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Structure–Nucleophilicity Relationships for Enamines
Author(s) -
Kempf Bernhard,
Hampel Nathalie,
Ofial Armin R.,
Mayr Herbert
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200204666
Subject(s) - ketene , chemistry , nucleophile , carbanion , reactivity (psychology) , silylation , iminium , enol , reaction rate constant , dichloromethane , medicinal chemistry , computational chemistry , double bond , photochemistry , organic chemistry , kinetics , ion , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics , solvent
The kinetics of the reactions of benzhydryl cations with 22 enamines, three pyrroles, and three indoles were investigated photometrically in dichloromethane. The nucleophilicity parameters N and slope parameters s of these electron‐rich π‐systems were derived from equation log k (20 °C)= s ( E + N ) and compared with the nucleophilicities of other π‐systems (silyl enol ethers, silyl ketene acetals) and carbanions. It is shown that the nucleophilic reactivities of enamines cover more than ten orders of magnitude, comparable to enol ethers on the low reactivity end and to carbanions on the high reactivity end. Since the products of Nattack are thermodynamically less stable than the reactants, the observed rate constants refer to the formation of the carbon carbon bonds. In some cases, equilibrium constants for the formation of iminium ions were measured, which allow one to determine the intrinsic rate constants of these reactions.