4541-87-1Relevant articles and documents
Asymmetric Epoxidation of Olefins Catalyzed by Substituted Aminobenzimidazole Manganese Complexes Derived from L-Proline
Tian, Jing,Lin, Jin,Zhang, Jisheng,Xia, Chungu,Sun, Wei
supporting information, p. 593 - 600 (2021/11/16)
A family of manganese complexes [Mn(Rpeb)(OTf)2] (peb=1-(1-ethyl-1H-benzo[d]imidazol-2-yl)-N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl) pyrrolidin-2-yl)methyl)-N-methylmethanamine)) derived from L-proline has been synthesized and characterized, where R refers to the group at the diamine backbone. X-ray crystallographic analyses indicate that all the manganese complexes [Mn(Rpeb)(OTf)2] exhibit cis-α topology. These types of complexes are shown to catalyze the asymmetric epoxidation of olefins employing H2O2 as a terminal oxidant with up to 96% ee. Obviously, the R group of the diamine backbone can influence the catalytic activity and enantioselectivity in the asymmetric epoxidation of olefins. In particular, Mn(i-Prpeb)(OTf)2 bearing an isopropyl arm, cannot catalyze the epoxidation reaction with H2O2 as the oxidant. However, when PhI(OAc)2 is used as the oxidant instead, all the manganese complexes including Mn(i-Prpeb)(OTf)2 can promote the epoxidation reactions efficiently. Taken together, these results indicate that isopropyl substitution on the Rpeb ligand inhibits the formation of active Mn(V)-oxo species in the H2O2/carboxylic acid system via an acid-assisted pathway.
Effect of the Ligand Backbone on the Reactivity and Mechanistic Paradigm of Non-Heme Iron(IV)-Oxo during Olefin Epoxidation
Biswas, Jyoti Prasad,Ansari, Mursaleem,Paik, Aniruddha,Sasmal, Sheuli,Paul, Sabarni,Rana, Sujoy,Rajaraman, Gopalan,Maiti, Debabrata
supporting information, p. 14030 - 14039 (2021/05/11)
The oxygen atom transfer (OAT) reactivity of the non-heme [FeIV(2PyN2Q)(O)]2+ (2) containing the sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins. The ferryl-oxo complex 2 shows excellent OAT reactivity during epoxidations. The steric encumbrance and electronic effect of the ligand influence the mechanistic shuttle between OAT pathway I and isomerization pathway II (during the reaction stereo pure olefins), resulting in a mixture of cis-trans epoxide products. In contrast, the sterically less hindered and electronically different [FeIV(N4Py)(O)]2+ (1) provides only cis-stilbene epoxide. A Hammett study suggests the role of dominant inductive electronic along with minor resonance effect during electron transfer from olefin to 2 in the rate-limiting step. Additionally, a computational study supports the involvement of stepwise pathways during olefin epoxidation. The ferryl bend due to the bulkier ligand incorporation leads to destabilization of both (Formula presented.) and (Formula presented.) orbitals, leading to a very small quintet–triplet gap and enhanced reactivity for 2 compared to 1. Thus, the present study unveils the role of steric and electronic effects of the ligand towards mechanistic modification during olefin epoxidation.
Process for isomerizing and converting (Z)-olefins to (E)-olefins
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Paragraph 0136-0138, (2020/03/25)
The invention belongs to the technical field of metal catalytic synthesis, and discloses a method for isomerizing and converting (Z)-olefins into (E)-olefins. The (E)-olefins are prepared through a reaction at -30-80 DEG C for 0.5-48 h by using a combination of CoX2 and a PNP or PAO ligand as a catalyst in the presence of an activating reagent; and a molar ratio of the (Z)-olefins to the CoX2 to the PNP or PAO ligand to the activating reagent is 1:(0.00001-0.10):(0.00001-0.10):(0.00003-0.30). The catalyst used in the invention is the combination of the cheap metal cobalt salt and the simple and easily available ligand, no other toxic transition metal (such as ruthenium, rhodium and palladium) salt is added in the reaction, and the method also has the advantages of cheap and easily available raw material, good functional group tolerance, mild reaction conditions, simplicity in operation, and e atom economy of 100%.
