138715-73-8Relevant articles and documents
Asymmetric Epoxidation of Simple Olefins by Chiral Bitetralin-Linked "Twin-Coronet" Porphyrin Catalysts
Naruta, Yoshinori,Ishihara, Nobuo,Tani, Fumito,Maruyama, Kazuhiro
, p. 158 - 166 (1993)
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.
Asymmetric epoxidation of alkenes and benzylic hydroxylation with P450tol monooxygenase from Rhodococcus coprophilus TC-2
Li, Aitao,Wu, Shuke,Adams, Joseph P.,Snajdrova, Radka,Li, Zhi
, p. 8771 - 8774 (2014/07/22)
P450tol monooxygenase was discovered as a unique and highly enantioselective enzyme for asymmetric epoxidation of some terminal alkenes containing electron-withdrawing groups and benzylic hydroxylation of several ethylbenzenes giving the corresponding useful and valuable products, such as (R)-2- and 3-substituted styrene oxides, (S)-4-substituted styrene oxides, and (S)-benzylic alcohols, in high ee.
A novel method for the synthesis of chiral epoxides from styrene derivatives using chiral acids in presence of Pseudomonas lipase G6 [PSL G6] and hydrogen peroxide
Sarma, Kuladip,Bhati, Nishi,Borthakur, Naleen,Goswami, Amrit
, p. 8735 - 8741 (2008/02/09)
Chiral epoxidation of styrene and its derivatives was carried out using series of chiral acids and urea hydrogen peroxide (UHP) or aqueous hydrogen peroxide (50%) in two phases under the catalytic influence of immobilized Pseudomonas lipase G6 [PSL G6] at 25-55 °C. A moderate to good yield and enantioselectivities of chiral epoxides were obtained.
