal of organic chemistry Vol. 73; no. 17; pp. 6607 - 6614
• Main Authors: García Martínez, Antonio, de la Moya Cerero, Santiago, Teso Vilar, Enrique, García Fraile, Amelia, Lora Maroto, Beatriz, Díaz Morillo, Cristina
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 05.09.2008; Amer Chemical Soc
• Subjects: Alicyclic compounds; Alicyclic compounds, terpenoids, prostaglandins, steroids; Chemistry; Chemistry, Organic; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Physical Sciences; Preparations and properties; Reactivity and mechanisms; Science & Technology; TERTIARY CARBENIUM IONS; CARBOCATIONS; BICYCLO<1.1.1>PENTANE; STABILITY; GAS-PHASE; REACTIVITY; PRINCIPLE; ENERGIES; MOLECULAR-MECHANICS; CATIONS; Solvent effect; Chemical solution; Chemical rearrangement; Correlation; Cyclopropane derivatives; Theoretical study; Solvolysis; Stereochemistry; Experimental study; Reaction rate; Free energy; Spiran; Fragmentation; Solvation; Steric effect; Ionization; Carbocation; Density functional method; Electronic effect; Kinetics; Gas phase; Solvent
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo8009787

The study of the stereochemical outcome of the solvolysis of oxaspirocyclopropanated 1-norbornyl triflates is highly interesting since these reactions do not lead to the usual retention or fragmentation products but only synthetically interesting rearranged products are enantiospecifically formed. There is no correlation between the experimental solvolysis rates (ln k) and the B3LYP/6-31G(d)-computed ionization energies (ΔE) of the corresponding bridgehead hydrocarbons in gas phase. However, this work demonstrates the existence of a fair linear correlation between the experimental reaction rates and the PCM//B3LYP/6-31G(d)-computed free ionization energies in solution (ΔG). This theoretically relevant result reveals that the reason for the lack of linearity in gas phase is not the rearrangement of the intermediate carbocations but unspecific solvent effects on the solvolysis rates, accounted for by the PCM model.