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Guanidines: Highly Nucleophilic Organocatalysts
Author(s) -
Maji Biplab,
Stephenson David S.,
Mayr Herbert
Publication year - 2012
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201200143
Subject(s) - nucleophile , chemistry , pyridine , reaction rate constant , michael reaction , organocatalysis , medicinal chemistry , catalysis , organic chemistry , kinetics , enantioselective synthesis , physics , quantum mechanics
The nucleophile‐specific parameters N and s N , as defined by log k 20 °C = s N ( N + E ) have been derived for the guanidines 1 a – h from the second‐order rate constants of their reactions with diarylcarbenium tetrafluoroborates in CH 2 Cl 2 at 20 °C. The applicability of these parameters for predicting rate constants of the reactions of guanidines with ordinary Michael acceptors has been demonstrated. Comparison with other organocatalysts shows that 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene, the strongest nucleophile of this series, exceeds the nucleophilicity of diazabicyclononene and 4‐(dimethylamino)pyridine by factors of 3 to 7.
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