Conformationally restricted dynamic supramolecular catalysts for substrate-selective epoxidations
作者:Esmaeil Sheibani、Kenneth Wärnmark
DOI:10.1039/c2ob06859a
日期:——
A second generation of a substrate-selective dynamic supramolecular catalytic system consisting of a catalyst part and a receptor part, connected by a hydrogen-bonding motif, has been realized based on rational design. The results from analyses of the equilibrium mixture of the species generated by the components of the first generation system led us to selectively lock the cisoid conformation of the catalyst part to increase the amount of the substrate-selective catalytic cavity in the equilibrium mixture. This was realized by strapping the catalyst part by organic synthesis. This strapping led to an increase in substrate selectivity in the pair-wise competitive epoxidations of pyridyl- vs. phenyl-appended styrenes and pyridyl- vs. phenyl-appended stilbenes of both Z- and E- configuration compared to the first generation system, reaching 3.4 : 1 as the highest substrate selectivity for Z-mono-pyridyl-stilbene (27a) vs. the corresponding all-carbon analogue (28a) and for E-dipyridyl-stilbene (26b) vs. the corresponding all-carbon analogue (28b), respectively.
Modulation of the reactivity, stability and substrate- and enantioselectivity of an epoxidation catalyst by noncovalent dynamic attachment of a receptor functionality—aspects on the mechanism of the Jacobsen–Katsuki epoxidation applied to a supramolecular system
作者:Stefán Jónsson、Fabrice G. J. Odille、Per-Ola Norrby、Kenneth Wärnmark
DOI:10.1039/b518244a
日期:——
The synthesis of the components of the dynamic supramolecular hydrogen-bonded catalytic system 2 + 3 is described. The catalytic performance and substrate- and enantioselectivity of Mn(salen) catalyst 2 were investigated in the presence and absence of the Zn(porphyrin) receptor unit 3. The effects of pyridine and pyridine N-oxide donor ligands were also studied. Some aspects on the mechanism of the
A dynamic supramolecular system exhibiting substrate selectivity in the catalytic epoxidation of olefins
作者:Stefán Jónsson、Fabrice G. J. Odille、Per-Ola Norrby、Kenneth Wärnmark
DOI:10.1039/b411978a
日期:——
A dynamic supramolecular system involving hydrogen bonding between a Mn(III) salen catalyst and a Zn(II) porphyrin receptor exhibitsselectivity for pyridine appended cis-beta-substituted styrene derivatives over phenyl appended derivatives in a catalytic epoxidation reaction.