N-alkyl Groups Research Articles

Hydroacridines XIX [1]. 13C NMR Spectra of Several N-Alkyl-tetradecahydroacridines and their Protonated Species: Investigation of the N-Epimeric Equilibria of the N-Alkyl Groups in the Amines and in the Salts

(4aα,8aβ,9aβ,10aα)-Tetradecahydro-10-methylacridin, (4aα,8aβ,9aβ,10aα)-10-ethyl-tetradecahydroacridin, (4aα,8aα,9aβ,10aα)-tetradecahydro-10-methylacridine, (4aα,8aα,9aβ,10aα)-10-ethyl-tetradecahydroacridin and their products of protonation with trifluoroacetic acid were studied by 13C NMR spectroscopy. The first two amines give rise to a pair of N-diastereomeric salts, whereas the latter two yield only the salts with equatorial N-alkyl groups. The N-epimeric equilibria of the N-alkyl groups (equatorial-axial) in the salts and in the amines are discussed.

Comparison of Interfacial Width of Block Copolymers of d8-Poly(methyl methacrylate) with Various Poly(n-alkyl methacrylate)s and the Respective Homopolymer Pairs as Measured by Neutron Reflection

The compatibility of d8-poly(methyl methacrylate) (d8-PMMA) and a series of poly(n-alkyl methacrylate)s (PnAlkMA) is studied by systematic variation of the length of the n-alkyl group from ethyl (E...

Synthesis and Pore Size Control of Cubic Mesoporous Silica SBA-1

The formation of silica−surfactant mesostructures has been studied under various acidic conditions using tetraethyl orthosilicate and hexadecyltriethylammonium bromide. The synthesis conditions have been optimized in order to obtain the cubic (Pm3n) mesoporous molecular sieve designated as SBA-1 of high quality. The pore diameter of the SBA-1 material has been controlled within the range of 1.4−2.7 nm by expanding the surfactant micelles with 1,3,5-trimethylbenzene or substituting the hexadecyl group of the surfactant with other n-alkyl groups (C12H25 to C18H37).

Optical Second Harmonic Generation in Achiral Bis(n-alkylamino)dicyanoquinodimethanes: Alkyl Chain Length as the Design Element

Chain length of substituted n-alkyl groups is proposed to be a convenient design element for the generation of noncentrosymmetric crystal lattices of interest in optical second harmonic generation (SHG). Powder studies on 7,7-Bis(n-alkylamino)-8,8-dicyanoquinodimethanes indicate that moderate solid-state optical SHG is obtained when the alkyl chains are of length 4, 5, and 6, and no detectable SHG occurs when the chains are of length 0, 3, 7, 8, and 12. The significant role of the intermediate alkyl chain length in generating noncentric crystal lattices is examined using the crystal structures of the propyl, butyl, and octyl derivatives presented in this paper.

Polymer-Supported N-Alkyl-α ,α-diphenyl-L- prolinols as Catalysts forthe Alkylation of Aldehydes Using Diethylzinc.

Polystyrene beads containing N-alkyl-α,α-diphenyl-L-prolinol moieties (7) linked to the support via a long N-alkyl group, which also serves as a spacer chain, have been prepared. When used to catalyse the reactions of aldehydes with diethylzinc at 10 mole % in toluene at 20°C they afford the expected alcohols in 59–83% e.e. Where comparisons can be made with the results obtained with N-methyl-α,α-diphenyl-L-prolinol (3), the PS(polymer- supported) catalysts afford lower percentage e.e. values. Evidence is provided that this is due in part to the presence of the spacer chain, and in part because with the PScatalysts not all the catalyst sites are readily accessible. The latter means that the PScatalysts cannot compete satisfactorily with the uncatalysed reactions between aldehydes and diethylzinc which produce racemates. Thus, if higher percentage e.e. values are to be obtained in future with PS α,α-diphenyl-L-prolinol derivatives, the catalyst sites will most likely need to be bound to the polymer via the phenyl groups or substituents on the five-membered ring.

Involvement of CYP2D6 in the in vitro metabolism of amphetamine, two N-alkylamphetamines and their 4-methoxylated derivatives

1. Amphetamine (AM) and five amphetamine derivatives, N-ethylamphetamine (NEA), N-butylamphetamine (NBA), 4-methoxyamphetamine (M-AM), 4-methoxy-Nethylamphetamine (M-NEA) and 4-methoxy-N-butylamphetamine (M-NBA) were incubated with microsomal preparations from cells expressing human CYP2D6 to determine whether the enzyme was capable of catalyzing the direct ring oxidation of all substrates; the N-dealkylation of NEA, NBA, M-NEA and M-NBA; and the O-demethylation of M-AM, M-NEA and M-NBA. 2. None of the six compounds examined was N-dealkylated to any extent. 3. The only metabolites produced from AM, NEA and NBA were the corresponding ring 4-hydroxylated compounds, and the rates of formation were low. 4. All ring 4-methoxylated substrates were efficiently O-demethylated by CYP2D6 to their corresponding phenols. The size of the N-alkyl group influenced the rates of formation of these phenolamines. In contrast to reported findings with 2- and 3-methoxyamphetamines, none of the 4-methoxyamphetamines was ring-oxidized in the CYP2D6 enzyme system to 2- or 3-hydroxy-4-methoxyamphetamines or to dihydroxyamphetamines.

The influence of N-alkyl groups on the properties of squarylium cyanine dyes

Dyes with strong intermolecular interactions often exhibit low solubility, which restricts their application in some areas. Solubility can be improved by introducing substituent groups with a steric hindrance capacity. By enlarging the intermolecular distance, the interaction can be reduced, and so the solubility is higher. In this report, bis(2,3,3-trimethylindolenium-2-ylidene) squaraines with different branch chain alkyl groups on the nitrogen atom were synthesized and the relationship between substituents and solubility in different solvents, melting point and photophysical properties in solution are discussed.

Polydiacetylenes with Long Wavelength Absorption

A series of 1,6-disubstituted-2,4-hexadiynes, where the substituents are para-substituted benzene rings that have either a dicyanovinyl or tricyanovinyl group as one substituent and have either an oxygen or N-alkyl group connecting to the hexadiyne chain, was designed to lead to polydiacetylenes (PDAs) with long wavelength absorption, and these PDAs were synthesized. These new compounds, in contrast to other diacetylene monomers, are relatively insensitive to ultraviolet light and ionizing radiation under ambient temperature and require heating above 100 °C to bring about preparatively useful conversion to polymer. The new PDAs have the usual en-yne backbone structure as shown by Raman spectroscopy. Three of the new PDAs exhibit maxima in diffuse reflectance at wavelengths as long as or longer than the PDA of 1,6-di-N-carbazolyl-2,4-hexadiyne.

Correlation between chromatographic and physicochemical properties of stationary phases in HPLC: C 30 bonded reversed-phase silica

In comparison to conventional C 18 phases, C 30 phases exhibit superior shape selectivity for the separation of isomers of carotenoids and vitamins. To obtain this enhanced recognition capability the HPLC separation must be performed at a well-defined temperature. At higher temperatures the capability of differentiating between different stereochemical isomers is lost, resulting in peak coelution. This separation behaviour is primarily dependent upon the organisation of the C 30 alkyl chains on the silica surface which can be visualised as two domains, the more ordered domain containing relatively rigid n-alkyl groups with trans conformations and the less ordered environment containing more flexible n-alkyl groups with gauche conformations. The ratio between trans vs. gauche conformations of the n-alkyl groups directs the shape selectivity of the C 30 phase. The temperature-dependent interconversion of trans to gauche conformations can be monitored by temperature-dependent solid-state nuclear magnetic resonance (NMR) and suspended-state NMR measurements and visualised by molecular modelling calculations. Thus a direct correlation between chromatographic and physicochemical properties of C 30 bonded phases is possible.

Effects of the Hydrophobicity of the Reactants on Diels−Alder Reactions in Water

To assess the importance of the hydrophobicity of different parts of diene and dienophile on the aqueous acceleration of Diels-Alder reactions, second-order rate constants have been determined for the reactions of cyclopentadiene (1), 2,3-dimethyl-1,3-butadiene (4), and 1,3-cyclohexadiene (6) with N-methyl-, N-ethyl-, N-propyl-, and N-butylmaleimide (2a-d) in different solvents. All these reactions are accelerated in water relative to organic solvents as a result of enhanced hydrogen bonding and enforced hydrophobic interactions during the activation process. The beneficial influence of water as compared to 1-propanol on the rate of the Diels-Alder reaction of 4 with 2a-d increases linearly with the length of the alkyl chain of 2. In contrast, for the reaction of both 1 and 6 with 2a-d, no such effect was observed. This difference can be explained by a hydrophobic interaction between the methyl groups of 4 and the N-alkyl group of 2 during the activation process. In the reactions of 1 and 6, lacking the methyl substituents, this interaction is not possible and elongation of the alkyl chain from ethyl onward does not result in an additional acceleration by water. The enhanced hydrophobicity near the reaction center of dienes 4 and 6 compared to 1 results in an increased aqueous acceleration of the Diels-Alder reactions of the former dienes with 2a. These data indicate that an increase in the hydrophobicity close to the reaction center in the diene has a much more pronounced effect on the rate acceleration in water than a comparable increase in hydrophobicity in the dienophile further away from the reaction center. The Gibbs energies of transfer of initial state and activated complex of the Diels-Alder reactions under study have been determined. As expected, for all reactions the initial state in water is destabilized compared to that in 1-propanol. This destabilization becomes more pronounced when the nonpolar character of diene (close to the reaction center) or dienophile (distant from the reaction center) is increased. Likewise, an increase in the nonpolar character of 2 results in a destabilization of the activated complex. In contrast, addition of methyl or methylene units to the diene is not accompanied by a significant destabilization of the activated complex in water as compared to 1-propanol. We conclude that hydrophobic groups near the reaction center seem to lose their hydrophobic character completely in the activated complex of the Diels-Alder reaction, whereas more distant groups retain their nonpolar character throughout the reaction.

Solvatochromism and Structure of Acetylacetonatocopper(II) Complexes with N,N′-Dipropyl-, N,N,N′,N′-Tetrapropyl-, and N,N- and N,N′-Diisopropylethylenediamines

Abstract Seven copper(II) complexes of the general formula [Cu(acac)(diam)]X were prepared, where acac and diam stand for acetylacetonate and one of the diamines in the title, and X− for a bulky univalent anion, respectively. Their solvatochromism was compared with that of the corresponding complexes with N,N,N′,N′-tetramethylethylenediamine and related diamines, to see the effect of their bulky N-alkyl groups. X-ray crystal analyses showed that the perchlorates of N,N′- and N,N-diisopropyl complexes are apparently 6- and 5-coordinated, respectively, in their crystals, although their ClO4− ions are held extremely weakly and are easily driven out by solvent molecules in solution, leading to their solvatochromism. The Cu–N and Cu–O(acac) bond distances in the former, 199.5(4)/202.4(5) and 190.6(4)/190.1(4) pm, respectively, are similar to each other, while the Cu–N(isopropyl)2 distance, 206.4(9) pm, in the latter is notably longer than the Cu–NH2 distance, 196(1) pm.

Synthesis and characterization of nickel(II) complexes of di- N-alkylated 14-membered tetraaza macrocycles containing cyclohexane rings via regioselective alkylation reaction

Square-planar nickel(II) complexes of new di- N-alkylated 14-membered tetraaza macrocycles 6,17-dimethyl (L 5),6,17-diethyl (L 6), and 6,17-bis(n-propyl) (L 7) derivatives of 3,14-dimethy1-2,6,13,17-tetraazatricyclo-[16,4,0 1.18O, 7.12]docosane (L 1) have been prepared by one-step, regioselective reaction of [NiL 1] 2+ with RI (R  Me, Et, or n-Pc) in basic Me 2SO solution. The nickel(II) complexes were characterized by 1H and 13C NMR spectroscopy and/or by single crystal X-ray crystallography. Crystal structures of [NiL 1] (ClO 4) 2 and the di- N-propyl derivative [NiL 7] (ClO 4) 2 show that the two complexes have normal square-planar coordination geometries with the nickel atoms lying on the N 4 planes; however, the NiN bond distances of the latter are about 0.03 Å longer than those of the former. The electronic spectra, redox potentials and/or structures of the nickel(II) complexes are strongly affected by the presence of N- and C-substituents, but little affected by the nature of the N-alkyl groups.

Catalytic Preparation of Aziridines with an Iron Lewis Acid.

The iron Lewis acid, [(eta(5)-C(5)H(5))Fe(CO)(2)(THF)](+)[BF(4)](-), was found to be an effective catalyst for the preparation of aziridines. This new method provides a facile, one-step route to predominantly cis-aziridines, with yields up to 95%, from compounds with a diazo functionality and a variety of substituted N-benzylidene imines with N-aryl or N-alkyl groups. The reaction mechanism is believed to proceed through an electrophilic iminium ion intermediate. To support this idea, the iron Lewis acid-imine complex [(eta(5)-C(5)H(5))Fe(CO)(2)(PhCH=NPh)](+)[BF(4)](-) was prepared, characterized, and reacted with different diazo compounds to provide the resultant cis-aziridines. Alternatively, it may be possible that the aziridines were derived from an electrophilic carbenoid intermediate, as is often proposed. Thus, the iron carbene [(eta(5)-C(5)H(5))Fe(CO)(2)(CHPh)](+)[SO(3)CF(3)](-) was prepared and treated with N-benzylideneaniline; however, the resultant aziridine was not formed.

Report on the preparation of deuterium-labelled aconitine and mesaconitine and their application to the analysis of these alkaloids from body fluids as internal standard

Improved analysis of aconitine and mesaconitine, highly toxic compounds from Aconitum species, in body fluids by gas chromatography–selected ion monitoring with their deuterium-labelled analogues as internal standards (I.S.s) is described. Deuterium-labelled analogues of aconitine and mesaconitine were synthesized by the substitution of the N-alkyl group for a deuterium-labelled one. The mass spectra of the derivatives of the deuterium labels closely resembled that of the nonlabelled compounds except for an obvious mass shift produced by substitution of the deuterium atoms at N-alkyl groups. Using these deuterium-labelled compounds as I.S.s, the standard curves for aconitine and mesaconitine were linear ( r 2=0.999 each) in the concentration range of 50 pg to 50 ng, respectively. The detection limit of the alkaloids was 10 pg each per injection. The recovery, accuracy and precision of the analysis were evaluated with three different concentration of spiked human blood and urine ( n=5 each). The recovery rates ranged from 97.6% to 101.3% and the standard deviations of the interseries ranged from 2.1% to 3.9%. These I.S.s give us a more precise analysis and may be useful in examining the behavior of these alkaloids in the human body.

Reactivity of perfluoro- n-alkyl radicals with reluctant substrates. Rates of addition to R FCH 2CH=CH 2 and R FCH=CH 2

Conditions for conducting competitive experiments involving slow reactions of perfluoroalkyl radicals have been defined. A revised value for the rate constant for hydrogen abstraction from Et 3SiH is reported [(5.0±0.4) × 10 5 M −1s −1], as are the rate constants for addition of the n-C 4F 9 • radical to CH 2CHCH 2C 4F 9 [1.15 ± 0.11) × 10 6 M −1s −1] and to CH 2CHC 4F 9 [2.6 ± 0.2) × 10 5 M −1s −1] at 25 °C.

Electroluminescent properties of naphthalimide derivative thin film devices

N-alkyl or arenyl-4-acetylamide-1,8-naphthalimides (NA) were synthesized by reaction of 4-acetylamide-1,8-naphthalic acid with organic amines. Optical properties were studied in the UV-visible region. By using Joule evaporation thin films of the NA, the double layer of EL devices (ITO/PVK/NA/Al) were fabricated. Yellow and green EL emission at around 569.0–504.2 nm was observed. It was found that the emission wavelength of the devices using naphthalimides with bulkier N-alkyl groups shifted to red while the emission wavelength of those devices using naphthalimides with N-arenyl substituted groups shifted to blue. This is identified with the results calculated by the MINDO/3 model. Moreover, experimental results revealed that the Joule heat by non-radiative decay has a significant affect on the device life, and the life of the device using naphthalimide compounds with high melting points is longer than that of the device fabricated using those with low melting points.

Steric and Electronic Influences on the Diastereoselectivity of the Rh2(OAc)4-Catalyzed C−H Insertion in Chiral Ester Diazoanilides: Synthesis of Chiral, Nonracemic 4-Substituted 2-Pyrrolidinones

A series of N-substituted N-(4-methoxyphenyl)-α-(alkoxycarbonyl)-α-diazoacetanilides, 10 and ent-10, wherein the alkoxy unit is a chiral auxiliary group [(−)-7 or (+)-8)], was prepared. The Rh2(OAc)4-catalyzed intramolecular C−H insertion reaction of 10 and ent-10, under optimized reaction conditions, was investigated as a route for the preparation of chiral, nonracemic 4-substituted 2-pyrrolidinones. The cyclization reaction led only to 2-pyrrolidinone and 2-azetidinone products; the former products were obtained as major and, in a few cases, as exclusive products. The type and nature of the N-substituent in 10 or ent-10 was found to govern the diastereoselectivity of the reaction. With N-alkyl groups, steric effects play an important role in determining the diastereoselectivity of the reaction. However, with N-arylethyl substituents, electronic effects transmitted by the aryl substituents influenced the diastereoselectivity of the C−H insertion reaction. Specifically, electron-donating substituents were found to markedly attenuate the diastereoselectivity of the reaction. The diastereoselectivity of the reaction ranged from moderate to high (37−98%). A transition-state model to explain the observed diastereoselectivity is provided. The synthetic utility of the method is demonstrated by the stereoselective synthesis of the medicinally important, unnatural amino acid trans-4-cyclohexyl-l-proline 23.

Photoreactivities of Donor-Acceptor Crystals between 3,5-Dinitrobenzoic Acid and N-Alkylcarbazoles

A variety of 1: 1 charge-transfer (CT) crystals were prepared by using mainly dinitrobenzoic acids (as the acceptor) and carbazoles (as the donor). Most of the CT crystals prepared from 3,5-dinitrobenzoic acid (3) and a series of N-alkylcarbazoles (1a−1h) underwent photoredox reactions initiated by the excited nitro group, leading to α-oxidation of N-alkyl groups (13−15). The reactions were much more efficient in the solid state than in solution. These solid-state photoreactivities could be, on the whole, correlated with the C···O distances between the carbazole N-α-carbon atom and the nitro oxygen atoms nearby.

Heteroaryl radicals in synthesis: Radical cyclisation reactions of 2-bromoindoles

The synthesis and radical cyclisations of 2-bromoindoles carrying an unsaturated N-alkyl group is described.

Diastereoselective α-alkoxylation of lactamide N-alkyl groups via intramolecular formation of oxonium ions as the key intermediate

Stereoselective introduction of an alkoxy group to the amine unit of lactamide derivatives, under electrochemical oxidation conditions, was investigated based upon the assumption that a cyclic oxonium ion can be formed between the alkoxy substituent on the chiral center and a carbocation generated at the α-position of N-alkyl substituents. With N-monosubstituted lactamides, diastereoselectivity in the N-α-alkoxylated product was not observed. With N,N-disubstituted lactamides, however, the selectivity appeared though in low ratios (≈2.2). Requisite factors that govern the stereoselectivity, i.e. nucleophilicity of both internal and external nucleophiles and substitution on amine units, were also examined.