Reaction of 1-methylpyrazole with n-BuLi in THF followed by reaction with monodeuteromethanol (CH3OD) under kinetically controlled conditions leads to functionalisation at the methyl group, whereas reaction under thermodynamically controlled conditions leads to functionalisation at the pyrazole 5-position. The observed regioselectivity can be correctly predicted, at least qualitatively, using density functional B3LYP/6-31+G(d,p) calculations only when solvation effects (IEFPCM) are taken into account. The 1H,6Li HOESY and NOESY NMR spectra of the thermodynamic product 5-lithio-1-methylpyrazole (5-Li) in [D8]THF are consistent with an oligomeric structure.
1-甲基吡唑在
四氢呋喃中与
正丁基锂反应,然后在动力学控制条件下与单
氘代甲醇(CH3OD)反应,导致甲基官能化;而在热力学控制条件下反应,则导致
吡唑5位官能化。只有考虑溶剂效应(IEFPCM),才能使用密度泛函B3LYP/6-31+G(d,p)计算正确预测(至少是定性预测)所观察到的区域选择性。在[D8]THF中,热力学产物5-
锂-
1-甲基吡唑(5-Li)的1H,6Li HOESY和NOESY NMR光谱与低聚物结构一致。