| Sumario: | The remarkable accelerating effect of 1,2,3- triazolyl substituents on SNAr reactions has been investigated through systematic experiments and density functional theory calculations. The lone pair electrons of an orfho-triazolo substituent play a key role in lowering the activation energy for nucleophilic addition via formation of a preferential hydrogen bond with the amine nucleophile at the transition state for addition. In an extension of this finding, a series of related heteroaryl groups with similar electron pair donor properties have also been found to facilitate SNAr reactions. The experimentally determined solvent effect provides further support for this rationale, which was utilized to achieve an ortho-selective substitution on a difluoroarene substrate.
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