1528-30-9Relevant academic research and scientific papers
Enhanced radical delivery from aldoxime esters for EPR and ring closure applications
McCarroll, Andrew J.,Walton, John C.
, p. 351 - 352 (2000)
Arylmethaniminyl and alkyl radicals were generated from di- and tri- methoxyphenyl aldoxime esters, by photolysis in the presence of 4- methoxyacetophenone, and were detected by EPR spectroscopy: good yields of cyclised products were isolated from suitably unsaturated alkyl substituents.
Oligomerization and simultaneous cyclization of ethylene to methylenecyclopentane catalyzed by zirconocene complexes
Wang, Mei,Shen, Yumei,Qian, Mingxing,Li, Rui,He, Ren
, p. 143 - 146 (2000)
The oligomerization of ethylene catalyzed by Cp2ZrL2 (L=Cl, Me, OC6H4-Me-p) with ethylaluminoxane or Et3Al as cocatalyst (Al/Zr=100, 150°C, P(C2H4)=1.4 MPa) afforded not only common chain oligomers but also a cyclic oligomer, methylenecyclopentane. The selectivity of methylenecyclopentane reached 39% under optimal conditions. The addition of C5H5N to the catalytic system of Cp2ZrCl2/Et3Al was capable of further improving the selectivity of methylenecyclopentane to 43%.
Product-Determining Steps in Gas-Phase Bronsted Acid-Base REactions. Deprotonation of 1-Methylcyclopentyl Cation by Amine Bases
Redman, Eric W.,Morton, Thomas Hellman
, p. 5701 - 5708 (1986)
Experimental results are presented for deprotonation of 1-methylcyclopentyl cation (1) by ammonia, trimethylamine, and 1-methylcyclopentylamine at pressures below 10-3 Torr, which yields two neutral products, 1-methylcyclopentene (2) and methylenecyclopentane (3).The isomer ratio varies from 2:3 = 2.74 for trimethylamine, consistent with previous reports.FTMS measurement of ion-molecule reaction rates of 1 plus ammonia gives an efficiency of 0.34 when 1 is generated by a 20-70 eV electron impact on bromocyclohexane.REaction of the predeuterated cation 1-d11 with ammonia yields products that reveal only a very low level of hydrogen scrambling between acid and base.Isotope effects on the reaction rate and the neutral product ratio, determined from experiments using 1-d11 or ND3, are found to be small.Two mechanistic alternatives are discussed: Lewis (in which covalent acid-base complexes are formed) and Eigen (in which hydrogen-bonded intermediates are formed).Reaction of 1-d11 with 1-methylcyclopentylamine shows only a small amount of interchange of deuterated and undeuterated alkyl groups, which argues against a Lewis mechanism as an obligatory pathway.Experimental results are interpreted in terms of orbiting intermediates, in which acidic C-H bonds and the basic nitrogen experience large deviations from collinearity.More than one subsequent step is required for the reactants to engage chemically.In order for Eigen mechanisms to operate, a C-H bond must point toward the nitrogen, which requires loss of some internal degrees of freedom.For proton transfer to be completed, the nitrogen lone pair must be pointed along the C-H...N axis, which requires loss of additional degrees of freedom.Progress of the reaction beyond the initially formed orbiting intermediate is described by a scheme in which these stages of approach to reactive orientaion represent discrete steps.
Nickel Hydride Complexes Supported by a Pyrrole-Derived Phosphine Ligand
Collett, Joel D.,Guan, Hairong,Krause, Jeanette A.
, p. 345 - 353 (2022/02/16)
The synthesis of two nickel hydride complexes bearing the pyrrole-derived phosphine ligand CyPNH (2-(dicyclohexylphosphino)methyl-1H-pyrrole) was developed, namely, (κP-CyPNH)(κP,κN-CyPN)NiH and the acid-stable trans-(κP-CyPNH)2Ni(OAc)H·HOAc. (κP-CyPNH)(κP,κN-CyPN)NiH stoichiometrically reduces benzaldehyde and acetophenone in a metal-ligand cooperative manner and catalytically dimerizes ethylene and cycloisomerizes 1,5-cyclooctadiene and 1,5-hexadiene. trans-(κP-CyPNH)2Ni(OAc)H·HOAc, available from the protonation of (κP-CyPNH)(κP,κN-CyPN)NiH with acetic acid, catalyzes the cycloisomerization of 1,5-cyclooctadiene more effectively and produces the less thermodynamically favored cycloisomers of 1,5-cyclooctadiene.
Synthesis of sp 3-Enriched β-Fluoro Sulfonyl Chlorides
Gurbanov, Rustam,Sokolov, Andriy,Golovach, Sergey,Melnykov, Kostiantyn,Dobrydnev, Alexey V.,Grygorenko, Oleksandr O.
, p. 1771 - 1784 (2020/12/28)
A three-step approach to the synthesis of sp 3-enriched β-fluoro sulfonyl chlorides starting from alkenes is reported. The method was successfully applied to a wide range of acyclic and cyclic substrates, bearing either an exocyclic or an endocyclic double bond. The procedure worked with a wide range of substrates and tolerated a number of functional and protecting groups. Moreover, the target cyclic compounds were obtained as single cis diastereomers on a multigram scale. The title compounds are promising building blocks for drug discovery that can be used to obtain sp 3-enriched β-fluoro and α,β-unsaturated sulfonamides.
Phospholane-Based Ligands for Chromium-Catalyzed Ethylene Tri- And Tetramerization
Boelter, Scott D.,Davies, Dan R.,Klosin, Jerzy,Margl, Peter,Milbrandt, Kara A.,Mort, Darrek,Rosen, Mari S.,Vanchura, Britt A.,Wilson, David R.,Wiltzius, Molly
supporting information, (2020/02/27)
Chromium complexes with bis(phospholane) ligands were synthesized and evaluated for ethylene tetramerization in a high-throughput reactor. Three ligand parameters - the phospholane substituent, the ligand backbone, and the type of phosphine (cyclic vs acyclic) - were investigated. The size of the phospholane substituent was found to impact the selectivity of the resulting catalysts, with smaller substituents leading to the production of larger proportions of 1-octene. Changing the ligand backbone from 1,2-phenylene to ethylene did not impact catalysis, but the use of acyclic phosphines in place of the cyclic phospholanes had a detrimental effect on catalytic activity. Selected phospholane-chromium complexes were evaluated in a 300 mL Parr reactor at 70 °C and 700 psi of ethylene pressure, and the ethylene oligomerization performance was consistent with that observed in the smaller, high-throughput reactor. MeDuPhos-CrCl3(THF) (MeDuPhos = 1,2-bis(2,5-dimethylphospholano)benzene; THF = tetrahydrofuran) gave activity and selectivity for 1-octene (54.8 wt %) similar to the state-of-the-art i-PrPNP-CrCl3(THF) (64.0 wt %) (PNP = bis(diphenylphosphino)amine), while EtDuPhos-CrCl3(THF) (EtDuPhos = 1,2-bis(2,5-diethylphospholano)benzene) exhibited even higher activity, with catalyst selectivity shifted toward 1-hexene production (90 wt %). These results are surprising, given the prevalence of the aryl phosphine motif in ligands used in ethylene oligomerization catalysts and the inferior performance of previously reported catalysts with alkyl phosphine-containing ligands.
Ethylene Tetramerisation: A Structure-Selectivity Correlation
Makume, Boitumelo F.,Holzapfel, Cedric W.,Maumela, Munaka C.,Willemse, J. Alexander,van den Berg, Jan A.
, p. 2308 - 2315 (2020/11/03)
The effect of ethylene tetramerisation ligand structures on 1-octene selectivity is well studied. However, by-product formation is less understood. In this work, a range of PNP ligand structures are correlated with the full product selectivity and with catalyst activity. As steric bulk on the N-substituent increases, the product selectivity shifts from >10 % to 3% of both C6 cyclics and C16+ by-products. 1-Octene peaks at ca. 70%. Thereafter, only 1-hexene increases. Similar selectivity changes were observed for ortho-Ph-substituted PNP ligands. The C10-14 selectivity was less affected by the ligand structure. The ligand effect on the changes in selectivity is explained mechanistically. Lastly, an increase in ligand steric bulk was found to improve catalyst activity and reduce polymer formation by an order of magnitude. It is proposed that steric bulk promotes formation of cationic catalytic species which are responsible for selective ethylene oligomerisation.
Catalyst Systems and Ethylene Oligomerization Method
-
Paragraph 0170-0172, (2019/06/14)
Disclosed herein is a catalyst system comprising (i) a heterocyclic 2-[(phosphinyl)aminyl]imine transition metal compound complex having Structure I wherein T is oxygen or sulfur, R1 and R2 are each independently a C1 to C20 organyl group consisting essentially of inert functional groups, R3 is hydrogen or a C1 to C20 organyl group, L is a C1 to C20 organylene group consisting essentially of inert functional groups, MXp represents a transition metal compound where M is a transition metal, X is a monoanion, and p is an integer from 1 to 6, Q is a neutral ligand, and q ranges from 0 to 6, and (ii) an organoaluminum compound. Also disclosed herein is a process comprising contacting (i) ethylene, (ii) a catalyst system comprising (a) a heterocyclic transition metal compound complex having Structure I as described herein and (b) an organoaluminum compound, and (iii) optionally hydrogen to form an oligomer product.
Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands
Newland, Robert J.,Smith, Alana,Smith, David M.,Fey, Natalie,Hanton, Martin J.,Mansell, Stephen M.
, p. 1062 - 1073 (2018/03/30)
Desilylation of the 2-phosphinophosphinine 2-PPh2-3-Me-6-SiMe3-PC5H2 with HCl gave 2-PPh2-3-Me-PC5H3, demonstrating the late-stage modification of this bidentate heterocyclic lig
α-Alkylidene-γ-butyrolactone Formation via Bi(OTf)3-Catalyzed, Dehydrative, Ring-Opening Cyclizations of Cyclopropyl Carbinols: Understanding Substituent Effects and Predicting E/Z Selectivity
Sandridge, Matthew J.,McLarney, Brett D.,Williams, Corey W.,France, Stefan
, p. 10883 - 10897 (2017/10/27)
A Bi(OTf)3-catalyzed ring-opening cyclization of (hetero)aryl cyclopropyl carbinols to form α-alkylidene-γ-butyrolactones (ABLs) is reported. This transformation represents different chemoselectivity from previous reports that demonstrated formation of (hetero)aryl-fused cyclohexa-1,3-dienes upon acid-promoted cyclopropyl carbinol ring opening. ABLs are obtained in up to 89% yield with a general preference for the E-isomers. Mechanistically, Bi(OTf)3 serves as a stable and easy to handle precursor to TfOH. TfOH then catalyzes the formation of cyclopropyl carbinyl cations, which undergo ring opening, intramolecular trapping by the neighboring ester group, subsequent hydrolysis, and loss of methanol resulting in the formation of the ABLs. The nature and relative positioning of the substituents on both the carbinol and the cyclopropane determine both chemo- and stereoselective outcomes. Carbinol substituents determine the extent of cyclopropyl carbinyl cation formation. The cyclopropane donor substituents determine the overall reaction chemoselectivity. Weakly stabilizing or electron-poor donor groups provide better yields of the ABL products. In contrast, copious amounts of competing products are observed with highly stabilizing cyclopropane donor substituents. Finally, a predictive model for E/Z selectivity was developed using DFT calculations.
