A novel heterotricyclic assembly through intramolecular imino Diels-Alder reaction: synthesis of pyrrolo[3,4-b]quinolines

The synthesis of a series of hexahydropyrrolo[3,4-b]quinolines has been achieved in excellent yields by the reaction of aldimines derived from aromatic amines and N-prenylated aliphatic aldehydes in acetonitrile with InCl₃ as a catalyst in a short duration of time.     

Native amine-directed site-selective C(sp3)-H arylation of primary aliphatic amines with aryl iodides

Direct C(sp³)-H functionalization of N-unprotected aliphatic amines represents one of the most efficient and straightforward strategies for amine synthesis. Despite some recent progress in this field, the NH₂-directed γ-C(sp³)-H arylation of primary aliphatic amines except α-amino esters remained an unmet challenge. In this report, we established a simple and efficient method for site-selective C(sp³)-H arylation of primary aliphatic amines by aryl iodides. In the presence of only 5 mol% Pd(OAc)₂, a wide range of aliphatic amines including O-benzyl and O-silyl amino alcohols were arylated at γ- or δ-positions by aryl iodides containing a broad scope of functional groups. The synthetic application of this method had also been demonstrated by large-scale synthesis, the synthesis of a fingolimod analogue, and the conjugation with natural d-menthol and fluorescent 1,8-naphthalimide.     

Spectrofluorimetric determination of aliphatic amines using a new fluorigenic reagent: 2,6-dimethylquinoline-4-(N-succinimidyl)-formate

A new amino fluorescence probe, 2,6-dimethylquinoline-4-(N-succinimidyl) formate (DMQF-OSu) has been synthesized. Based on the selective reaction of DMQF-OSu with primary and secondary aliphatic amines to yield strong fluorescence, a new spectrofluorimetric method for the determination of total aliphatic amines has been developed. At λ_ex/λ_em=324.4/416 nm, the linear calibration range was 6×10⁻⁸-6×10⁻⁶ mol l⁻¹ with the detection limit (3σ) of 1.94×10⁻¹⁰ mol l⁻¹ for the determination of aliphatic amines in weak basic media. The proposed method has been applied to the determination of aliphatic amines in tap water and lake water with the recoveries of 99-104%. Compared with the reported methods, the method presented here is rapid, simple, sensitive and feasible.     

Gas-chromatographic determination of aliphatic amines in natural surface water and wastewater

A procedure was developed for the gas-chromatographic determination of aliphatic amines C₇–C₂₀ with prederivatization by N-methyl-bis(trifluoroacetamide), in the concentration range of natural surface water, to 10^?4-1 mg/L, and wastewater, to 10^?3-1 mg/L. The conditions were optimized for the extraction preconcentration of aliphatic amines with toluene from natural surface water and wastewater. The detection limit for aliphatic amines at a signal-to-noise ratio of 3: 1 was 50 ng/L.     

Effect of a carboxyl group on the chemiluminescent reaction of tris(2,2′-bipyridine)ruthenium(III) with aliphatic amines

The effect of a carboxyl group beside nitrogen of aliphatic amines on the tris(2,2′-bipyridine)ruthenium(III), Ru(bpy)₃³⁺, chemiluminescent reaction was examined. It has been shown that a carboxylate anion promotes the chemiluminescent reaction at a lower pH and then the aliphatic amines with this substituent can be sensitively detected compared with corresponding aliphatic amines without this substituent. Based on this finding, preliminary studies on simultaneous determination of 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid in human serum have been performed using isocratic reversed-phase ion-pair high-performance liquid chromatography (HPLC) with electrogenerated Ru(bpy)₃³⁺ chemiluminescent detection. The detection limits (signal-to-noise ratio of 3) with the proposed method were 3.0, 12, 2.7, 4.6, and 10 nM for 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid, respectively.     

Nucleophilic alkynylation of N-bis(trimethylsilyl)methyl aldimines

N-Bis(trimethylsilyl)methyl aldimines undergo nucleophilic addition reaction with premixed lithium alkynides/BF₃·OEt₂ to give moderate to good yields of N-bis(trimethylsilyl)methyl propargyl amines.     

1H 13C NMR investigation of E/Z-isomerization around CN bond in the trans-alkene-Pt(II)imine complexes of some ketimines and aldimines

Ketimines (K1, K2) and aldimines (A1, A2, and A3) were prepared from unsubstituted acetophenone and/or benzaldehyde and primary amines (i-PrNH₂, i-BuNH₂ and t-BuNH₂). These imines were reacted with Zeise’s salt (potassium ethenetrichloroplatinate(II)) to produce the respective complexes, namely, PtK1, PtK2, PtA1, PtA2, and PtA3. ¹H, ¹³C, and ¹⁹⁵Pt-chemical shifts of the ligands and their complexes were studied to investigate the nature and mode of isomerization around CN bond. The aldimines and their complexes were obtained as a single isomer. On the other hand, the ketimines and their complexes were obtained as a mixture of E/Z-isomers. It was found that the aldimine- and ketimine-platinum complexes undergo slow E/Z-isomerization in solution as evidenced from NMR spectra.     

Spectral and kinetic evidence for attack at coordinated phenanthroline in the reaction between aliphatic amines and transition metal complexes of 5-nitro-1,10-phenanthroline

Various transition metal complexes of 5-nitro-1,10-phenanthroline react with aliphatic amines in dipolar aprotic solvents to give deeply coloured species. The spectral changes, which can be reversed upon addition of acid or of the appropriate protonated amine, do not depend either on the nature of the metal and the ancillary ligands or on the geometry of the complexes; this has been taken as evidence that the colour forming process is due to a specific interaction of aliphatic amines with coordinated phenanthroline. While the rate of reaction of [Pt(5-NO₂phen)Cl₂] and [Pd(5-NO₂phen)Cl₂] with Br^?, which is known to displace Cl^? in the substrates, depends strongly on the nature of the central atom, the second order rate constant at 25°C being 3.2 × 10^?4 dm³mol^?1s^?1 and 1.35 dm³mol^?1s^?1 for the platinum and the palladium derivative respectively, the rate of reaction with n-propylamine has a comparable value for both substrates. This is further evidence that amines attack the coordinated phenanthroline, rather than the central atom. On the basis of the spectral features and the reaction stoicheiometry, the adducts of metal complexes of 5-NO₂phen and aliphatic amines are presumably Meisenheimer-like complexes.     

One-pot synthesis of α-aminophosphonates catalyzed by antimony trichloride adsorbed on alumina

SbCl₃ adsorbed on Al₂O₃ is found to be an efficient and recyclable catalyst in promoting three-component coupling reactions of aldehydes (aromatic and aliphatic), amines (aryl amines, aliphatic amines and esters of S-α-amino acids) and dialkylphosphites to afford the corresponding α-aminophosphonates in high yields. The ethyl ester of S-phenylalanine was observed to yield the corresponding α-aminophosphonate with S,S-diastereoisomer formed in dominance over the S,R-diastereoisomer.     

Polymerization of acrylamide photoinitiated by tris(2,2′‐bipyridine)ruthenium(II)–amine in aqueous solution: Effect of the amine structure

The photopolymerization of acrylamide (AA) initiated by the metallic complex tris(2,2′‐bipyridine)ruthenium(II) [Ru(bpy)₃⁺²] in the presence of aliphatic and aromatic amines as co‐initiators was investigated in aqueous solution. Aromatic amines, which are good quenchers of the emission of the metal‐to‐ligand‐charge‐transfer excited state of the complex, are more effective co‐initiators than those that do not quench the luminescence of Ru(bpy)₃⁺², such as aliphatic amines and aniline. Laser‐flash photolysis experiments show the presence of the reduced form of the complex, Ru(bpy)₃⁺¹, for all the amines investigated. For aliphatic amines, the yield of Ru(bpy)₃⁺¹ increases with temperature, and on the basis of these experiments, a metal‐centered excited state is proposed as the reactive intermediate in the reaction with these amines. The decay of the transient Ru(bpy)₃⁺¹ is faster in the presence of AA. This may be understood by an electron‐transfer process from Ru(bpy)₃⁺¹ to AA, regenerating Ru(bpy)₃⁺² and producing the radical anion of AA. It is proposed that this radical anion protonates in a fast process to give the neutral AA radical, initiating in this way the polymerization chain. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4265–4273, 2001     

Microdetermination of aliphatic amines and polyamines with cupric ion: Relationship between pK1 and half-complexation potential

The first equilibrium constant for the combination of ligand with cupric ion, K₁, is related to the half-complexation potential, E_HC, by log K₁ = a + b[E_HC]. The coefficients differ for n ? 2 and n ? 2, where n is the number of nitrogen atoms in the molecule. The correlation coefficients, r, based on data available from the literature were ?0.98. The equations can be used for estimating log K₁ of aliphatic amines. Successful titration of aliphatic amines vs cupric ion requires log K₁ ? 4 and an initial pH of a 10^?3M solution of ?9.     

Synthesis of molybdenum complexes containing η3-bonded trans-butadienyl ligands: crystal structure of[Mo(2,2′-bipyridine)(CO)2-

Reaction of Ph₄P[Mo(2,2′-bipyridine)Cl(CO₃] with 1,4-dichlorobut-2-yne in the presence of primary or secondary aliphatic amines gives high yields of neutral molybdenum complexes containing 2-substituted η³-bonded trans-butadienyl ligands. The crystal structure of the perfluorocarboxylate derivative [Mo(2,2′-bipyridine)(CO)₂(η³-CH₂C(CONHMe)CCH₂) (O₂CC₃F₇] has been determined.     

Alkyne as a spectator ligand for the nickel-catalyzed multicomponent connection reaction of diphenylzinc, 1,3-butadiene, aldehydes, and amines

Under nickel catalysis, in the presence of 3-hexyne, the aldimines of aromatic amines react with Ph2Zn and one molecule of butadiene to provide 1 exclusively, while the aldimines of aliphatic amines react with Ph2Zn and two molecules of butadiene to provide 2 exclusively, where 3-hexyne serves as a spectator ligand controlling the selective formation of 1 and 2.     

Charge transfer initiation of methylmethacrylate by isopropylamine

Methylmethacrylate (MMA) can be initiated by charge transfer complexes (i) formed by the interaction of aliphatic amines and MMA and (ii) formed by the interaction of aliphatic amines and carbon tetrachloride in a solvent like N-N dimethylformamide (DMF), dimethyl sulphoxide (DMSO) or chloroform. This paper reports the polymerization of MMA by isopropylamine (IPA) in the presence of CCl₄ in DMSO at 30. The rate of polymerization, R_p increases rapidly with CCl₄ up to a concentration of 0.25 mol l^?1 but, for a higher concentration, it is practically independent of the CCl₄ concentration. R_p is proportional to (IPA concentration)^{1 2} and to power of (MMA concentration)^1.30 when [CCl₄] ? [IPA]. The average rate constant, k, is 2.1 × 10^?6 l mol^{· 1} sec^{? 1}.     

Indium chloride catalyzed intramolecular cyclization of N-aryl imines: synthesis of pyrrolo[2,3-d]pyrimidine annulated tetrahydroquinoline derivatives

The intramolecular aza Diels-Alder cyclization reaction of aldimines derived from aromatic amines and N-prenyl/cinnamyl derivatives of pyrrolo[2,3-d]pyrimidine were efficiently catalyzed by InCl₃ to afford the corresponding tetrahydroquinoline derivatives in good yields.     

N-(Benzoyloxy)amines: an investigation of their thermal stability, synthesis, and incorporation into novel peptide constructs

A series of N-benzoyloxyamines were pyrolyzed and their decomposition temperatures correlated well with the amine architecture's ability to stabilize a N-centered radical. A variety of amine substrates were treated with a biphasic mixture of benzoyl peroxide (BPO), CH₂Cl₂ and an aqueous carbonate buffer (at pH 10.5). Primary and secondary amines were successfully N-benzoyloxylated in good yield. Tertiary amines and BPO gave low yields of the corresponding N-oxide and complex product mixtures, presumably via radical decomposition. Electron deficient amines (such as fluorinated aliphatic amines, α-aminoacids, α-aminoesters, and α-aminoamides) were not N-benzoyloxylated under these conditions. Instead, N-benzoylation was observed with the fluorinated amines and the reaction was sensitive to temperature and the pH of the aqueous medium. A one-pot-two-step synthesis of N^α-FMOC-l-Leu-N^β-(benzoyloxy)-β-alanine ethyl ester, a peptide containing both an α- and a novel β-amino acid framework, was also developed.     

Doubly charged ion mass spectra: VI—Amines

Doubly charged ion mass spectra of 22 amines (2–10 carbon atoms) were determined using an Hitachi RMU-7L double focusing mass spectrometer. Molecular ions were not observed in the spectra of aliphatic amines. The most intense product ion peaks in the spectra of lower molecular weight amines resulted from hydrogen elimination from the molecular ion; however, as amine molecular weight increased the largest peaks resulted from both hydrogen and heavy atom elimination from the molecular ion. Dominant ions in the doubly charged ion spectra of lower molecular weight aliphatic amines were from reactions of [C_nH₃N]²⁺ (n:=2, 3, 4) type ions. The spectra of higher molecular weight aliphatic amines spanned a wide mass range. Appearance energies for some of the more prominent ions were measured in the range from 25 to 49 eV. A geometry optimized quantum mechanical self-consistent field molecular orbital treatment was used to compute the energies and structural parameters of prominent ions in the doubly charged ion mass spectra.     

Rapid synthesis of tetrahydroquinolines by indium trichloride catalyzed mono- and bis-intramolecular imino Diels-Alder reactions

A rapid synthesis of mono- and bis-tetrahydropyrazolo[4′,3′:5,6]thiopyrano[4,3-b]quinolines has been achieved by the reaction of aldimines derived from aromatic amines and S-prenylated aldehydes in acetonitrile with InCl₃ as a catalyst, in excellent yields and short reaction times, under mild conditions.     

Determination and Identification of Primary Aliphatic Amines Using 4-(1H-Phenanthro[9,10-d]Imidazol-2-yl)Benzoic Acid as Novel Pre-Column Labeling Reagent by LC with Fluorescence Detection and Atmospheric Pressure Chemical Ionization Mass Spectroscopy

4-(1H-Phenanthro[9,10-d]imidazol-2-yl)benzoic acid (PIBA), a new amine-reactive fluorescent probe was synthesized and used as a pre-column derivatizing reagent for the determination of aliphatic amines from environmetal water samples. Derivatization was successfully carried out by a condensation reaction using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride as the dehydrant. Studies on derivatization conditions indicated that the condensation reaction proceeded rapidly and smoothly in the presence of pyridine. Amines were labeled with PIBA to give the corresponding sensitively fluorescent derivatives with an excitation maximum at λ _ex 260 nm and an emission maximum at λ _em 445 nm. Identification of derivatives was carried out by online APCI–MS–MS and showed an intense protonated molecular ion corresponding m/z [M + H]⁺ in the positive ion mode. Excellent linear responses were observed with coefficients of >0.9996. Detection limits were 6.7–27 fmol (at a signal-to-noise ratio of 3). The mean intra- and inter-assay precision for all amine levels were <2.79 and 3.85%, respectively. The established method for the determination of aliphatic amines from real water was satisfactory.     

Reactions of 3-cyanochromones with primary amines: structures of the products

Reactions of 3-cyanochromones with primary aromatic amines in boiling benzene gave mixtures of Z- and E-3-arylamino-2-(2-hydroxyaroyl)acrylonitriles and 2-amino-3-(aryl-iminomethyl)chromones. The latter can easily be obtained in the individual state when the reaction is carried out in the presence of triethylamine. In the case of primary aliphatic amines, the open-chain reaction product immediately undergoes cyclization into 3-alkyliminomethyl-2-aminochromones. The structures of the products were examined by 1D and 2D ¹H, ¹³C, and ¹⁵N NMR spectroscopy in DMSO-d₆ and CDCl₃.