Isotopic exchanges in the treatment of cyclopentane or cyclohexane with some deuterated or tritiated acids

Abstract

The exchange between the H atoms of cyclopentane (3) or cyclohexane (4) and the labeled acid protons of CF3SO3D (2-d), [3H]CF3SO3H (2-t), [3H]H2SO4 (1-t), or ZnCl2−[3H]HCl (5-t) has been investigated. Results from the treatment of 3 or 4 with 2-d at 0° or 20 °C, respectively, gave rise to polydeuterated cycloalkanes, indicating that all H atoms of 3 or 4 could be involved in the exchange. The rates of incorporation of the T-label into the hydrocarbon layer from the tritiated acids were found to be directly related to acid strength. After treatment of 3 or 4 with 2-t, quenching of the acid layer and analysis by isotope dilution showed the presence of cyclopentanol or cyclohexanol. A carbocationic chain mechanism for the exchange, as well as the mechanism for the formation of the cycloalkyl cation from the cycloalkane, are discussed.

Exploring Superacid‐Promoted Skeletal Reorganization of Aliphatic Nitrogen‐Containing Compounds

“…The same product 5 a was obtained in 97 % yield by reacting 2 a under similar conditions, indicating that 2 a must be in equilibrium with an acyclic cationic intermediate in superacid solution (Figure 2c). [18] To gain more information about the transfer of the isopropyl moiety along the reaction, substrate 1a D was prepared and submitted to superacid conditions (Figure 2d). The reaction led to the unique formation of a 2a D exhibiting 0.5 D incorporation in position 4, suggesting that an electron‐deficient center may be developed in this position at an intermediate stage of the reaction which is then reduced by hydride transfer coming from the isopropyl moiety.…”