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Relevant academic research and scientific papers

A Unique Binaphthyl Strapped Iron-Porphyrin Catalyst for the Enantioselective Epoxidation of Terminal Olefins

A new chiral binaphthyl-strapped iron-porphyrin 4b that exhibits unprecedented catalytic activity toward the enantioselective epoxidation of terminal olefins was synthesized. Typical enantiomeric excesses (ee) of 90% were measured with a maximum of 97% fo

Asymmetric Epoxidation of Simple Olefins by Chiral Bitetralin-Linked "Twin-Coronet" Porphyrin Catalysts

Catalytic and asymmetric epoxidation of styrenes and related aryl substituted olefins with the iron complexes of chiral bitetralin (Bitet)-linked "twin-coronet" porphyrins was performed with iodosylbenzene as an oxidant.Among two topological isomers of the catalyst, the eclipsed one (5b) showed higher enentioselectivity than the staggered (6b).With 5b, the resulting epoxides, except for the olefins bearing an electron-donating substituent, were obtained in good to excellent enantioselectivity (54-96percent ee), especially for the styrenes with electron-withdrawing substituent(s).Being different from other porphyrin-based chiral catalysts, the catalyst 5b is robust enough under the applied oxidation conditions to exhibit chiral epoxidation with the same ee and the same rate as those of the initial period of the reaction even after about 500 turnovers.The Bitet catalyst is superior in the epoxide enantioselectivity than the corresponding chiral binaphthalene (Binap)-linked catalyst (3b).In the reactions with the catalysts 3b and 5b, good correlation in epoxide ees was observed.Increase of the epoxide ee in the reaction with the Bitet catalyst was elucidated by the shape and size of the reaction cavities of the Bitet were tighter than those of the latter.The observed ees of the substituted styrene oxides showed good correlation with Σ?+ values of their substituent(s).In the reaction with the electron-deficient olefins, ?-?* interaction between the HOMO of the electron-rich Bitet auxiliary ring and the LUMO of the electron-deficient aryl ring of the substrate are pointed out as the key for the realization of high ees.Some nitrostyrenes, however, gave rather lower ees in spite of rather higher degree of their electron deficiency.This deviation was elucidated by the mismatching of their frontier orbitals.

Synthesis of Chiral Bitetralin-strapped "Twin Coronet" Porphyrins. Catalytic and Asymmetric Epoxidation of Styrene Derivatives

"Twin-coronet" porphyrins bearing optically active 1,1'-bitetrahydronaphthalene derivatives on the both faces of the porphyrin were prepared as enantioselective oxidation catalysts modeling on cytochrome P-450s.The eclipsed isomer of the corresponding iron(III) porphyrins catalyzed epoxidation of styrenes substituted with electron-withdrawing groups in high e.e. (61-89 percent) and high product selectivity.

Synthesis of Chiral "Twin Coronet" Porphyrins and Catalytic and Asymmetric Epoxidation of Olefins

Novel iron porphyrins, ''twin coronet'' porphyrins, which have chiral hydrophobic cavities consisting of binaphthalenes on their both faces are synthesized, and found to catalyze asymmetric epoxidation of olefins with high enantioselectivity.