High performance of nitrogen-doped carbon-supported cobalt catalyst for the mild and selective synthesis of primary amines

A nitrogen-doped carbon-supported Co catalyst (Co/N-C-800) was discovered to be highly active for the reductive amination of carbonyl compounds with NH₃ and the hydrogenation of nitriles into primary amines using H₂ as the hydrogen source. Structurally diverse carbonyl compounds were selectively transformed into primary amines with good to excellent yields (82.8–99.6%) under mild conditions. The Co/N-C-800 catalyst showed comparable or better catalytic performance than the reported noble metal catalysts. The Co/N-C-800 catalyst also showed high activity for the hydrogenation of nitriles, affording the corresponding primary amines with high yields (81.7–99.0%). An overall reaction mechanism is proposed for the reductive amination of benzaldehyde and the hydrogenation of benzonitrile, which involves the same intermediates of phenylmethanimine and N-benzylidenebenzylamine.     

Synthesis of N-Alkylimino-1,2-di(9-carbazolyl)ethanes-Evidence for the Mechanism of the Reaction of Dichloroacetylene with Primary Amines

Dichloroacetylene (C₂Cl₂) reacts with carbazole and primary amines under phase-transfer catalytic (PTC) conditions to give 1-N-alkylimino-1,2-di(9-carbazolyl)ethanes (I) and 9-((E)-1,2-dichlorovinyl)carbazole (II) in one-step synthesis. Compounds I are formed from the addition of amines to the triple bond of C₂Cl₂ followed by reactions with carbazole.     

One‐Pot Synthesis and Hydroxylaminolysis of Asymmetrical Acyclic Nitrones

Abstract

Aromatic aldehydes 1 were reductively aminated to the corresponding secondary amines 2 using NaBH₄ in methanol in good yields. Amines 2 were oxidized with H₂O₂‐WO₄ ^2? regioselectively to nitrones 3, the structures of which were easily determined by reacting them with hydroxylamine hydrochloride as well as by spectral means. The products of hydroxylaminolysis in ether proved to be the corresponding benzaldehyde oximes 4 and benzyl or methyl hydroxylamine hydrochlorides 5.     

Sterically-Hindered Amines for Acid-Gas Absorption

Abstract

This paper reviews sterlcally-hindered amines for removal of add gases such as CO₂ and H₂S from gaseous streams. Steric hindrance of amines reduces carbamate stability. Moderately hindered amines are characterized by high rates of CO₂ absorption and high capacities for CO₂. The moderately hindered amine in use with organic solvent has considerably higher capacity than the conventional amine-solvent system for simultaneous removal of CO₂and H₂S from synthesis gas and natural gas. A severely-hindered-amine absorbent, characterized by a very low rate of CO₂absorption, has much higher capacity and selectivity than the current industry standard, methyldiethanolamine, for selective removal of H₂S from CO₂-containing streams. Use of hindered amines represents new advances in gas treating. Hindered amines save energy and capital in gas treating significantly. In addition, hindered amines used commercially have much better stability than conventional amines. As of today, fourteen commercial plants use hindered amines.     

Spontaneous Thiono-Thiolo Isomerization of Thiono-Phosphates. Does it Appear without Impurities?

Abstract

Thiono-thiolo isomerization of 0-alkyl esters of thiophosphoric acids to corresponding S-alkyl isomers has been extensively studied because of high biological acivity of both esters. Such an isomerization proceeding without other reactants initially added is called thermal isomerization. Kinetic studies of this process allow to distinguish between reaction pathways of methyl esters A₂P(S)OMe leading only to S-methyl esters and of diesters AP(S)(OMe)₂, which give also other products. It is well known that the isomerization can be effected by organic bases (amines, phosphines), corresponding alkylonium thiophosphates, and protic acids. We decided to investigate the kinetics of thermal isomerization in solutions, to examine the influence of impurities of reactants or solvents for thiophosphates studied up to now appear to be not thoroughly purified. O,O-Diphenyl-0-methylthiophosphate, 5,5-dimethyl-2-methoxy-2-thio-l,3,2-dioxaphos-phosphorinane and O,O-dimethyl-O-(4-nitro)phenylthiophosphate as model reactants and benzonitrile or 1-methylnaphtalene as solvents were chosen. We have found that the observed first-order rate constants k of the isomerization reaction significantly decreases (even 1000 times) with improving the purity of either the reactant or the solvent. The k values we could obtained may be considered to be the rate constant of either the thermal isomerization or the isomerization caused by residual impurities. For all the thiono-phosphate studied the activation energies of the thermal isomerization and the isomerization reaction with corresponding tetramethylammonium thiophosphates are practically the same. We believe that our findings may be of significant importance against the spontaneous isomerization of the thionophosphates studied.     

A convenient synthesis of t-butyldimethylsilyl protected cyanohydrins

A simple high yielding procedure is described for the direct conversion of aldehydes to t-butyldimethylsilyl (TBS) protected cyanohydrins using TBSCl, KCN and ZnI₂.     

Zur Stereochemie der Vitamin D3-Epoxide Röntgenstrukturanalyse einer 5,6-7,8-Diepoxidverbindung

Epoxidation of vitamin D₃ with benzonitrile ¦H₂O₂¦ KHCO₃ (Payne's reagent) yields exclusively the 5,6-mono-oxirane2. Further epoxidation with the same reagent gives the 5,6-7,8-bisepoxide3 a. Its stereochemistry and therefore the stereochemistry of2 was established by single crystal X-ray analysis of thep-Brbenzoate3b. Thereby for the first time a directive effect of a homoallylic hydroxyl group during thePayne-epoxidation was established.

Herrn Prof.Mihailovic (Universität Belgrad) mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Molecular Structure and Solution Behavior of a Benzonitrile Ligated Silver(I) Complex [Ag(PhCN)2][B(C6F5)4]

The bis(benzonitrile) complex [Ag(PhCN)₂][B(C₆F₅)₄] is synthesized from its tetra(acetonitrile) ligated congener. X‐ray diffraction studies were conducted to compare the bond lengths and angles of the complex in regard with those of other nitrile ligated silver cations with weakly coordinating anions. Vibrational spectra of the solid complex and in (concentrated) benzonitrile solution reveal differences in the strength of benzonitrile‐silver ion interactions.     

A 2-D tetrazole-based Zn(II) coordination polymer: crystal structure,dielectric constant,and luminescence

A tetrazole-based Zn(II) coordination polymer, [Zn(TMPT)₂] _n (1) (TMPT?=?5-(4-((1H-1,2,4-triazol-1-yl)methyl)phenyl)-2H-tetrazole), was synthesized by in situ reaction of 4-((1H-1,2,4-triazol-1-yl)methyl)benzonitrile, Zn(NO₃)_2?·?6H₂O, and NaN₃ under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Complex 1 contains π–π stacking interactions between tetrazole rings and phenyl rings of the 2-D ordered layered structural framework, which contribute to the dielectric response. In addition, 1 was demonstrated to display strong blue fluorescence emissions in the solid state at room temperature.     

Viscosity of Aqueous Solutions of n-butylamine,sec-butylamine and tert-butylamine

Abstract

Viscosities of the systems, water (W) + n-butylamine (NBA), W + sec-butylamine (SBA) and W + tert-butylamine (TBA) have been measured in the temperature range 298.15–323.15K. The viscosities (η) and excess viscosities (η^E) have been plotted against mole fraction of amines (X ₂). On addition of amines to water, viscosities first increase rapidly, then pass through maxima at 0.2 mole fraction of amines and then decline continuously as the addition of amines is continued. η^E show large positive values, with maxima also at 0.2 mole fraction of amines. The maxima of the curves of η and η^E vs. mole fraction of butylamines follow the order, W + TBA > W + SBA > W + NBA. The ascending part of the η vs. X ₂ curves in the water-rich region is explained by the hydrophobic hydration caused by the hydrocarbon tails and the hydrophilic effect due to — NH₂ group of amines. Following the maxima, amine - amine association is preferred, which accounts for the steady decrease of viscosity up to the pure state of amines.     

Studies on Pyrazine Derivatives,XLV: Synthesis,Reactions, and Tuberculostatic Activity of N-Methyl-N′-(pyrazine-2-carbonyl)-hydrazinecarbodithioic Acid Methyl Ester

Methyldithiocarbonyl derivative 2 of pyrazine-2-carboxylic acid N′-methyl-hydrazide 1 was synthesized by methylation of CS₂ adduct. Benzylamine caused the decomposition of compound 2 to pyrazine-2-carboxylic acid benzylamide 5 and 1,3-dibenzylthiourea 6. N-methyl-N′-(pyrazine-2-carbonyl)-hydrazinecarbodithioic acid methyl ester 2 were evidenced to cyclize to 3-methyl-5-pyrazin-2-yl-3H-[1, 3, 4]oxadiazole-2-thione 8 in the presence of triethylamine. In the reactions with secondary amines such as morpholine, pyrrolidine and phenylpiperazine pyrazinoyl derivatives (9–11) of thiosemicarbazide were obtained. Hydrazine, methylhydrazine, aminoalcohols, and N-alkylamino-substituted cyclic amines reacted with cyclization to 4-substituted 1,2,4-triazole-3-thiones 12, 13, and 18–22. Synthesized compounds exhibited low tuberculostatic activity in vitro (MIC 50–100 μg/mL).     

Aminophosphine ligands: synthesis,coordination chemistry,and activity of their palladium(II) complexes in Heck and Suzuki cross-coupling reactions

The reaction of 4-aminodiphenylamine or 2-aminofluorene with two equivalents of PPh₂Cl in the presence of Et₃N gives new bis(diphenylphosphino)amines N,N-bis(diphenylphosphino)-4-aminodiphenylamine 1 and N,N-bis(diphenylphosphino)-2-aminofluorene 2 in good yields. Oxidation of 1 or 2 with hydrogen peroxide, elemental sulfur or gray selenium affords the corresponding chalcogen derivatives. The palladium and platinum complexes of these P–N–P donor ligands were prepared by the reaction of the bis(phosphino)amines with MCl₂(cod) (M = Pd or Pt, cod = cycloocta-1,5-diene). All the new compounds have been characterized by analytical and spectroscopic methods, including ¹H-³¹P NMR, ¹H-¹³C HETCOR, or ¹H-¹H COSY correlation experiments. The Pd(II) complexes were investigated as catalysts in the Suzuki and Heck reactions; both showed good catalytic activity affording high yields of the desired products.     

Exciton absorption and intramolecular Penning ionisation in small molecular clusters I: (N2O)n and C6H5CN·(N2O)n

Photoionisation efficiency (PIE)-spectra are measured for small (N₂O)_n-clusters,n=2...8, using synchrotron radiation from the electron storage ring BESSY at Berlin. Ionisation thresholds are reported. Resonances in the wavelength-range 97...100 nm forn>2 are attributed to exciton absorption with N₂O-Rydberg levels, series I and II parentage. This interpretation is supported by measurements of the PIE of mixed benzonitrile · (N₂O)_n clusters where benzonitrile serves as a monitor for photon absorption in N₂O at energies above the ionisation limit of benzonitrile.     

Synthesis of β-Amino-α,α-dichloro Sulfones from Vinyl Sulfones

β-amino-α,α-dichloro sulfones 3 are prepared by the reaction of vinyl sulfone 1 with primary or secondary amines 2in the presence of CCI₄ and NaH.     

2,4-DINITROPHENYLHYDROXYLAMINE: AN EFFICIENT AND MORE GENERAL REAGENT FOR IRON-CATALYZED ALLYLIC AMINATION

2,4-Dinitrophenylhydroxylamine (1) is an efficient reagent for the iron-catalyzed regioselective allylic amination of olefins. Moderate to excellent yields of N-DNP-N-allyl amines (2) are obtained resulting from introduction of the N-DNP group at the less substituted vinylic carbon with accompanying double bond transposition. N-alkylation of 2 and subsequent treatment with MeNH₂ affords secondary N-alkyl-N-allyl amines (5) in good overall yield.     

Selected Reaction of (Z)-Dimethyl α-(Bromomethyl) Fumarate with Secondary Amines

Regioselective reaction of (Z)-dimethyl α-(bromomethyl) fumarate 2 with bulky secondary amines in ether as solvent at room temperature, leads exclusively to the rearranged substitution α-(functional alkyl amino) acrylic esters 4a-i in high yields. The less and more bulky amine gives rise respectively to the two successive (S_N2′) and (S_N2) substitution derivatives 5j,k and 51.     

Unmasking the Action of Phosphinous Acid Ligands in Nitrile Hydration Reactions Catalyzed by Arene–Ruthenium(II) Complexes

The catalytic hydration of benzonitrile and acetonitrile has been studied by employing different arene–ruthenium(II) complexes with phosphinous (PR₂OH) and phosphorous acid (P(OR)₂OH) ligands as catalysts. Marked differences in activity were found, depending on the nature of both the P‐donor and η⁶‐coordinated arene ligand. Faster transformations were always observed with the phosphinous acids. DFT computations unveiled the intriguing mechanism of acetonitrile hydration catalyzed by these arene–ruthenium(II) complexes. The process starts with attack on the nitrile carbon atom of the hydroxyl group of the P‐donor ligand instead of on a solvent water molecule, as previously suggested. The experimental results presented herein for acetonitrile and benzonitrile hydration catalyzed by different arene–ruthenium(II) complexes could be rationalized in terms of such a mechanism.     

A Rational Approach Towards Determination of Optical Ionicity and Non-covalent Interactions in Fullerene-Calix[4]arene Host-Guest Complexes

The present article reports the host-guest complexation of a calix[4]arene derivative, namely 4-iso-propyl-calix[4]arene (1), with fullerenes (both C₆₀ and C₇₀) in toluene and benzonitrile solutions. It is observed that the charge-transfer (CT) absorption bands are located in the ground state for the C₆₀ and C₇₀ complexes of 1. By utilizing the CT absorption bands, various important physicochemical parameters like the oscillator strength, resonance energy, transition dipole moment, electronic coupling element and solvent reorganization energies have been estimated for the C₆₀-1 and C₇₀-1 complexes. The CT transition energy is very helpful for determining the vertical ionization potential of 1 in solution. Jobs method of continuous variation was used to establish 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds C₇₀ preferentially compared to C₆₀ as obtained from binding constant (K) data. The effect of solvent on the complexation of fullerenes (C₆₀ and C₇₀) with 1 is clearly observed from the trend in the K values: in toluene and whereas in benzonitrile, and . Molecular mechanics force field (MMMF) calculations reveal fascinating features regarding the binding pattern of fullerenes towards 1 in vacuo in terms of enthalpy of formation. MMMF calculations establish that during C₇₀-1 complexation, C₇₀ is directed in an end-on manner rather than the traditional side-on pattern.     

Deamination of Quaternary Hydrazinium Halides. A Convenient Synthesis of Tertiary Amines

Abstract

Deamination of quaternary hydrazinium salts [(CH₃)₂R'NNH₂ X^?] with nitrous acid provides a convenient route to tertiary amines.     

Mono- and dinuclear metallacyclic complexes of Pt(II) synthesized from some eugenol derivatives

The complexes K[PtCl₃(Meug)] (1; Meug = methyleugenol), K[PtCl₃(Meteug)] (2; Meteug = methyl eugenoxyacetate), and K[PtCl₃(Eteug)] (3; Eteug = ethyl eugenoxyacetate) reacted with AgNO₃, SnCl₂, KOH, or ethanol–water solutions to lose one aryl proton and form dinuclear metallacyclic complexes Pt₂Cl₂(Meug-1H)₂ (4), Pt₂Cl₂(Meteug-1H)₂ (5), and Pt₂Cl₂(Eteug-1H)₂ (6), respectively. Complexes 4–6 reacted with aliphatic, aromatic, and heterocyclic amines to give various mononuclear metallacyclic platinum complexes 7–15. ¹H NMR spectra showed that in 4–15 Meug, Meteug, and Eteug are bound with Pt(II) both at the benzene carbon and at the ethylenic double bond of the side chain. NOESY spectra and single-crystal X-ray diffraction indicated that in 7–15 the amines are in cis-position with respect to the ethylenic double bond.