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Improved stereoselectivity has been obtained by using 2-lithium-1-methylimidazole, 2, as a replacement for lithium diisopropylamide (LDA) as a bulk base in catalytic deprotonations. The chiral lithium amide 6 of (1R,2S)-N-methyl-1-phenyl-2-pyrrolidinylpropanamine, 5, has been found to deprotonate cyclohexene oxide 3 in the presence of compound 2 to yield (S)-cyclohex-2-en-1-ol, 4, in 96% ee. Compound 2 is a carbenoid species conveniently generated from nBuLi and 1-methylimidazole, 1. The base 2 has also been found to play a more intimate role in the deprotonation. Investigations by 1H, 6Li and 13C NMR of the 6Li/15N isotopologue 8 of 6 have shown that 6 is homodimeric in THF and that, in the presence of 2, it forms a novel heterodimer 10. This heterodimer is found to be the dominant reagent in the initial state, rather than the homodimer of 6. Computational investigations with PM3 and B3LYP/6-311 + G(d,p) have shown possible structures of the heterodimers, as well as the role of THF and I in the solvation of the dimers. The results are in line with the NMR results. Favoured complexes in the equilibria between homo- and heterocomplexes are also reported.

The transition states for methane activation in liquid superacid have been studied by experimentally determined secondary kinetic deuterium isotope effects (SKIEs) and computational chemistry. For the first time, the SKIEs on hydrogen/deuterium exchange of methane have been measured by using the methane isotopologues in homogeneous liquid superacid (2HF/SbF5). To achieve high accuracy of the SKIEs, the rate constants for pairs of methane isotopologues were simultaneously measured in the same superacid solution by using NMR spectroscopy. Density functional theory (DFT) and high-level ab initio methods have been employed to model possible intermediates and transition states, assuming that the superacids involved in the exchange reactions are H2F+ ions solvated by HF. Only the unsolvated superacid H2F+ is found to be strong enough to protonate methane, yielding the methonium ion solvated by HF as a potential energy minimum. In contrast, the (HF)x-solvated H2F+ superacids (x = 1-4) do not appear to be strong enough to yield stable solvated methonium ions. However, such ions show up as parts of the transition states of the exchange in which the methonium ions are solvated by (HF)x. The calculated DFT activation barrier is in good agreement with that experimentally observed.