Preparation, ¹³C NMR and IGLO/DFT Studies of Trifluoromethyl Substituted Allyl Cations

Author

George Andrew Olah
Prakash Reddy, Missouri University of Science and TechnologyFollow
Joseph Casanova
G. K. Surya Prakash

Abstract

2-(Adamantylidenemethyl)-2-adamantyl cation (5) was prepared by ionization of 2-(adamantylidenemethyl)-2-adlamantanol (9) in FSO₃H/SO₂ClF or neat FSO₃H at -78°C. In spite of its high inherent steric strain, carbocation 5 is stable up to 80°C. Its rotational barrier was estimated to be 16.8 kcal/mol on the basis of the coalescence temperature of the ¹³C NMR signals of its diastereomeric ß-methylene carbons, which is in agreement with a ΔH^‡ value of 16.5 kcal/mol calculated by MNDO. Similarly, 2-adamantylidene-1,1-dicyclopropylethyl cation (6) was prepared by the ionization of 1,1-dicyclopropyl-2-(2-hydroxy-2-adamantyl)ethanol (12) in SbF₅-FSO/SO₂ClF or FSO₃H/SO₂ClF. Carbocation 6 shows a rotational barrier of less than 5 kcal/mol. The small rotational barrier in 6 is interpreted as due to the positive charge stabilizing influence of the adjacent cyclopropyl groups resulting in an unsymmetrically charge-delocalized allylic cation.

Recommended Citation

G. A. Olah et al., "Preparation, ¹³C NMR and IGLO/DFT Studies of Trifluoromethyl Substituted Allyl Cations," Journal of Organic Chemistry, vol. 57, no. 24, pp. 6431 - 6434, American Chemical Society (ACS), Nov 1992.

The definitive version is available at https://doi.org/10.1021/jo00050a014

Department(s)

Chemistry

International Standard Serial Number (ISSN)

0022-3263

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1992 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Nov 1992