The reactivity of groups lying in close proximity of a crown-ether moiety where a metal ion is hosted, has been investigated in model systems. We have found that methyl transfer and acyl transfer reactions are greatly accelerated by alkali and alkaline-earth metal ions. Rate enhancements in the order of 10^2-10^3 are commonly observed, but exceptionally high values in the order of 10^5-10^7 are also found in some cases, which correspond to transition state stabilizations of some 7-10 kcal/mol.
SPECIFIC TRANSITION-STATE STABILIZATION BY METAL-IONS IN REACTIONS OF FUNCTIONALIZED CROWN ETHERS
CACCIAPAGLIA R;MANDOLINI L
1993
Abstract
The reactivity of groups lying in close proximity of a crown-ether moiety where a metal ion is hosted, has been investigated in model systems. We have found that methyl transfer and acyl transfer reactions are greatly accelerated by alkali and alkaline-earth metal ions. Rate enhancements in the order of 10^2-10^3 are commonly observed, but exceptionally high values in the order of 10^5-10^7 are also found in some cases, which correspond to transition state stabilizations of some 7-10 kcal/mol.File in questo prodotto:
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