The stability of cyclopropyllithium in diethyl ether and in tetrahydrofuran

Cyclopropyllithium aggaregation and199Hg NMR as a tool for exchange studies with organo‐mercury compounds

“…For a ca. 0.1 M solution of 1 in [D 10 ]DEE, we found at 173 K a singlet in the 1 H-decoupled 6 Li NMR spectrum close to the external reference of LiBr/THF (± 0.2 ppm). At the same temperature, the 13 C{ 1 H} spectrum shows at δ −9.64 a septuplet for the resonance of the lithiated carbon with a coupling of 6.5 ± 0.2 Hz ( Figure 1A) and an experimental intensity distribution given in Table 1.…”

“…2.1 | The solution structure of the parent compound 1 in DEE and in THF Salt-free 1 was synthesized from cyclopropylmercury [18] by metal exchange with 6 Li powder. For a ca.…”

“…[5] The unusual stability of 1 in ethereal solvents was already noted by Seyferth and Cohen, [6] and its reactivity was found to be comparable rather to vinyllithium than to other alkyllithium compounds. Only in the case of triphenylphosphonium cyclopropylid [7] and for systems with phenylsubstitution at C-1, [8] that can also be regarded as benzyllithium derivatives, was experimental evidence for an inversion process at the metalated carbon reported.…”

“…Several theoretical studies addressed the influence of † This article is published as part of a special issue to celebrate the 80 th birthday of Professor Waldemar Adam NMR-Spectroscopy of Organolithium Compounds, Part XXXII; for Part XXXI see [3] metalation on the structure of the 3-membered ring [9,10] and the 1 H and 13 C NMR spectra of 1 were analyzed in detail. [6,11,12] Lagow was able to synthesize even a cyclopropane derivative with two geminal lithium atoms. [13] Later, in their pioneering work on carbonlithium NMR coupling constants, Seebach, Hässig and Gabriel [14] described dimer formation for 2-phenylcyclopropyllithium, 7-lithionorcaran, and bicyclobutyllithium in THF.…”

“…In connection with structural work on the aggregation behavior of mono-and dilithiated organolithium compounds, [16] we felt that a closer look on the solution structure of 1 and some of its methyl derivatives, trans-2,3-dimethyl-1 (2) and 2,2,3,3-tetramethyl-1 (3), using various NMR techniques and samples enriched with the NMR-friendly isotope 6 Li [17] would be rewarding.…”