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Highly Active and Robust Metalloporphyrin Catalysts for the Synthesis of Cyclic Carbonates from a Broad Range of Epoxides and Carbon Dioxide
Author(s) -
Maeda Chihiro,
Shimonishi Junta,
Miyazaki Ray,
Hasegawa Junya,
Ema Tadashi
Publication year - 2016
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.201600164
Subject(s) - catalysis , nucleophile , chemistry , epoxide , carbon dioxide , porphyrin , solvent , nitro , reactivity (psychology) , bifunctional , turnover number , organic chemistry , inorganic chemistry , alkyl , medicine , alternative medicine , pathology
Bifunctional metalloporphyrins with quaternary ammonium bromides (nucleophiles) at the meta , para , or ortho positions of meso ‐phenyl groups were synthesized as catalysts for the formation of cyclic carbonates from epoxides and carbon dioxide under solvent‐free conditions. The meta ‐substituted catalysts exhibited high catalytic performance, whereas the para ‐ and ortho ‐substituted catalysts showed moderate and low activity, respectively. DFT calculations revealed the origin of the advantage of the meta ‐substituted catalyst, which could use the flexible quaternary ammonium cation at the meta position to stabilize various anionic species generated during catalysis. A zinc(II) porphyrin with eight nucleophiles at the meta positions showed very high catalytic activity (turnover number (TON)=240 000 at 120 °C, turnover frequency (TOF)=31 500 h −1 at 170 °C) at an initial CO 2 pressure of 1.7 MPa; catalyzed the reaction even at atmospheric CO 2 pressure (balloon) at ambient temperature (20 °C); and was applicable to a broad range of substrates, including terminal and internal epoxides.