504-03-0Relevant articles and documents
Low-CTE photosensitive polyimide based on semialicyclic poly(amic acid) and photobase generator
Ogura, Tomohito,Higashihara, Tomoya,Ueda, Mitsuru
, p. 1317 - 1323 (2010)
A negative-type photosensitive polyimide (PSPI) based on semialicyclic poly(amic acid) (PAA), poly( frans-1, 4-cyclohexylenediphenylene amic acid), and {[(4, 5-dimethoxy-2-nitrobenzyl)oxy]carbonyl]} 2, 6-dimethylpiperidlne (DNCDP) as a photobase generator has been developed as a next-generation buffer coat material. The semialicyclic PAA was synthesized from 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride and frans1, 4-cyclohexyldiamine in the presence of acetic acid, and the PAA polymerization solution was directly used for PSPI formulation. This PSPI, consisting of PAA (80 wt %) and DNCDP (20 wt %), showed high sensitivity of 70 mJ/cm2 and high contrast of 10.3, when it was exposed to a 365-nm line (i-line), postexposure baked at 190 °C for 5 min, and developed with 2, 38 wt % tetramethylammonium hydroxide aqueous solution containing 20 wt % isopropanol at 25 °C. A clear negative image of 6-μm line and space pattern was printed on a film, which was exposed to 500 mJ/cm2 of i-line by a contact printing mode and fully converted to poly(trans-1, 4-cyclohexylenebiphenylene imide) pattern upon heating at 250 °C for 1 h. The PSPI film had a low coefficient of thermal expansion of 16 ppm/K compared to typical PIs, such as prepared from 3, 3', 4, 4'-biphenyltetracarboxylic dianhyariae ana 4, 4'-oxydianiline
Borenium-Catalyzed Reduction of Pyridines through the Combined Action of Hydrogen and Hydrosilane
Clarke, Joshua J.,Maekawa, Yuuki,Nambo, Masakazu,Crudden, Cathleen M.
supporting information, p. 6617 - 6621 (2021/09/02)
Mesoionic carbene-stabilized borenium ions efficiently reduce substituted pyridines to piperidines in the presence of a hydrosilane and a hydrogen atmosphere. Control experiments and deuterium labeling studies demonstrate reversible hydrosilylation of the pyridine, enabling full reduction of the N-heterocycle under milder conditions. The silane is a critical reaction component to prevent adduct formation between the piperidine product and the borenium catalyst.
Hydrogenation of N-Heteroarenes Using Rhodium Precatalysts: Reductive Elimination Leads to Formation of Multimetallic Clusters
Kim, Sangmin,Loose, Florian,Bezdek, Máté J.,Wang, Xiaoping,Chirik, Paul J.
, p. 17900 - 17908 (2019/11/19)
A rhodium-catalyzed method for the hydrogenation of N-heteroarenes is described. A diverse array of unsubstituted N-heteroarenes including pyridine, pyrrole, and pyrazine, traditionally challenging substrates for hydrogenation, were successfully hydrogenated using the organometallic precatalysts, [(η5-C5Me5)Rh(N-C)H] (N-C = 2-phenylpyridinyl (ppy) or benzo[h]quinolinyl (bq)). In addition, the hydrogenation of polyaromatic N-heteroarenes exhibited uncommon chemoselectivity. Studies into catalyst activation revealed that photochemical or thermal activation of [(η5-C5Me5)Rh(bq)H] induced C(sp2)-H reductive elimination and generated the bimetallic complex, [(η5-C5Me5)Rh(μ2,η2-bq)Rh(η5-C5Me5)H]. In the presence of H2, both of the [(η5-C5Me5)Rh(N-C)H] precursors and [(η5-C5Me5)Rh(μ2,η2-bq)Rh(η5-C5Me5)H] converted to a pentametallic rhodium hydride cluster, [(η5-C5Me5)4Rh5H7], the structure of which was established by NMR spectroscopy, X-ray diffraction, and neutron diffraction. Kinetic studies on pyridine hydrogenation were conducted with each of the isolated rhodium complexes to identify catalytically relevant species. The data are most consistent with hydrogenation catalysis prompted by an unobserved multimetallic cluster with formation of [(η5-C5Me5)4Rh5H7] serving as a deactivation pathway.
Hydrogenation of Pyridines Using a Nitrogen-Modified Titania-Supported Cobalt Catalyst
Chen, Feng,Li, Wu,Sahoo, Basudev,Kreyenschulte, Carsten,Agostini, Giovanni,Lund, Henrik,Junge, Kathrin,Beller, Matthias
supporting information, p. 14488 - 14492 (2018/10/26)
Novel heterogeneous catalysts were prepared by impregnation of titania with a solution of cobalt acetate/melamine and subsequent pyrolysis. The resulting materials show an unusual nitrogen-modified titanium structure through partial implementation of nitrogen into the support. The optimal catalyst displayed good activity and selectivity for challenging pyridine hydrogenation under acid free conditions in water as solvent.
Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
Ji, Pengfei,Song, Yang,Drake, Tasha,Veroneau, Samuel S.,Lin, Zekai,Pan, Xiandao,Lin, Wenbin
, p. 433 - 440 (2018/01/17)
Titania (TiO2) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
Selective hydrogenation of N-heterocyclic compounds using Ru nanocatalysts in ionic liquids
Konnerth, Hannelore,Prechtl, Martin H. G.
supporting information, p. 2762 - 2767 (2017/07/24)
N-Heterocyclic compounds have been tested in the selective hydrogenation catalysed by small 1-3 nm sized Ru nanoparticles (NPs) embedded in various imidazolium based ionic liquids (ILs). Particularly a diol-functionalised IL shows the best performance in the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline (1THQ) with up to 99% selectivity.
Hydrogenations at room temperature and atmospheric pressure with mesoionic carbene-stabilized borenium catalysts
Eisenberger, Patrick,Bestvater, Brian P.,Keske, Eric C.,Crudden, Cathleen M.
supporting information, p. 2467 - 2471 (2015/02/19)
1,2,3-Triazolylidene-based mesoionic carbene boranes have been synthesized in a convenient one-pot protocol from the corresponding 1,2,3-triazolium salts, base, and borane. Borenium ions are obtained by hydride abstraction and serve as catalysts in mild hydrogenation reactions of imines and unsaturated N-heterocycles at ambient pressure and temperature.
A molecular iron catalyst for the acceptorless dehydrogenation and hydrogenation of N-heterocycles
Chakraborty, Sumit,Brennessel, William W.,Jones, William D.
supporting information, p. 8564 - 8567 (2014/07/07)
A well-defined iron complex (3) supported by a bis(phosphino)amine pincer ligand efficiently catalyzes both acceptorless dehydrogenation and hydrogenation of N-heterocycles. The products from these reactions are isolated in good yields. Complex 3, the active catalytic species in the dehydrogenation reaction, is independently synthesized and characterized, and its structure is confirmed by X-ray crystallography. A trans-dihydride intermediate (4) is proposed to be involved in the hydrogenation reaction, and its existence is verified by NMR and trapping experiments.
Exceptional rate enhancements and improved diastereoselectivities through chelating diamide coordination in intramolecular alkene hydroaminations catalyzed by yttrium and neodymium amido complexes
Kim, Young Kwan,Livinghouse, Tom
, p. 3645 - 3647 (2007/10/03)
Modification of the metal center in the complexes [Ln{N(TMS)2}3] (Ln = Y, Nd; TMS = trimethylsilyl) is readily achieved by amine elimination in the presence of sterically hindered chelating diamines to provide complexes with substantially augmented catalytic activities and improved stereoselectivities in intramolecular alkene hydroamination (see scheme).
Substituted amino silane compounds and catalyst for the polymerization of alpha-olefins containing them
-
, (2008/06/13)
An aminosilane of the formula: where R1is a linear or branched C1-22alkyl or C3-22cycloalkyl, which may be substituted with at least one halogen atom; R2is a bis(linear or branched C1-22alkyl or C3-22cycloalkyl)amino, a substituted piperidinyl, a substituted pyrrolidinyl, decahydroquinolinyl, 1,2,3,4-tetrahydroquinolinyl or 1,2,3,4-tetrahydroisoquinolinyl, with the substituent selected from the group consisting of C1-8alkyl, phenyl, C1-8linear or branched alkylsubstituted phenyl and trimethylsilyl, with the proviso that when the substituent is C1-8alkyl, there must be at least two such substituent groups present and R1must contain halogen; and R3is a linear or branched C1-8alkyl or C3-8cycloalkyl. The aminosilane may be reacted with an aluminum-alkyl compound and a solid component comprising a titanium compound having at least one titanium-halogen bond and an electron donor, both supported on an activated anhydrous magnesium dihalide, to form a catalyst for polymerization of olefins.
