10.1021/ja992062z.s001 Xiufeng Sun Xiufeng Sun David B. Collum David B. Collum Lithium Diisopropylamide-Mediated Enolizations:  Solvent-Independent Rates, Solvent-Dependent Mechanisms American Chemical Society 2000 HMPA BuOMe DMPU disolvated monomers monosolvated monomer THF solvation effects tetrasolvated dimer 2000-03-02 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Lithium_Diisopropylamide-Mediated_Enolizations_Solvent-Independent_Rates_Solvent-Dependent_Mechanisms/3676059 Rate studies of a lithium diisopropylamide-mediated ester enolization reveal solvation effects that are not in accord with expectation. Metalations in THF, <i>t</i>-BuOMe, HMPA/THF, and DMPU/THF (HMPA = hexamethylphosphoramide, DMPU = 1,3-dimethyl-3,4,5,6-tetrahydro-2(1<i>H</i>)-pyrimidone) occur at nearly the same rates, yet proceed via four fundamentally distinct scenarios:  (1) disolvated monomer in THF, (2) monosolvated dimer in <i>t</i>-BuOMe, (3) both monosolvated monomer and tetrasolvated dimer in HMPA/THF, and (4) mono- and disolvated monomers in DMPU/THF. The implication of reactive open dimers in <i>t</i>-BuOMe and triple ions in HMPA/THF underscores the importance of aggregate-based reactions.