Selectivity For Primary Amines Research Articles

Boosting primary amines renewable tandem synthesis via defect engineering of NiCo alloy

AbstractReductive amination of biomass aldehydes is a vital process to synthesize chemical intermediates primary amine, but the selectivity is severely compromised by the self‐condensation of highly reactive imine intermediates. Herein, we proposed a solution by manipulating the adsorption configuration of secondary imine via defect engineering. Specifically, a gradient reduction strategy was used to adjust the driving force of NiCo alloy crystallization, thus motivating the formation of metal vacancy clusters. The primary amine selectivity was raised from 70.9% to 95.1% with defect concentration increased from 36.1% to 42.5% on catalysts. In situ fourier transform infrared spectroscopy (FTIR) and density functional theory demonstrated metal vacancy clusters induced remarkable NiCo electron transfer, which strengthened electronic coupling between secondary imine with catalyst, resulting in a flat configuration that was conducive to CN bond breakage to guarantee smooth conversion into primary amines. This catalyst exhibited potential real‐life application prospects for its low cost, universality in reductive amination of various aldehydes, and long‐life reusability.

Analysis of thermodynamics, kinetics, and reaction pathways in the amination of secondary alcohols over Ru/SiO2

This work considers the Ru-mediated amination of secondary alcohols with ammonia in vapor and liquid media. We map thermodynamic constraints, and we probe the impacts of species partial pressure, residence time, and reaction temperature on rate, selectivity, and catalyst stability. Alcohol amination consumes no H2, and H2 has no significant impact on amination kinetics; however, operating under H2 benefits Ru stability. Primary amine selectivity increases with ammonia pressure and alcohol conversion, and the latter observation is consistent with the formation of primary amines through a network of sequential reactions. Unfortunately, primary amines are susceptible to secondary deamination to form hydrocarbons. As is typical of processes that seek to isolate a reactive intermediate, the main selectivity challenge here is identifying residence times that are long enough to accumulate high substrate conversion but short enough to avoid secondary deamination. In general, moderate residence times will maximize the production of primary amines. Insights extend across a broad substrate scope, and we observe 70 – 90% yield of primary amines from linear, cyclic, and heterocyclic alcohols. That said, heterocyclic alcohols appear susceptible to product inhibition, so achieving high conversions requires longer residence times and/or increased ammonia pressures.

A versatile AIE fluorogen with selective reactivity to primary amines for monitoring amination, protein labeling, and mitochondrial staining

AbstractSpecific bioconjugation for native primary amines is highly valuable for both chemistry and biomedical research. Despite all the efforts, scientists lack a proper strategy to achieve high selectivity for primary amines, not to mention the requirement of fast response in real applications. Herein, we report a chromone‐based aggregation‐induced emission (AIE) fluorogen called CMVMN as a self‐reporting bioconjugation reagent for selective primary amine identification, and its applications for monitoring bioprocesses of amination and protein labeling. CMVMN is AIE‐active and capable of solid‐state sensing. Thus, its electrospun films are manufactured for visualization of amine diffusion and leakage process. CMVMN also shows good biocompatibility and potential mitochondria‐staining ability, which provides new insight for organelle‐staining probe design. Combined with its facile synthesis and good reversibility, CMVMN would not only show wide potential applications in biology, but also offer new possibilities for molecular engineering.

Primary amine synthesis by hydrogen-involving reactions over heterogeneous cobalt catalysts

Co/SiO2 exhibited high selectivity for primary amines in hydrogenation of nitriles and reductive amination of carbonyl compounds.

Synthesis, spectroscopic and computational evaluation of a xanthene-based fluorogenic derivatization reagent for the determination of primary amines

To detect an analyte, typically at the sub-nanomolar scale, extremely sensitive analytical tools are required. Fluorescence is the spectroscopy of choice to achieve such a level due to its non-invasive nature and efficiency in accurately probing the sub-nanomolar concentration range. Here, we report the design, synthesis and photophysical characterization of a fluorogenic derivatization reagent with exclusive selectivity for primary amines. This xanthene-based dye owns an exacerbated fluorogenic character making the derivatized amine absorbing in yellow and emitting in the vermilion edge. In addition to being fluorogenic, this derivatization method also has the crucial advantage of being chromogenic (colorless => fuchsia). Chemical quantum calculations give an insight into the dye's molecular properties, while the development of an LC analytical method provides proof of concept regarding its application for the analysis of primary amines in a complex matrix.

Selective hydrogenation of benzonitrile and its homologues to primary amines over platinum

Various supported precious metal (Pt, Rh, Ru, Ir) catalysts have been screened in the reduction of benzonitrile (BN), benzyl cyanide (BC) and 3-phenylpropionitrile (PPN) to benzylamine (BA), 2-phenylethylamine (PEA) and 3-phenylpropylamine (PPA), using our method for selective, heterogeneous, palladium-catalysed hydrogenation of nitriles to primary amines developed previously. A readily available platinum on carbon catalyst (10% Pt/C) afforded the best results obtaining complete conversion of nitriles, as well as comparatively high isolated yields (58–70%) and selectivities to primary amines (57–68%) under mild and optimized conditions [6 bar, 30 °C, two immiscible solvents (dichloromethane/water or toluene/water), acidic additives (NaH2PO4, (NH4)H2PO4 or H2SO4)]. Contrary to the typical high secondary amine selectivity of platinum, surprisingly, this Pt/C catalyst proved to be much more effective and selective in the formation of PEA and PPA than a Pd/C one applied earlier. To clear the divergences in the primary amine selectivity observed, quantum chemical calculations (DFT) were accomplished related to the adsorption interactions between the imine intermediates and platinum.

Intrinsic mechanism of active metal dependent primary amine selectivity in the reductive amination of carbonyl compounds

For the catalytic reductive amination of carbonyl compounds, the kind of active metal used is the most important factor determining the catalytic selectivity in heterogeneous catalysis systems. However, a detailed understanding of the intrinsic mechanism is still lacking. In this work, by evaluating the reductive amination of butyraldehyde and the hydrogenation reaction of secondary imine on various metal catalysts, the competitive hydrogenation reactions of primary imine and secondary imine are proven to be the key factors determining primary amine selectivity. DFT calculations verify that Co, Ni, and Ru, rather than Fe, Rh, Pd, and Pt, tend to show high primary amine selectivity in terms of adsorption energy and activation energy. It should be noted that the different stable adsorption modes of secondary imine on metal surfaces (C&N adsorption mode on Fe, Co, Ni, Ru, and Rh, and N adsorption mode on Pd and Pt) are key factors affecting these reaction characteristics. Moreover, microkinetic simulation proves that the coadsorption of NH3 improves primary amine selectivity on Co, Ni, and Ru surfaces. Combining the theoretical and experimental results, it is clearly verified that the active metal determines the catalytic selectivity of the primary amine by affecting the competitive hydrogenation reactions of the primary imine and secondary imine.

Heterogeneous Catalytic Hydrogenation of 3-Phenylpropionitrile over Palladium on Carbon.

A previously developed and industrially feasible process for selective, Pd-mediated, liquid-phase heterogeneous catalytic hydrogenation of nitriles to primary amines was extended to the reduction of 3-phenylpropionitrile (PPN) to 3-phenylpropylamine (PPA). PPN, which belongs to the homologous series of benzonitrile (BN) and benzyl cyanide (BC), was hydrogenated under mild reaction conditions (30–80 °C, 6 bar), over Pd/C, in two immiscible solvents (dichloromethane/water) and using acidic additives (NaH2PO4 and H2SO4). Although relatively high conversion (76%) was achieved, the selectivity to PPA (26%) and its isolated yield (20%) were lesser than those in the case of the hydrogenation of BN or BC reported earlier. However, the purity of PPA was >99% without using any purification method. Quantum chemical calculations using a density functional theory (DFT) method were performed to compare the adsorption interactions of the different imine intermediates on palladium, as well as to clarify the differences observed in the primary amine selectivity. PPA is a valuable intermediate for the synthesis of carboxypeptidase B enzyme inhibitors, antimuscarinic drugs, or potential anticancer agents in the pharmaceutical industry.

Fast super/subcritical fluid chromatographic enantioseparations on superficially porous particles bonded with broad selectivity chiral selectors relative to fully porous particles

Superficially porous particles (SPPs) have shown advantages in enantiomeric separations in HPLC by conserving selectivity while providing higher efficiency separations with significantly reduced analysis times. The question arises as to whether the same advantages can be found to the same extent in super/subcritical fluid chromatography. In this work, the low viscosity advantage of carbon dioxide/MeOH mixtures is coupled with high-efficiency 2.7 μm superficially porous particles for enantiomeric separations. Given the fact that the viscosity of the mobile phase is typically ten times lower than liquid mobile phases it is possible to use flow rates as high as 14 mL/min on 5 cm packed columns. Superficially porous particles (SPPs) were grafted with teicoplanin (TeicoShell), a chemically modified macrocyclic glycopeptide (NicoShell), vancomycin (VancoShell), and isopropyl derivatized cyclofructan-6 (LarihcShell-P). One hundred chiral analytes were separated in a very short time frame, as little as 0.2 min (13 s). Even shorter separations can be obtained with advances in SFC instrumentation. The LarihcShell-P is the only chiral crown ether-based selector which showed high selectivity for primary amines. The Teicoshell column offered unique separations for acidic and neutral analytes. The NicoShell and the VancoShell were useful in separating amine (secondary and tertiary) containing pharmaceutical drugs and controlled substances. By chemically modifying a macrocyclic glycopeptide (NicoShell) we report the first enantiomeric separation of nicotine under SFC conditions within 3 min with a resolution of >3. Additionally, van Deemter plots are constructed comparing the fully porous particles and superficially porous particles bonded with the same chiral selectors. In toto the SPP advantages also were found for SFC. However instrumental shortcomings involving extra column effects and pressure limitations need to be addressed by instrument manufacturers to realize the full advantages of SPPs and other smaller particle supports.

A ppm level Rh-based composite as an ecofriendly catalyst for transfer hydrogenation of nitriles: triple guarantee of selectivity for primary amines

A 49 ppm Rh catalyst selectively transforms nitriles into primary amines with economical HCOOH and exhibits a TOF value of 6803 h−1.

Supported Ni Catalyst for Liquid Phase Hydrogenation of Adiponitrile to 6-Aminocapronitrile and Hexamethyenediamine.

Supported Ni catalysts prepared under different conditions, for liquid phase hydrogenation of adiponitrile (ADN) to 6-aminocapronitrile (ACN) and hexamethyenediamine (HMD), were investigated. The highly reactive imine intermediate can form condensation byproducts with primary amine products (ACN and HMD), which decreased the yield coefficient of primary amines. The catalysts support, condition of catalyst preparation and dosage of additive were studied to improve the yield. A highly dispersed Ni/SiO2 catalyst prepared by the direct reduction of Ni(NO3)2/SiO2 suppressed the condensation reactions by promoting the hydrogenation of adsorbed imines, and it gave the improved hydrogenation activity of 0.63 mol·kgcat−1·min−1 and primary amine selectivity of 94% when NaOH was added into the reactor.

Liquid phase hydrogenation of adiponitrile over directly reduced Ni/SiO2 catalyst

Liquid phase hydrogenation of adiponitrile (ADN) to 6-aminocapronitrile (ACN) and hexamethylenediamine (HMD) was investigated on Ni/SiO2 catalysts prepared under different conditions. In this reaction, the highly reactive imine intermediate forms condensation byproducts by reacting with the primary amine products (ACN and HMD). A highly dispersed Ni/SiO2 catalyst prepared by the direct reduction of Ni(NO3)2/SiO2 was found to suppress the condensation reactions by promoting the hydrogenation of adsorbed imine, and it gave excellent hydrogenation activity and primary amine selectivity. Addition of NaOH increased the primary amine selectivity to 79% at the ADN conversion of 86%.

Pentacoordinated carboxylate π-allyl nickel complexes as key intermediates for the Ni-catalyzed direct amination of allylic alcohols.

Direct amination of allylic alcohols with primary and secondary amines catalyzed by a system made of [Ni(1,5-cyclooctadiene)2 ] and 1,1'-bis(diphenylphosphino)ferrocene was effectively enhanced by adding nBu4 NOAc and molecular sieves, affording the corresponding allyl amines in high yield with high monoallylation selectivity for primary amines and high regioselectivity for monosubstituted allylic alcohols. Such remarkable additive effects of nBu4 NOAc were elucidated by isolating and characterizing some nickel complexes, manifesting the key role of a charge neutral pentacoordinated η(3) -allyl acetate complex in the present system, in contrast to usual cationic tetracoordinated complexes earlier reported in allylic substitution reactions.

Reduction of Nitriles to Amines with H2 Catalyzed by Nonclassical Ruthenium Hydrides – Water‐Promoted Selectivity for Primary Amines and Mechanistic Investigations

AbstractCatalytic hydrogenation of nitriles to amines by nonclassical ruthenium hydride complexes derived from PNP pincer ligands is described. Aromatic as well as aliphatic nitriles are reduced to the corresponding primary amines. Hydrogen pressure influences the selectivity for the primary amines. The mechanism of nitrile reduction with nonclassical ruthenium hydride pincer complexes is investigated by DFT calculations. A catalytic cycle involving the coordination of nitrile trans to the pincer backbone after an initial hydride rearrangement at the ruthenium center, and the subsequent first transfer of the hydride ligand to the carbon center of the nitrile ligand is suggested as a possible reaction mechanism. Interestingly, the use of water as additive increases the selectivity for the primary amines and the rate of the reactions.

Plasma Deposition of Allylamine on Polymer Powders in a Fluidized Bed Reactor

AbstractSummary: Thin films of plasma‐polymerized allylamine (PPAA) have been deposited onto polyethylene powders (PE) and polystyrene (PS) beads by using a low‐pressure 13.56 MHz plasma in a fluidized bed reactor. Chemical derivatization using a set of three different blocking agents has allowed quantitative measurement of the relative percentages of primary, secondary, and tertiary amines. Under optimized conditions, it is possible to incorporate up to 110 nmol of amine groups per gram of powder and with a selectivity of 75% for primary amines. Moreover, our data clearly show that for films deposited at 10 W the selectivity for primary amines is at a maximum, but this is at the expense of resistance to washing. A power of 20 W corresponds to an optimum value since both the amount of primary amines and the degree of resistance of the coating to solvents reach maximum values.Distribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.imageDistribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.

Syngas reactions Part XV. Primary amine syntheses from olefins, syngas and ammonia

The selective preparation of aliphatic primary amines from an olefin, synthesis gas (CO/H 2), and ammonia has been developed involving the use of homogeneous catalysts comprising cobalt octacarbonyl, phosphine ligand, and an ether or acetamide solvent system. 1-Hexene oxoamination typically yields a mix of C 7 plus C 14 primary amine in 57% selectivity. Process parameter studies involving changes in [NH 3], [Co], P/Co molar ratios, H 2/CO ratios, etc. provide some insight into the mechanism of this multi-step synthesis and the practical limits (ca. 65%) to primary amine selectivity and yield.