618-36-0Relevant academic research and scientific papers
Optimizing the deprotection of the amine protecting p-methoxyphenyl group in an automated microreactor platform
Koch, Kaspar,Van Weerdenburg, Bram J.A.,Verkade, Jorge M.M.,Nieuwland, Pieter J.,Rutjes, Floris P.J.T.,Van Hest, Jan C.M.
, p. 1003 - 1006 (2009)
Three factors (temperature, stoichiometry and reaction temperature) were investigated in continuous flow microreactors in an automated fashion for optimization of the removal of the p- methoxyphenyl (PMP) protecting group, thereby consuming only minute amounts of substrate (0.2 mg/sample). The optimal reaction conditions were also applied to a larger microreactor system, in which the corresponding free amine was obtained at a preparative scale.
Key Parameters for the Synthesis of Active and Selective Nanostructured 3d Metal Catalysts Starting from Coordination Compounds – Case Study: Nickel Mediated Reductive Amination
Klarner, Mara,Blach, Patricia,Wittk?mper, Haiko,de Jonge, Niels,Papp, Christian,Kempe, Rhett
, p. 3257 - 3261 (2021)
The design of nanostructured catalysts based on earth-abundant metals that mediate important reactions efficiently, selectively and with a broad scope is highly desirable. Unfortunately, the synthesis of such catalysts is poorly understood. We report here on highly active Ni catalysts for the reductive amination of ketones by ammonia employing hydrogen as a reducing agent. The key functions of the Ni-salen precursor complex during catalyst synthesis have been identified: (1) Ni-salen complexes sublime during catalyst synthesis, which allows molecular dispersion of the metal precursor on the support material. (2) The salen ligand forms a nitrogen-doped carbon shell by decomposition, which embeds and stabilizes the Ni nanoparticles on the γ-Al2O3 support. (3) Parameters, such as flow rate of the pyrolysis gas, determine the carbon supply for the embedding process of Ni nanoparticles.
Iridium-Catalyzed Hydroiodination and Formal Hydroamination of Olefins with N-Iodo Reagents and Molecular Hydrogen: An Umpolung Strategy
Wen, Jialin,Yang, Huaxin,Zhang, Xumu,Zhang, Zhihan,Zhou, Yang
, p. 1842 - 1847 (2022/03/14)
We herein report a convenient method to convert olefins to organic iodides and amines using an Ir/ZhaoPhos catalyst, molecular hydrogen, and an electrophilic iodine(I) reagent. High yields and regioselectivities were obtained under mild conditions. In addition, basic workup with potassium carbonate leads to C-N products. Control experiments and DFT calculations tentatively excluded the pathway involving the in situ formation of HI. Instead, a catalytic cycle involving the hydrogenation of the haliranium ion intermediate was proposed.
Direct reductive amination of ketones with ammonium salt catalysed by Cp*Ir(iii) complexes bearing an amidato ligand
Dai, Zengjin,Pan, Ying-Min,Wang, Shou-Guo,Yin, Qin,Zhang, Xumu
supporting information, p. 8934 - 8939 (2021/11/04)
A series of half-sandwich Ir(iii) complexes1-6bearing an amidato bidentate ligand were conveniently synthesized and applied to the catalytic Leuckart-Wallach reaction to produce racemic α-chiral primary amines. With 0.1 mol% of complex1, a broad range of ketones, including aryl ketones, dialkyl ketones, cyclic ketones, α-keto acids, α-keto esters and diketones, could be transformed to their corresponding primary amines with moderate to excellent yields (40%-95%). Asymmetric transformation was also attempted with chiral Ir complexes3-6, and 16% ee of the desired primary amine was obtained. Despite the unsatisfactory enantio-control achieved so far, the current exploration might stimulate more efforts towards the discovery of better chiral catalysts for this challenging but important transformation.
Air Stable Iridium Catalysts for Direct Reductive Amination of Ketones
Polishchuk, Iuliia,Sklyaruk, Jan,Lebedev, Yury,Rueping, Magnus
supporting information, p. 5919 - 5922 (2021/03/08)
Half-sandwich iridium complexes bearing bidentate urea-phosphorus ligands were found to catalyze the direct reductive amination of aromatic and aliphatic ketones under mild conditions at 0.5 mol % loading with high selectivity towards primary amines. One of the complexes was found to be active in both the Leuckart–Wallach (NH4CO2H) type reaction as well as in the hydrogenative (H2/NH4AcO) reductive amination. The protocol with ammonium formate does not require an inert atmosphere, dry solvents, as well as additives and in contrast to previous reports takes place in hexafluoroisopropanol (HFIP) instead of methanol. Applying NH4CO2D or D2 resulted in a high degree of deuterium incorporation into the primary amine α-position.
Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis
Funk, Pierre,Richrath, Ruben B.,Bohle, Fabian,Grimme, Stefan,Gans?uer, Andreas
, p. 5482 - 5488 (2021/02/03)
Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening. An H-atom transfer, to generate a benzylic radical, serves as a radical translocation step, and an organometallic oxygen rebound as a reductive elimination. The reaction mechanism was studied by high-level dispersion corrected hybrid functional DFT with implicit solvation. The low-energy conformational space was searched by the efficient CREST program. The stereoselectivity was deduced from the lowest lying benzylic radical structures and their conformations are controlled by hyperconjugative interactions and steric interactions between the titanocene catalyst and the aryl groups of the substrate. An interesting mechanistic aspect is that the oxidation of the benzylic center occurs under reducing conditions.
Co-Catalyzed Synthesis of Primary Amines via Reductive Amination employing Hydrogen under very mild Conditions
Elfinger, Matthias,Sch?nauer, Timon,Thom?, Sabrina L. J.,St?glich, Robert,Drechsler, Markus,Zobel, Mirijam,Senker, Jürgen,Kempe, Rhett
, p. 2360 - 2366 (2021/05/03)
Nanostructured and reusable 3d-metal catalysts that operate with high activity and selectivity in important chemical reactions are highly desirable. Here, a cobalt catalyst was developed for the synthesis of primary amines via reductive amination employing hydrogen as the reducing agent and easy-to-handle ammonia, dissolved in water, as the nitrogen source. The catalyst operates under very mild conditions (1.5 mol% catalyst loading, 50 °C and 10 bar H2 pressure) and outperforms commercially available noble metal catalysts (Pd, Pt, Ru, Rh, Ir). A broad scope and a very good functional group tolerance were observed. The key for the high activity seemed to be the used support: an N-doped amorphous carbon material with small and turbostratically disordered graphitic domains, which is microporous with a bimodal size distribution and with basic NH functionalities in the pores.
Indirect reduction of CO2and recycling of polymers by manganese-catalyzed transfer hydrogenation of amides, carbamates, urea derivatives, and polyurethanes
Liu, Xin,Werner, Thomas
, p. 10590 - 10597 (2021/08/20)
The reduction of polar bonds, in particular carbonyl groups, is of fundamental importance in organic chemistry and biology. Herein, we report a manganese pincer complex as a versatile catalyst for the transfer hydrogenation of amides, carbamates, urea derivatives, and even polyurethanes leading to the corresponding alcohols, amines, and methanol as products. Since these compound classes can be prepared using CO2as a C1 building block the reported reaction represents an approach to the indirect reduction of CO2. Notably, these are the first examples on the reduction of carbamates and urea derivatives as well as on the C-N bond cleavage in amides by transfer hydrogenation. The general applicability of this methodology is highlighted by the successful reduction of 12 urea derivatives, 26 carbamates and 11 amides. The corresponding amines, alcohols and methanol were obtained in good to excellent yields up to 97%. Furthermore, polyurethanes were successfully converted which represents a viable strategy towards a circular economy. Based on control experiments and the observed intermediates a feasible mechanism is proposed.
Scope and limitations of reductive amination catalyzed by half-sandwich iridium complexes under mild reaction conditions
Nguyen, Dat P.,Sladek, Rudolph N.,Do, Loi H.
supporting information, (2020/07/15)
The conversion of aldehydes and ketones to 1° amines could be promoted by half-sandwich iridium complexes using ammonium formate as both the nitrogen and hydride source. To optimize this method for green chemical synthesis, we tested various carbonyl substrates in common polar solvents at physiological temperature (37 °C) and ambient pressure. We found that in methanol, excellent selectivity for the amine over alcohol/amide products could be achieved for a broad assortment of carbonyl-containing compounds. In aqueous media, selective reduction of carbonyls to 1° amines was achieved in the absence of acids. Unfortunately, at Ir catalyst concentrations of 1 mM in water, reductive amination efficiency dropped significantly, which suggest that this catalytic methodology might be not suitable for aqueous applications where very low catalyst concentration is required (e.g., inside living cells).
Ambient-Temperature Synthesis of Primary Amines via Reductive Amination of Carbonyl Compounds
Xie, Chao,Song, Jinliang,Hua, Manli,Hu, Yue,Huang, Xin,Wu, Haoran,Yang, Guanying,Han, Buxing
, p. 7763 - 7772 (2020/08/21)
Efficient synthesis of primary amines via low-temperature reductive amination of carbonyl compounds using NH3 and H2 as the nitrogen and hydrogen resources is highly desired and challenging in the chemistry community. Herein, we employed naturally occurring phytic acid as a renewable precursor to fabricate titanium phosphate (TiP)-supported Ru nanocatalysts with different reduction degrees of RuO2 (Ru/TiP-x, x represents the reduction temperature) by combining ball milling and molten-salt processes. Very interestingly, the obtained Ru/TiP-100 had good catalytic performance for the reductive amination of carbonyl compounds at ambient temperature, resulting from the synergistic cooperation of the support (TiP) and the Ru/RuO2 with a suitable proportion of Ru0 (52%). Various carbonyl compounds could be efficiently converted into the corresponding primary amines with high yields. More importantly, the conversion of other substrates with reducible groups could also be achieved at ambient temperature. Detailed investigations indicated that the partially reduced Ru and the support (TiP) were indispensable. The high activity and selectivity of Ru/TiP-100 catalyst originates from the relatively high acidity and the suitable electron density of metallic Ru0.
