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Anion–π Catalysis on Carbon Nanotubes
Author(s) -
Bornhof AnnaBea,
VázquezNakagawa Mikiko,
RodríguezPérez Laura,
Ángeles Herranz María,
Sakai Naomi,
Martín Nazario,
Matile Stefan,
LópezAndarias Javier
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201909540
Subject(s) - catalysis , carbon nanotube , polarizability , chemistry , synergistic catalysis , ion , photochemistry , homogeneous catalysis , inorganic chemistry , nanotechnology , materials science , organic chemistry , molecule
Abstract Induced π acidity from polarizability is emerging as the most effective way to stabilize anionic transition states on aromatic π surfaces, that is, anion–π catalysis. To access extreme polarizability, we propose a shift from homogeneous toward heterogeneous anion–π catalysis on higher carbon allotropes. According to benchmark enolate addition chemistry, multi‐walled carbon nanotubes equipped with tertiary amine bases outperform single‐walled carbon nanotubes. This is consistent with the polarizability of the former not only along but also between the tubes. Inactivation by π‐basic aromatics and saturation with increasing catalyst concentration support that catalysis occurs on the π surface of the tubes. Increasing rate and selectivity of existing anion–π catalysts on the surface of unmodified nanotubes is consistent with transition‐state stabilization by electron sharing into the tubes, i.e., induced anion–π interactions. On pristine tubes, anion–π catalysis is realized by non‐covalent interfacing with π‐basic pyrenes.