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Helicenes as Chirality‐Inducing Groups in Transition‐Metal Catalysis: The First Helically Chiral Olefin Metathesis Catalyst
Author(s) -
Karras Manfred,
Dąbrowski Michał,
Pohl Radek,
Rybáček Jiří,
Vacek Jaroslav,
Bednárová Lucie,
Grela Karol,
Starý Ivo,
Stará Irena G.,
Schmidt Bernd
Publication year - 2018
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.201802786
Subject(s) - metathesis , chirality (physics) , catalysis , olefin metathesis , salt metathesis reaction , ring opening metathesis polymerisation , ring closing metathesis , enantioselective synthesis , steric effects , chemistry , stereochemistry , materials science , organic chemistry , polymerization , physics , chiral symmetry breaking , symmetry breaking , nambu–jona lasinio model , polymer , quantum mechanics
Helical chirality is a novel enantioselectivity‐inducing property in transition‐metal‐catalyzed transformations. The principle is illustrated herein for the example of asymmetric olefin metathesis. This work reports the synthesis of the first helically chiral Ru‐NHC alkylidene complex from an aminohelicene‐derived imidazolium salt, which was ligated to the first generation Hoveyda–Grubbs catalyst. Kinetic data were acquired for benchmark test reactions and compared to an achiral catalyst. The helically chiral Ru‐catalyst was evaluated in asymmetric ring‐closing metathesis (RCM) and ring‐opening metathesis–cross‐metathesis (ROM/CM) reactions, which proceeded with promising levels of enantioselectivity. Extensive NMR‐spectroscopic investigations and a DFT geometry optimization were performed. These results led to a topographic steric map and calculation of percent‐buried‐volume values for each quadrant around the metal center.