Lithium diisopropylamide-mediated enolizations: Solvent-independent rates. solvent-dependent mechanisms

被引：75

作者：

Sun, XF ^{[1
]}

Collum, DB ^{[1
]}

机构：

[1] Cornell Univ, Baker Lab, Dept Chem & Chem Biol, Ithaca, NY 14853 USA

来源：

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | 2000年 / 122卷 / 11期

关键词：

D O I：

10.1021/ja992062z

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

Rate studies of a lithium diisopropylamide-mediated ester enolization reveal solvation effects that are not in accord with expectation. Metalations in THF, t-BuOMe, HMPA/THF, and DMPU/THF (HMPA = hexamethylphosphoramide, DMPU = 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidone) occur at nearly the same rates, yet proceed via four fundamentally distinct scenarios: (1) disolvated monomer in THF, (2) monosolvated dimer in t-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 t-BuOMe and triple ions in HMPA/THF underscores the importance of aggregate-based reactions.

引用

页码：2452 / 2458

页数：7

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