TY  - JOUR
A1  - Behrendt, Felix Nicolas
A1  - Schlaad, Helmut
T1  - Entropy-Driven Ring-Opening Disulfide Metathesis Polymerization for the Synthesis of Functional Poly(disulfide)s
JF  - Macromolecular rapid communications
N2  - Metal-free entropy-driven disulfide metathesis polymerization of unsaturated L-cystine based macrocycles produces high-molar-mass heterofunctional poly(disulfide)s, i.e., poly(ester-disulfide-alkene) and poly(amide-disulfide-alkene); M-w(app) = 44-60 kDa, (sic) > 1.7. The polymerization is fast and reaches equilibrium within 1-5 minutes (monomer conversion 70-90%) in polar aprotic solvents such as N,N-dimethylacetamide, dimethylsulfoxide, or y-valerolactone. Thiol-terminated polymers are stable in bulk or when dissolved in weakly polar solvents, but rapidly depolymerize in dilute polar solution.
KW  - disulfide
KW  - macrocycles
KW  - metathesis
KW  - ring-opening polymerization
Y1  - 2018
U6  - https://doi.org/10.1002/marc.201700735
SN  - 1022-1336
SN  - 1521-3927
VL  - 39
IS  - 6
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Karras, Manfred
A1  - Dabrowski, Michal
A1  - Pohl, Radek
A1  - Rybacek, Jiri
A1  - Vacek, Jaroslav
A1  - Bednarova, Lucie
A1  - Grela, Karol
A1  - Stary, Ivo
A1  - Stara, Irena G.
A1  - Schmidt, Bernd
T1  - Helicenes as Chirality-Inducing Groups in Transition-Metal Catalysis
BT  - the first helically chiral Olefin Metathesis Catalyst
JF  - Chemistry - a European journal
N2  - 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.
KW  - asymmetric catalysis
KW  - carbene ligands
KW  - helicenes
KW  - metathesis
KW  - ruthenium
Y1  - 2018
U6  - https://doi.org/10.1002/chem.201802786
SN  - 0947-6539
SN  - 1521-3765
VL  - 24
IS  - 43
SP  - 10994
EP  - 10998
PB  - Wiley-VCH
CY  - Weinheim
ER  -