637-50-3Relevant academic research and scientific papers
Isolation, Characterization, and Reactivity of Fe8Me12-: Kochi's S = 1/2 Species in Iron-Catalyzed Cross-Couplings with MeMgBr and Ferric Salts
Mu?oz, Salvador B.,Daifuku, Stephanie L.,Brennessel, William W.,Neidig, Michael L.
, p. 7492 - 7495 (2016)
Iron-catalyzed cross-couplings with simple ferric salts have been known since the 1970s, pioneered by Kochi for cross-coupling using alkylmagnesium nucleophiles including MeMgBr. While Kochi observed the formation of a S = 1/2 iron species in reactions of simple ferric salts with MeMgBr proposed to be an iron(I) species, the identity of this species has remained undefined for nearly 40 years. Herein, we report the isolation and characterization of [MgCl(THF)5][Fe8Me12], which combined with EPR and MCD studies is shown to be consistent with Kochi's S = 1/2 species. Reaction studies with β-bromostyrene demonstrate that this species alone displays minimal reactivity but, when combined with additional MeMgBr, leads to rapid and selective formation of cross-coupled product.
HETEROPOLY ANION-ASSISTED Rh CATALYSIS REVEALED IN THE HOMOGENEOUS SELECTIVE HYDROGENATION
Urabe, Kazuo,Tanaka, Yoshiyuki,Izumi, Yusuke
, p. 1595 - 1596 (1985)
When coupled with lithium salt of heteropoly acid, the Wilkinson complex RhCl(PPh3)3 catalyst became very active and selective for the semihydrogenation of alkyne to alkene and, more interestingly, exhibited sharp substrate-selectivity in hydrogenation of substituted alkenes.
The N-Methylpyrrolidone (NMP) Effect in Iron-Catalyzed Cross-Coupling with Simple Ferric Salts and MeMgBr
Mu?oz, Salvador B.,Daifuku, Stephanie L.,Sears, Jeffrey D.,Baker, Tessa M.,Carpenter, Stephanie H.,Brennessel, William W.,Neidig, Michael L.
, (2018)
The use of N-methylpyrrolidone (NMP) as a co-solvent in ferric salt catalyzed cross-coupling reactions is crucial for achieving the highly selective, preparative scale formation of cross-coupled product in reactions utilizing alkyl Grignard reagents. Desp
An XPS study of the synergetic effect of gold and nickel supported on SiO2 in the catalytic isomerization of allylbenzene
Vasil'kov, Alexander Yu.,Nikolaev, Sergey A.,Smirnov, Vladimir V.,Naumkin, Alexander V.,Volkov, Ilija O.,Podshibikhin, Vladislav L.
, p. 268 - 270 (2007)
A synergetic effect and catalytic activity in allylbenzene isomerization have been found for the Au-Ni/SiO2 system prepared by metal-vapour synthesis.
Isomerization of 3-phenyl-1-propene (allylbenzene) over base catalysts
Marinas,Aramendia,Borau,Jimenez,Marinas,Urbano
, p. 556 - 559 (2002)
The isomerization of 3-phenyl-1-propylene (allylbenzene) to 1-phenyl-1-propylene (β-methylstyrene) (cis + trans) was studied as a new test reaction for base catalysts. The injection of pure trans-β-methylstyrene (without catalyst) only yielded 1% of the other isomer (cis-βmethylstyrene). The injection of pure trans-β-methylstyrene, in the presence of catalysts, yielded small quantities of allylbenzene and cis-β-methylstyrene. Poisoning of the catalyst with CO2 led to a sharp decrease in activity. The trans/cis ratio was ～ six for all the catalysts.
Stereoisomerism as an Origin of Different Reactivities of Ir(III) PC(sp3)P Pincer Catalysts
Belkova, Natalia V.,De-Botton, Sophie,Epstein, Lina M.,Filippov, Oleg A.,Gelman, Dmitri,Kirkina, Vladislava A.,Pavlov, Alexander A.,Shubina, Elena S.,Silantyev, Gleb A.,Titova, Ekaterina M.
, p. 11962 - 11975 (2020)
Two stereoisomers of pentacoordinate iridium(III) hydridochloride with triptycene-based PC(sp3)P pincer ligand (1,8-bis(diisopropylphosphino)triptycene), 1 and 2, differ by the orientation of hydride ligand relative to the bridgehead ring of triptycene. According to DFT/B3PW91/def2-TZVP calculations performed, an equatorial Cl ligand can relatively easily change its position in 1, whereas that is not the case in 2. Both complexes 1 and 2 readily bind the sixth ligand to protect the empty coordination site. Variable temperature spectroscopic (NMR, IR, and UV-visible) studies show the existence of two isomers of hexacoordinate complexes 1·MeCN, 2·MeCN, and 2·Py with acetonitrile or pyridine coordinated trans to hydride or trans to metalated C(sp3), whereas only the equatorial isomer is found for 1·Py. These complexes are stabilized by various intramolecular noncovalent C-H···Cl interactions that are affected by the rotation of isopropyls or pyridine. The substitution of MeCN by pyridine is slow yielding axial Py complexes as kinetic products and the equatorial Py complexes as thermodynamic products with faster reactions of 1·L. Ultimately, that explains the higher activity of 1 in the catalytic alkenes' isomerization observed for allylbenzene, 1-octene, and pent-4-enenitrile, which proceeds as an insertion/elimination sequence rather than through the allylic mechanism.
Identifying and Evading Olefin Isomerization Catalyst Deactivation Pathways Resulting from Ion-Tunable Hemilability
Dodge, Henry M.,Kita, Matthew R.,Chen, Chun-Hsing,Miller, Alexander J. M.
, p. 13019 - 13030 (2020)
Hemilabile ligands are found in many leading organometallic catalysts, but it can be challenging to tune the degree of hemilability in a particular catalyst. This work explores the impact of cation-tunable hemilability on the speciation of iridium(III) pincer-crown ether catalysts during high-activity olefin isomerization. Under conditions where strong cation-macrocycle interactions are fostered and terminal olefin has been consumed, labilization of the aza-crown ether group leads to an η6-arene complex, wherein the pincer ligand is metallated at a different position. Arene complexes of styrene, naphthalene, and mesitylene were independently synthesized and found to exhibit diminished catalytic activity for allylbenzene isomerization. In response to these findings, a previously unreported catalyst bearing a synthetically modified pincer ligand was designed, resulting in a refined system that maintains high activity even when arene complexes are formed.
Enantioselective hydroamination of unactivated terminal alkenes
Fan, Haoyu,Hartwig, John F.,Ma, Senjie,Roediger, Sven,Xi, Yumeng
supporting information, p. 532 - 542 (2022/02/11)
Asymmetric alkene hydroamination could be a direct route to valuable chiral amines from abundant feedstocks. However, most asymmetric hydroaminations have limited synthetic value because they require a large excess of alkene, occur with modest enantioselectivity, and proceed with limited tolerance of functional groups. We report an enantioselective, intermolecular hydroamination of unactivated terminal alkenes that occurs with equimolar amounts of alkene and amine, tolerates many functional groups, and occurs in high yield, with high enantioselectivity and turnover numbers. Mechanistic studies revealed factors, including reversibility of the addition, reversible oxidation of the product amine, competing isomerization of the alkene reactant, and unfavorable replacement of sacrificial ligands in standard catalyst precursors by the chiral bisphosphine, that needed to be addressed to achieve enantioselective N–H additions to alkenes.
Regioselective Deaminative Allylation of Aliphatic Amines via Dual Cobalt and Organophotoredox Catalysis
Sekino, Tomoyuki,Sato, Shunta,Yoshino, Tatsuhiko,Kojima, Masahiro,Matsunaga, Shigeki
supporting information, p. 2120 - 2124 (2022/03/27)
Despite the rapid progress in C-C bond-forming reactions using Katritzky salts, their deaminative allylation remains a challenge. Inspired by the metallaphotoredox-catalyzed allylic substitution regime, here, we report the deaminative allylation of Katritzky salts via cobalt/organophotoredox dual catalysis. This cross-electrophile coupling enables regioselective allylation using a variety of allylic esters, overcoming the substrate limitations of reported protocols. Mechanistic studies indicate the involvement of a π-allyl cobalt complex as a radicalophile that mediates C-C bond formation.
Impact of N-Aryl- and NHC Core-Substituents on the Coupling of Alkylzinc Nucleophiles: Is Bigger always Better?
Eckert, Philip,Organ, Michael G.
supporting information, (2022/05/17)
Bulky Pd?N-heterocyclic carbene (NHC) catalysts (e. g., N-(di-2,6-(3-pentyl)phenyl), IPent) have been shown to have significantly higher reactivity in a wide variety of cross-coupling applications (i. e., C?C, C?S, C?N) than less hindered variants (e. g., N-(di-2,6-(isopropyl)phenyl), IPr). Further, chlorinating the backbone of the NHC ring sees an even greater increase in reactivity. In the cross-coupling of (hetero)aryl electrophiles to secondary alkyl nucleophiles, making the N-aryl groups larger reduces the amount of β-hydride elimination leading to alkene byproducts and chlorinating the NHC core had an even greater effect, all but eliminating alkene formation. In the present study involving the cross-coupling of primary alkyl electrophiles and nucleophiles, a sharp and surprising reversal of all of the above trends was observed. Bulkier catalysts had generally slower rate of reaction and β-hydride elimination worsened leading to extensive amounts of alkene byproducts.
