Electrophilic aromatic substitutions of aryltrifluoroborates with retention of the BF3- group: Quantification of the activating and directing effects of the trifluoroborate group

Guillaume Berionni, Varvara Morozova, Maximilian Heininger, Peter Mayer, Paul Knochel, Herbert Mayr

Résultats de recherche: Contribution à un journal/une revueArticleRevue par des pairs

Résumé

Kinetics and mechanisms of transition-metal free reactions of furyl, thienyl and indolyl trifluoroborates with benzhydrylium (Ar2CH +) and iminium (Me2N+=CHR) ions have been investigated. In contrast to common belief, substitutions at CH positions are often faster than ipso-substitutions of the BF3K group, because BF3K activates the position attached to boron by a factor of 10 3-104 while adjacent CH positions are activated by factors of 105-106. Several reactions that have previously been interpreted as ipso-substitutions actually proceed via initial substitution at a vicinal or remote CH position, followed by protodeborylation. If the proton released during electrophilic substitution at a CH position is trapped by a base, the BF3- group can be preserved. Remote reactions of heteroaryl trifluoroborates with iminium ions provide straightforward access to novel zwitterionic ammonium or iminium trifluoroborates, which have been characterized by single-crystal X-ray analyses.

langue originaleAnglais
Pages (de - à)6317-6324
Nombre de pages8
journalJournal of the American Chemical Society
Volume135
Numéro de publication16
Les DOIs
Etat de la publicationPublié - 24 avr. 2013
Modification externeOui

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