Benzylamine Research Articles

Synthesis of Naturally Racemic Marilines B & C through Multicomponent Reactions Involving ortho-Quinone Methides and Various Nitrogen Nucleophiles

AbstractHerein, we report the first total synthesis of (±)-marilines B and C, as well as a failed approach to (±)-mariline A, by using our recently developed multicomponent reaction method, which involves the interception of ortho-quinone methides with various nitrogen nucleophiles to allow easy assembly of various benzylic amine cores with diverse substituents.

Chemoselective Catalytic Dehydrogenation of Benzylic Amines Driven by the TEtraQuinoline/FeCl2 Complex

AbstractA chemoselective dehydrogenation protocol for benzylic amines catalyzed by the TEtraQuinoline (TEQ)/FeCl2 complex is described. In combination with 2 equiv of tert‐butyl hydroperoxide, as little as 0.1 mol% of catalyst loading was sufficient to convert primary and secondary benzylic amines to the corresponding imines and dimerized imines, respectively. Subsequent hydrolysis of the imines allowed for removal of the benzyl group on the nitrogen atom. Nonaromatic carbon‐carbon multiple bonds and the O‐Bn group remained intact in the present protocol, providing a complementary deprotection procedure to reductive removal conditions exerted by Pd catalysis.

Metallaphotoredox‐Catalyzed Enantioselective Cross‐Electrophile Coupling Using Alcohols as Reducing Agents

AbstractThe cross‐electrophile coupling (XEC) represents a powerful strategy for C−C bond formation. However, controlling the enantioselectivity in these processes remains a challenge. Here, we report an unprecedented enantioselective XEC of α‐amino acid derivatives with aryl bromides, enabled by alcohols as reducing agents via Ni/photoredox catalysis. This mechanistically distinct approach exploits the ability of photocatalytically generated α‐hydroxyalkyl radicals to convert alkyl electrophiles to the corresponding alkyl radicals that are then enantioselectively coupled with aryl bromides. The readily scalable protocol allows modular access to valuable enantioenriched benzylic amines from abundant and inexpensive precursors, and is applicable to late‐stage diversification with broad functional group tolerance. Mechanistic studies rationalize the versatility of this alcohol‐based reactivity for radical generation and subsequent asymmetric cross‐coupling. We expect that this alcohol‐based cross‐coupling will render a general platform for the development of appealing yet challenging enantioselective XECs.

Metallaphotoredox-Catalyzed Enantioselective Cross-Electrophile Coupling Using Alcohols as Reducing Agents.

The cross-electrophile coupling (XEC) represents a powerful strategy for C-C bond formation. However, controlling the enantioselectivity in these processes remains an outstanding challenge. Here, we report an unprecedented enantioselective XEC of α-amino acid derivatives with aryl bromides, enabled by the identification of alcohols as reducing agents via Ni/photoredox catalysis. This mechanistically distinct approach exploits the ability of photocatalytically generated α-hydroxyalkyl radicals to convert alkyl electrophiles to the corresponding alkyl radicals that are then enantioselectively coupled with aryl bromides. The readily scalable protocol allows modular access to valuable enantioenriched benzylic amines from abundant and inexpensive precursors, and is applicable to late-stage diversification with broad functional group tolerance. Mechanistic studies rationalize the versatility of this alcohol-based reactivity for radical generation and subsequent asymmetric cross-coupling. We expect that this alcohol-based cross-coupling will render a general platform for the development of appealing yet challenging enantioselective XECs.

Solar Light Driven H2O2 Production and Selective Oxidations Using a Covalent Organic Framework Photocatalyst Prepared by a Multicomponent Reaction

AbstractA chemically stable 2D microporous COF (PMCR‐1) was synthesized via the multicomponent Povarov reaction. PMCR‐1 exhibits a remarkable and long‐term stable photocatalytic H2O2 production rate (60 h) from pure and sea water under visible light. The H2O2 production is markedly enhanced when benzyl alcohol (BA) is added as reductant, which is also due to a strong π–π interaction of BA with dangling phenyl moieties in the COF pores introduced by the multicomponent Povarov reaction. Motivated by the concomitant BA oxidation to benzaldehyde during H2O2 formation, the photocatalytic oxidation of various organic substrates such as benzyl amine and methyl sulfide derivatives was investigated. It is shown that the well‐defined micropores of PMCR‐1 enable size‐selective photocatalytic oxidation.

Solar Light Driven H2 O2 Production and Selective Oxidations Using a Covalent Organic Framework Photocatalyst Prepared by a Multicomponent Reaction.

A chemically stable 2D microporous COF (PMCR-1) was synthesized via the multicomponent Povarov reaction. PMCR-1 exhibits a remarkable and long-term stable photocatalytic H2 O2 production rate (60 h) from pure and sea water under visible light. The H2 O2 production is markedly enhanced when benzyl alcohol (BA) is added as reductant, which is also due to a strong π-π interaction of BA with dangling phenyl moieties in the COF pores introduced by the multicomponent Povarov reaction. Motivated by the concomitant BA oxidation to benzaldehyde during H2 O2 formation, the photocatalytic oxidation of various organic substrates such as benzyl amine and methyl sulfide derivatives was investigated. It is shown that the well-defined micropores of PMCR-1 enable size-selective photocatalytic oxidation.

Microwave-Assisted Synthesis of E-Aldimines, N-Heterocycles, and H2 by Dehydrogenative Coupling of Benzyl Alcohol and Aniline Derivatives Using CoCl2 as a Catalyst.

The acceptorless dehydrogenative coupling (ADC) between alcohols and amines to produce imines has been achieved mostly by employing precious-metal-based complexes or complexes of earth-abundant metal ions with sensitive and complicated ligand systems as catalysts mostly under harsh reaction conditions. Methodologies using readily available earth-abundant metal salts as catalysts without the requirement of ligand, oxidant, or any external additives are not explored. We report an unprecedented microwave-assisted CoCl2-catalyzed acceptorless dehydrogenative coupling of benzyl alcohol and amine for the synthesis of E-aldimines, N-heterocycles, and H2 under mild condition, without any complicated exogenous ligand template, oxidant, or other additives. This environmentally benign methodology exhibits broad substrate scope (43 including 7 new products) with fair functional-group tolerance on the aniline ring. Detection of metal-associated intermediate by gas chromatography (GC) and HRMS, H2 detection by GC, and kinetic isotope effect reveal the mechanism of this CoCl2-catalyzed reaction to be via ADC. Furthermore, kinetic experiments and Hammett analysis with variation in the nature of substituents over the aniline ring reveal the insight into the reaction mechanism with different substituents.

Robust late-stage benzylic C(sp3)–H aminations by using transition metal-free photoredox catalysis

Herein we report a transition metal-free approach for the regioselective functionalization of benzylic C(sp3)H bonds in the presence of various heterocyclic amines as nucleophiles. This straightforward and general route has provided various benzylic amines, including twelve pharmaceutically relevant compounds.

Sulfate radical anion-induced benzylic oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines.

A mild, operationally convenient, and practical method for the synthesis of synthetically useful N-arylsulfonylimines from N-(arylsulfonyl)benzylamines using K2S2O8 in the presence of pyridine as a base is reported herein. In addition, a "one-pot" tandem synthesis of pharmaceutically relevant N-heterocycles by the reaction of N-arylsulfonylimines, generated in situ with ortho-substituted anilines is also reported. The key features of the protocol include the use of a green oxidant, a short reaction time (30 min), chromatography-free isolation, scalability, and economical, delivering N-arylsulfonylimines in excellent yields of up to 96%. While the oxidation of N-aryl(benzyl)amines to N-arylimines using K2S2O8 is reported to be problematic, the oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines using K2S2O8 has been achieved for the first time. The dual role of the sulfate radical anion (SO4·-), including hydrogen atom abstraction (HAT) and single electron transfer (SET), is proposed to be involved in the plausible reaction mechanism.

Electrochemical Oxidative C-H Amination through a Ritter-Type Reaction.

A straightforward strategy for direct benzylic C-H bond amination via an electrochemical Ritter-type reaction is developed. The reaction demonstrates simpler and milder reaction conditions over the existing methods without extra mediator. Moderate to excellent yields up to 94% of the desired amide products were obtained with a broad substrate scope. The removal of the Ac group by a simple step can afford NH-free benzylic amines, providing a suitable approach for the late-stage functionalization of bioactive molecules.

Direct Cyclopalladation of Fluorinated Benzyl Amines by Pd3(OAc)6: The Coexistence of Multinuclear Pdn Reaction Pathways Highlights the Importance of Pd Speciation in C-H Bond Activation.

Palladacycles are key intermediates in catalytic C-H bond functionalization reactions and important precatalysts for cross-couplings. It is commonly believed that palladacycle formation occurs through the reaction of a substrate bearing a C-H bond ortho to a suitable metal-directing group for interaction with, typically, mononuclear "Pd(OAc)2" species, with cyclopalladation liberating acetic acid as the side product. In this study, we show that N,N-dimethyl-fluoro-benzyl amines, which can be cyclopalladated either ortho or para to fluorine affording two regioisomeric products, can occur by a direct reaction of Pd3(OAc)6, proceeding via higher-order cyclopalladated intermediates. Regioselectivity is altered subtly depending on the ratio of substrate:Pd3(OAc)6 and the solvent used. Our findings are important when considering mechanisms of Pd-mediated reactions involving the intermediacy of palladacycles, of particular relevance in catalytic C-H bond functionalization chemistry.

Green and efficient synthesis of primary amine from nitrile catalyzed by Pd-Ni oxide nanocluster

The selective hydrogenation of nitrile represents an atom-economical and reliable method to synthesize primary amine, a privileged compound in chemistry, biology, and medicine. However, this approach often displays severe selectivity issues, and additives or reducing agents are generally required to solve this problem. In this work, we aim to synthesize primary amine on a green catalytic system and probe into the catalytic mechanism of Pd-Ni interaction using benzonitrile (BN) as a model compound. The nitrile hydrogenation reaction was catalyzed by bimetallic Pd-Ni oxide nanospecies confined in Silicalite‑1 (S-1) zeolite using H2 as hydrogen donor without any additive which was environmentally friendly and economic. A 92% yield of benzylamine (BA) was achieved on the Pd0.6Ni@S-1 catalyst with a turnover number (TON) of 1667, and such BA yield was still maintained in upscaling experiment. Detailed characterizations shed light on the mechanism of the extraordinary performance of Pd-Ni oxide nanospecies on base-free nitrile hydrogenation.

Enhanced Photocatalytic Coupling of Benzylamine to N-Benzylidene Benzylamine over the Organic-Inorganic Composites F70-TiO2 Based on Fullerenes Derivatives and TiO2.

The organic-inorganic composites F70-TiO2, based on fullerene with carboxyl group derivatives and TiO2 semiconductor, have been designed and constructed to become an optical-functional photocatalyst via the facile sol-gel method. The composite photocatalyst obtained shows excellent photocatalytic activity for the high-efficiency conversion of benzylamine (BA) to N-benzylidene benzylamine (NBBA) with air pressure at a normal temperature under visible light irradiation. By optimizing the composition, the composites with the 1:15 mass ratio of F70 and TiO2, denoted as F70-TiO2(1:15), demonstrated the highest reaction efficiency for benzylamine (>98% conversion) to N-benzylidene benzylamine (>93% selectivity) in this study. However, pure TiO2 and fullerene derivatives (F70) exhibit decreased conversion (56.3% and 89.7%, respectively) and selectivity (83.8% and 86.0%, respectively). The UV-vis diffuse reflectance spectra (DRS) and Mott-Schottky experiment's results indicate that the introduction of fullerene derivatives into anatase TiO2 would greatly broaden the visible light response range and adjust the energy band positions of the composites, enhancing the sunlight utilization and promoting the photogenerated charge (e--h+) separation and transfer. Specifically, a series of results on the in situ EPR tests and the photo-electrophysical experiment indicate that the separated charges from the hybrid could effectively activate benzylamine and O2 to accelerate the formation of active intermediates, and then couple with free BA molecules to form the desired production of N-BBA. The effective combination, on a molecular scale, between fullerene and titanium dioxide has provided a profound understanding of the photocatalysis mechanism. This work elaborates and makes clear the relationship between the structure and the performance of functional photocatalysts.

A Universal Room‐Temperature Approach to Large‐Area Continuous COFs Film for Photocatalytic Coupling of Amines

AbstractLarge‐area continuous covalent organic frameworks (COFs) film is highly desirable for the large‐scale continuous selective photocatalytic coupling of benzylamine (BA); however, traditional synthetic methods for preparing COFs films still suffer from the issues of harsh reaction condition, film breakage, and high energy‐consumption. Herein, a room‐temperature strategy is reported for making large‐area continuous imine‐based COFs film through the “infiltration‐reaction‐assembly” mechanism, demonstrating that such strategy is quite universal for making four types of large‐area COFs films. The as‐made PyTTA‐TPA (PyTTA: 1，3，6，8‐tetrakis(4‐aminophenyl)pyrene, TPA: p‐benzaldehyde) COFs film exhibits excellent catalytic performance for selective photocatalytic coupling of benzylamine (BA) with a high conversion rate of 98.2% and high selectivity of 97% in 3 h, which is the best photocatalytic performance in all reported photocatalysts. In addition, the as‐made COFs film is quite general for achieving photocatalytic coupling of other amine derivatives with outstanding photocatalytic performance of ≈100% conversion rate. Overall, this work brings a significant development for the room‐temperature synthesis of large‐area continuous COFs film to photocatalytic reaction.

Detection of trimethylamine (TMA) gas using mixed shape cobalt doped ZnO nanostructure

Mixed shape cobalt (Co) doped ZnO nanostructures was synthesize using hydrothermal method with variable amount (0, 5 and 15%). The synthesized nanostructures were found to be selective towards trimethyl amine (TMA) sensing. The impact of doping on structural, optical, thermal stability, morphology and shape of Co doped ZnO nanostructures were studied using XRD, FT-IR, XPS, UV–Visible, HR-TEM, SAED, FESEM and EDS. The doping concentration was optimized for maximal gas response. ZnO and Co doped ZnO nanostructures were used to study TMA sensing at various temperatures (RT, 50, 75, 100, 125 °C) and found to be optimal at 100 °C for maximal gas response of TMA gas (50 ppm). ZnO and Co doped ZnO nanostructures were exposed to various amines and found to be more selective towards sensing of TMA. Moreover, the gas sensing study was carried out at different humidity rates (11, 32, 51, 63 and 84%) using variable saturated solutions. Co doped ZnO (15%) shows maximum response (86.1%) as compared to undoped (ZnO NPs) and doped (5%). The response and recovery time was recorded to be 19.4 and 15.5 s for 50 ppm of TMA gas. As the concentration of TMA gas increases from 10 to 100 ppm the gas sensing response increases. TMA gas shows enhanced selectivity towards mixed shape Co doped ZnO as compared to the other gases (benzyl amine, diphenyl amine, dimethyl amine, n-butyl amine, aniline, p-phenylene diamines, o-phenylene diamines, m-phenylene diamines and allyl amine gas). The reproducibility study of Co doped ZnO was performed for 70 days.

Organic Chain Length Effect on Trap States of Lead Halide Perovskite Scintillators

Scintillators fabricated from organic–inorganic layered perovskites have attracted wide attention due to their excellent properties, including fast decay times, superior light yield, and high exciton binding energy. In relation to their optoelectronic properties, hybrid organic–inorganic perovskites are known for their tunability, which could be manipulated by modifying the organic cations. In this study, we investigate the optical and scintillation properties of lead halide perovskites A2PbBr4, where A vary from amylammonium (AA), hexylammonium (HA), octylammonium (OA), and benzylammonium (BZA) organic ligands. Photoluminescence (PL) spectra display dual peaks due to surface and bulk trap states contributions, while fast average decay times from time-resolved photoluminescence (TRPL) for all samples are within the range of 0.69 ± 0.11–0.99 ± 0.13 ns. The optical band gap of these hybrid perovskites is within ∼3 eV range, which fulfill the criteria of promising scintillators. Radioluminescence (RL) spectra show negative thermal quenching behavior (NTQ) in all samples, with the AA2PbBr4 peak intensity appearing at relatively lower temperature compared to other samples. Thermoluminescence (TL) measurement reveals trap-free states in AA2PbBr4, while other samples possess shallow traps (<40 meV) as well as low trap density, which is beneficial for fast-decay scintillators, X-ray detection and energy conversion for solar cells. Overall, our results demonstrate that the extension of linear organic chains in lead-based perovskite is a deterministic strategy for a fast response hybrid-based scintillator to date.

Copper-Catalyzed Synthesis of 3-Aryl-9H-imidazo[1,5-a]indol-9-ones Using Oxygen as the Sole Oxidant.

A three-component strategy was developed for 3-phenyl-9H-imidazo[1,5-a]indol-9-one preparation from indole-2-carboxaldehydes, aromatic aldehydes, and ammonium acetate under copper catalysis conditions. In this process, a new five-membered ring was formed and the C3 position in the indole substrate was selectively oxidized into a ketone skeleton using oxygen as the sole oxidant and ammonium acetate as the nitrogen source. Furthermore, same products also could be achieved from indole-2-carboxaldehydes and benzyl amines under similar reaction conditions.

Harnessing Sulfur(VI) Fluoride Exchange Click Chemistry and Photocatalysis for Deaminative Benzylic Arylation.

While among the most common functional handles present in organic molecules, amines are a widely underutilized linchpin for C-C bond formation. To facilitate C-N bond cleavage, large activating groups are typically used but result in the generation of stoichiometric amounts of organic waste. Herein, we report an atom-economic activation of benzylic primary amines relying on the Sulfur(VI) Fluoride Exchange (SuFEx) click chemistry and the aza-Ramberg-Bäcklund reaction. This two-step sequence allows the high-yielding generation of 1,2-dialkyldiazenes from primary amines via loss of SO2. Excitation of the diazenes with blue light and an Ir photocatalyst affords radical pairs upon expulsion of N2, which can be coaxed into the formation of C(sp3)-C(sp2) bonds upon diffusion and capture by a Ni catalyst. This arylative strategy relying on a traceless click approach was harnessed in a variety of examples and its mechanism was investigated.

Investigation of influence of electrical field and solution of the surface-active substance (SAS) on water flood oil recovery factor

Influence of the electrical current fields and various type solutions of the surface-active substances on an interfacial tension, adsorption, desorption and on oil recovery factor from heavily clay porous medium has been investigated in the article. Nonionic alfenol, cation-active DMABACH (Dimethyl Alkyl Benzyl Ammonium Chloride) and anion-active sulfonic acid have been used as SAS. Quartz sand and rock from surface exposure of Kirmakian Suite (KS) of Balakhany field are as an adsorbent. It was revealed that direct and alternating current at 50 and 100 V through solutions of different type of SAS doesn’t practically influence on their interfacial tension on the boundary of nonpolar hydrocarbon liquid. Direct and alternating current through the porous medium containing clays and carbonates doesn’t influence on value of dynamic adsorption of nonionic SAS but promotes a decrease of their desorption from the rocks surface. It was determined that shared use of the direct-current field and solution of nonionic surface-active substance in comparison with mineralized water doesn’t practically influence on value of the oil recovery factor due to high adsorption of its molecules on surface of the heavily clay rock of Kirmakian suite. The use of direct current at 100 V considerably allowed (up to 23 %) to increase the Kirmakian oil recovery factor by the stratal alkaline water

Ru(bpy)3]2+-functionalized polydopamine-coated polyurethane foam as an easily reusable macroscopic heterogeneous catalyst for visible-light photocatalysis

An easy-to-handle, highly reusable and efficient [Ru(bpy)3]2+-based heterogeneous photocatalyst was obtained by post-functionalization of a polydopamine-coated open cell polyurethane foam (PDA@PUF) via a silanization process of the mussel-inspired adhesive layer with 3-(triethoxysilyl)propan-1-amine (APTES), followed by an EDC-mediated coupling with [2,2′-bipyridine]-4-carboxylic acid and further complexation with [Ru(bpy)2Cl2] (bpy = 2,2′-bypyridine). The successful covalent grafting of APTES on the PDA layer of PUF and functionalization all over the foam surface with [Ru(bpy)3]2+ was suggested by 29Si CP-MAS NMR, XPS, ICP-AES and SEM-EDX. The macroscopic photocatalyst proved effective in model benzylic amine homocouplings and cross dehydrogenative couplings under visible-light irradiation and molecular oxygen, showing good functional group tolerance and excellent reusability in an easy-to-carry “dip-and-play” mode for at least six runs. Impressively, an improvement of the catalytic performances was even observed in both reactions, which most likely results from a modification of the uppermost layer of polydopamine throughout the successive cycles that renders the photocatalyst more accessible.