Dimethylamino Naphthalene Research Articles

Base-promoted transformation of 2-C(O)R-1,8-bis(dimethylamino)naphthalenes into benzo[g]indole derivatives

1,8-Bis(dimethylamino)naphthalenes bearing 2-positioned trifluoroacetyl or ethoxycarbonyl group on treatment with 2-lithio-1,8-bis-dimethylamino)naphthalene undergo base-promoted transformation into benzo[g]indole derivatives in small to moderate yield, representing previously unknown mode of the pyrrole ring closure which proceeds via deprotonation of the NMe group.

Magnetic superbasic proton sponges are readily removed and permit direct product isolation.

Workup in organic synthesis can be very time-consuming, particularly when using reagents with both a solubility similar to that of the desired products and a tendency not to crystallize. In this respect, reactions involving organic bases would strongly benefit from a tremendously simplified separation process. Therefore, we synthesized a derivative of the superbasic proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) and covalently linked it to the strongest currently available nanomagnets based on carbon-coated cobalt metal nanoparticles. The immobilized magnetic superbase reagent was tested in Knoevenagel- and Claisen-Schmidt-type condensations and showed conversions of up to 99%. High yields of up to 97% isolated product could be obtained by simple recrystallization without using column chromatography. Recycling the catalyst was simple and fast with an insignificant decrease in catalytic activity.

Supra-molecular assembly of aromatic proton sponges to direct the crystallization of extra-large-pore zeotypes.

The combination of different experimental techniques, such as solid 13C and 1H magic-angle spinning NMR spectroscopy, fluorescence spectroscopy and powder X-ray diffraction, together with theoretical calculations allows the determination of the unique structure directing the role of the bulky aromatic proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) towards the extra-large-pore ITQ-51 zeolite through supra-molecular assemblies of those organic molecules.

1,8-Bis(bromomethyl)naphthalene in the synthesis of 1,5-diazacyclodecane and benz[de]isoquinoline proton sponges

A new 1,5-diazacyclodecane-based proton sponge 9 has been prepared by treatment of 1,8di(methylamino)naphthalene (7) with 1,8-bis(bromomethyl)naphthalene (8). Though the compound 9 is structurally related both to kinetically low-active 1,8bis(dimethylamino)naphthalene (1, parent proton sponge) and kinetically active 1,8bis(dimethylaminomethyl)naphthalene (2), X-ray and basicity studies have revealed that the proton sponge behavior of the former dominates. It is found that double alkylation of 1dimethylamino-8-methylaminonaphthalene (11) with 8 touches only the NHMe functionality and leads to the substitution of the N–Me group, yielding the previously unknown benz[de]isoquinoline proton sponge 15. The reaction of 8 with 1,8-diaminonaphthalene or 2,2dimethyl-2,3-dihydroperimidine gives, along with other products, proton sponge 18 with two benzisoquinoline fragments.

Designing bifunctional acid–base mesoporous hybrid catalysts for cascade reactions

Bifunctional mesoporous hybrid materials, containing both proton sponges and acid groups, have been prepared following different synthetic routes: co-condensation processes (sol–gel or micellar one-pot routes) or post-synthetic grafting of the organic functionalities. 1,8-Bis(dimethylamino)naphthalene (DMAN), a proton sponge with high pKa, was used as an organic functional builder base and 3-mercaptopropyltriethoxysilane (MPTES) as a pendant precursor of sulfonic acids. The bifunctional hybrid materials were extensively characterized and were investigated as heterogeneous catalysts for various one-pot C–C bond-forming cascade reactions such as deacetalization–Knoevenagel condensation or deacetalization–nitroaldol (Henry) reaction.

Tautomers of 4,5-dihydroxy-1,8-bis(dimethylamino)naphthalene and related boron compounds: A quantum-chemical study

The quantum-chemical method PBE0/cc-pV(D,T)Z was applied to determine structural parameters, relative energies, and dipole moments of the prototropic tautomers of 4,5-dihydroxy-1,8-bis(dimethylamino) naphthalene. According to the calculations, this compound can exist in the gas phase as low-polar molecules with one asymmetric intramolecular hydrogen bond. In a polarizable medium a pair of zwitter-ionic tautomers dominate of similar energy with two asymmetric intramolecular hydrogen bonds. These tautomers and a hypothetic heterocyclic analog containing a BH 2 + group instead of a proton between the nitrogen atoms are characterized by a high value of dipole moment and first hyperpolarizability. Mutual transformation of enantiomers (mirror antipodes) when transferring a proton from the hydroxy group to a neighboring atom in the O-boron-containing zwitter-ion is an example of strictly degenerate prototropic tautomerism.

Sublimation of New Matrix Candidates for High Spatial Resolution Imaging Mass Spectrometry of Lipids: Enhanced Information in Both Positive and Negative Polarities after 1,5-Diaminonapthalene Deposition

Matrix sublimation has demonstrated to be a powerful approach for high-resolution matrix-assisted laser desorption ionization (MALDI) imaging of lipids, providing very homogeneous solvent-free deposition. This work presents a comprehensive study aiming to evaluate current and novel matrix candidates for high spatial resolution MALDI imaging mass spectrometry of lipids from tissue section after deposition by sublimation. For this purpose, 12 matrices including 2,5-dihydroxybenzoic acid (DHB), sinapinic acid (SA), α-cyano-4-hydroxycinnamic acid (CHCA), 2,6-dihydroxyacetphenone (DHA), 2',4',6'-trihydroxyacetophenone (THAP), 3-hydroxypicolinic acid (3-HPA), 1,8-bis(dimethylamino)naphthalene (DMAN), 1,8,9-anthracentriol (DIT), 1,5-diaminonapthalene (DAN), p-nitroaniline (NIT), 9-aminoacridine (9-AA), and 2-mercaptobenzothiazole (MBT) were investigated for lipid detection efficiency in both positive and negative ionization modes, matrix interferences, and stability under vacuum. For the most relevant matrices, ion maps of the different lipid species were obtained from tissue sections at high spatial resolution and the detected peaks were characterized by matrix-assisted laser desorption ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) mass spectrometry. First proposed for imaging mass spectrometry (IMS) after sublimation, DAN has demonstrated to be of high efficiency providing rich lipid signatures in both positive and negative polarities with high vacuum stability and sub-20 μm resolution capacity. Ion images from adult mouse brain were generated with a 10 μm scanning resolution. Furthermore, ion images from adult mouse brain and whole-body fish tissue sections were also acquired in both polarity modes from the same tissue section at 100 μm spatial resolution. Sublimation of DAN represents an interesting approach to improve information with respect to currently employed matrices providing a deeper analysis of the lipidome by IMS.

Proton sponge-functionalized silica as high performance adsorbents for solid-phase extraction of trace perfluoroalkyl sulfonates in the environmental water samples and their direct analysis by MALDI-TOF-MS

1,8-Bis(dimethylamino)naphthalene (DMAN), a classical 'proton sponge', was functionalized on silica particles as a novel solid-phase extraction (SPE) adsorbent (DMAN@silica) for extracting perfluoroalkyl sulfonates (PFSs). High reproducibility and excellent extraction capability for PFSs were obtained in a wide pH range (3.0~8.5). The adsorbed PFSs on DMAN@silica sorbents could be efficiently eluted by 1,8-bis(tetramethylguanidino)naphthalene (TMGN) solution which is a proton sponge with higher proton affinity than DMAN. The elution could be directly analyzed by MALDI-TOF-MS using TMGN as matrix. Clear mass spectra for the PFSs were obtained due to no matrix ions interference observed. Furthermore, a novel strategy based on the DMAN@silica-SPE enrichment, followed by MALDI-TOF-MS analysis, was proposed and applied for PFSs quantification in environmental water samples. The calibration curves of each of the target analytes showed a wide linear dynamic range of response (0.1-10 ng L(-1) for perfluorooctane sulfonate (PFOS), perfluorohexyl sulfonate (PFHxS) and perfluorobutylsulfonate (PFBS)), which were over 2 orders of magnitude. The detection limits for PFOS, PFHxS, and PFBS were 0.021, 0.016, and 0.013 ng L(-1), respectively (S/N = 3). Recoveries of PFOS, PFHxS, and PFBS are in the ranges of 92-104%, 95-102%, and 98-109% for spiked river water samples. These results indicated that the prepared DMAN@silica adsorbents could efficiently enrich PFSs and that the proposed method is reliable.

Improved detection of phosphopeptides by negative ion matrix-assisted laser desorption/ionization mass spectrometry using a proton sponge co-matrix

Analysis of phosphopeptides is an important task in proteomic studies. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a technique very commonly used for such a purpose. Analysis of phosphopeptides by MALDI-MS is, however, still a challenging task due to the low ionization efficiency of phosphopeptides. In this study, we reported that by using a proton sponge 1,8-bis(dimethyl-amino)naphthalene (DMAN) as a co-matrix, detection of phosphopeptides by negative ion MALDI-MS could be greatly improved. Combination of DMAN with another matrix 6-aza-2-thiothymine (ATT) and additive diammonium hydrogen citrate (DHC) allowed much lower limit of detection, significantly reduced signal suppression effects and improved position-to-position reproducibility for detection of phosphopeptides by negative ion MALDI-MS. Potential applications of the matrix system in qualification of phosphopeptides and analysis of proteolytic digests of phosphorylated proteins were also demonstrated in this study.

Oxidation of 1-amino-4,5-bis(dimethylamino)naphthalene as a route to the double “proton sponges” based on dibenzo[a,h]phenazine and 1,1′-azonaphthalene

Behavior of 4-amino-1-dimethylamino- and 1-amino-4,5-bis(dimethylamino)naphthalenes sharply differs on their treatment with tosyl chloride and oxidation with the ButOK/O2 system. While the former upon the action of tosyl chloride in protic media is transformed to sulfonamide, the latter unexpectedly forms 4,5,11,12-tetrakis(dimethylamino)dibenzo[a,h]phenazine in ∼20% yield as a product of the competitive reaction, which represents the earlier unknown type of double “proton sponges”. In contrast to this, the oxidative dimerization of the indicated amines with ButOK/O2 leads to 5,12-bis(dimethylamino)dibenzo[a,h]phenazine and 4,5,4′,5′-tetrakis(dimethylamino)-1,1′-azonaphthalene, respectively. Possible mechanisms of these reactions were considered, as well as problems of coloring, solvatochromism, and protonation of the compounds obtained.

Quantitative detection of trace perfluorinated compounds in environmental water samples by Matrix-assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry with 1,8-bis(tetramethylguanidino)-naphthalene as matrix

Determination of perfluorinated compounds (PFCs) is very important because of their potential hazards to the environment and human health. In present work, 1,8-bis (tetramethylguanidino)-naphthalene (TMGN), a superbasic proton sponge, was firstly employed as the matrix for quantitative detection of acidic PFCs in environmental water samples by Matrix-assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF-MS). Several acidic PFCs, such as perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), were selected as model analytes for demonstrating the feasibility of the detection method. The results showed that deprotonated ions of these PFCs were detected without any other matrix ions interference. The achieved sensitivity with TMGN for PFOS detection was ten-fold higher than that with 1,8-bis (dimethyl-amino)-naphthalene (DMAN) which was used for the detection of fatty acid by MALDI-TOF-MS. The high sensitivity of this method made it feasible to monitor and quantify acidic PFCs in complicated environmental water samples. Furthermore, a novel combined strategy of solid phase extraction (SPE) followed by MALDI-TOF-MS detection was developed for quantifying PFCs in environmental water samples. The calibration curves with a wide linear dynamic range (0.1–10ngL−1 for PFOS, PFHxS, and PFBS, and 0.5–50ngL−1 for PFOA, PFNA, and PFDA.) were obtained. The limit of detection (LOD) for PFOS of this method was 0.015ngL−1 (a signal-to-noise ratio of 3), which was lower than the LOD (0.036ngL−1) obtained by high-pressure liquid chromatography/tandem mass spectrometry (LC–MS/MS) method. Moreover, the strategy was used to detect the selected PFCs in water samples collected from Xiaoqinghe river and Gaobeidian wastewater. The achieved concentrations of PFCs were closed to those obtained by LC–MS/MS method. It is indicated that the proposed MALDI-TOF-MS method with TMGN as the matrix is much reliable and can be used as an alternative method to detect trace PFCs in environmental water samples.

ChemInform Abstract: Unexpected Formation of Diels-Alder Spiro Adducts from 4-Hydroxymethyl Derivatives of ′Proton Sponge′.

Treatment of 4-hydroxymethyl derivatives of 1,8-bis(dimethylamino)naphthalenes 1a and 1b with concentrated hydrochloric acid leads to the formation of spiro compounds 7a and b in high yield.

ChemInform Abstract: Cyclometallated Compounds. Part 8. Double Cyclopalladation of Diacetylbenzene Dioximes and 1,5-Bis(dimethylamino)naphthalene.

ChemInform Abstract: Cyclometallated Compounds. Part 8. Double Cyclopalladation of Diacetylbenzene Dioximes and 1,5-Bis(dimethylamino)naphthalene.

ChemInform Abstract: Palladium-Catalyzed Asymmetric Arylation of 2,3-Dihydrofuran: 1,8-Bis( dimethylamino)naphthalene as an Efficient Base.

Abstract Reaction of 2,3-dihydrofuran with aryl triflate (1) in the presence of a base and a palladium catalyst, generated in situ from Pd(OAc)2 and (R)-BINAP, gave (R)-2-aryl-2,3-dihydrofuran (2) and a small amount of (S)-2-aryl-2,5-dihydrofuran (3). The enantiomeric purity of major product 2 was strongly affected by the base. 1,8-Bis(dimethylamino)naphthalene (proton sponge) as a highly basic and sterically demanding amine gave (R)-2 in high enantioselectivities ( > 96-87% ee) for a variety of aryl triflates.

Spectroscopic studies of intermolecular hydrogen bonding and proton transfer complexes of chromotropic acid with some amines in methanol

The proton transfer reactions between chromotropic acid (CTA) and some amines including benzylamine (BA), triethylamine (TEA), pyrrolidine (PY) and 1,8-bis(dimethylamino) naphthalene (DMAN) have been investigated spectrophotometrically in methanol. A long wavelength band at 365nm has been recorded due to the proton transfer (PT) complex formation. The proton transfer equilibrium constants KPT were estimated utilizing the minimum–maximum absorbances method. It has been found that KPT were not depend on the amine pKa values, but strongly depend on the formed structures of the PT complexes. Job’s method of continuous variations and photometric titrations were applied to identify the compositions of the formed PT complexes where 1:1 complexes (proton donor: proton acceptor) were produced. Due to the rapidity and simplicity of the proton transfer reactions and the stability of the formed complexes, a rapid and accurate spectrophotometric method for the determination of CTA was proposed for the first time.

ChemInform Abstract: Synthesis and Characterization of New 19-Vertex Macropolyhedral Boron Hydrides.

The new boron hydride anions 10-R-B19H19- (R = H, Thx) were synthesized by the reaction of M2[B18H20] (M = Na, K) with HBRCl.SMe2 (R = H, Thx) or HBCl2.SMe2 in diethyl ether. The anions are comprised of edge-sharing, nido 10- and 11-vertex cluster fragments, and are characterized by their 11B, 11B[1H], and 11B-11B COSY NMR spectra. The salt [(Ph3P)2N][B19H20].0.5THF crystallized in the triclinic space group P1 (a = 12.6344-(2) A, b = 13.5978(2) A, c = 14.1401(2) A; alpha = 77.402(2) degrees, beta = 81.351(2) degrees, gamma = 73.253(2) degrees). Possible synthetic pathways are discussed. The dianion B19H19(2-) is formed by deprotonation of B19H20- with Proton Sponge (1,8-bis(dimethylamino)naphthalene) in THF, and is identified on the basis of its 11B, 11B[1H], and 11B-11B COSY NMR spectra.

Salts of Mosher’s thioacid: agents for determining the enantiomer excess of SN2 substrates

Abstract The racemic and the (S)-enantiomer of Mosher’s thioacid, 2-methoxy-2-trifluoromethylphenylacetic thioacid, form air-stable salts with Proton Sponge [1,8-bis(dimethylamino)naphthalene]. These salts are powerful nucleophiles that react cleanly (SN2 inversion) in CDCl3 with optically active alkyl halides ranging in reactivities from unactivated alkyl bromides and iodides to benzylic bromides. The diastereomeric excess (de) of the thioester products indicates the enantiomeric excess (ee) of the starting alkyl halides.

Methodology To Probe Subunit Interactions in Ribonucleotide Reductases

Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides, providing the monomeric precursors required for DNA replication and repair. Escherichia coli RNR is a 1:1 complex of two homodimeric subunits, alpha2 and beta2. The interactions between alpha2 and beta2 are thought to be largely associated with the C-terminal 20 amino acids (residues 356-375) of beta2. To study subunit interactions, a single reactive cysteine has been introduced into each of 15 positions along the C-terminal tail of beta2. Each cysteine has been modified with the photo-cross-linker benzophenone (BP) and the environmentally sensitive fluorophore dimethylaminonaphthalene (DAN). Each construct has been purified to homogeneity and characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electrospray ionization mass spectrometry (ESI-MS). Each BP-beta2 has been incubated with 1 equiv of alpha2 and photolyzed, and the results have been analyzed quantitatively by SDS-PAGE. Each DAN-beta2 was incubated with a 50-fold excess of alpha2, and the emission maximum and intensity were measured. A comparison of the results from the two sets of probes reveals that sites with the most extensive cross-linking are also associated with the greatest changes in fluorescence. Titration of four different DAN-beta2 variants (351, 356, 365, and 367) with alpha2 gave a K(d) approximately 0.4 microM for subunit interaction. Disruption of the interaction of the alpha2-DAN-beta2 complex is accompanied by a decrease in fluorescence intensity and can serve as a high-throughput screen for inhibitors of subunit interactions.

19F NMR Spectroscopic Investigation of the Reaction of Bis(pentafluorophenyl)borinic Acid with a “Proton Sponge”: Deprotonation, Trimerization and Stepwise Dearylation

AbstractThe reaction of Ar2BOH (1, Ar = C6F5) with the proton sponge bis(dimethylamino)naphthalene (DMAN) in CD2Cl2 solution caused a series of strictly interlaced processes that have been investigated by variable‐temperature 1H and 19F NMR spectroscopy. The very slow equilibrium between the monomeric and cyclic trimeric forms of Ar2BOH was strongly accelerated by the presence of a catalytic amount of DMAN. Upon addition of stoichiometric DMAN (0.33 equiv.), all Ar2BOH was converted into a mixture of two boroxinate anions, namely [Ar6B3O3H2]– (2) and [Ar5B3O3H]– (3), in which the ratio of the two anions varied according to the reaction conditions. The formation of the dearylated anion 3 (accompanied by equimolar pentafluorobenzene) has been attributed to a reaction process parallel to that leading to the hexaaryl anion 2, involving base‐catalyzed hydrolysis of monomeric perfluoroborinic acid to its boronic analogue, followed by aggregation and condensation. Water plays a catalytic role in this process. In the presence of a small excess of DMAN, complete and instantaneous dearylation of 2 to 3 was observed. At temperatures lower than 233 K, the pentaaryl anion 3 was in equilibrium with its conjugate base. Slow further dearylation occurred at temperatures higher than 263 K, cleanly affording the tetraaryl anion [Ar4B3O3]– (5). Anions 3 and 5 have also been obtained in high yields from the condensation reaction between Ar2BOH and ArB(OH)2 (in the ratio 2:1 and 1:2, respectively), in the presence of stoichiometric DMAN. Mechanisms responsible for the stepwise dearylation from 2 to 3 and then from 3 to 5 have been discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Carbon-13 NMR Relaxation Study of 1,8-Bis(dimethylamino)naphthalene in Isotropic Solution

Carbon-13 nuclear spin relaxation in 1,8-bis(dimethylamino)naphthalene (DMAN) was investigated in a dimethylformamide- d 7 solution. In addition, the chemical shielding tensors were measured in the crystalline powder. Detailed analysis of (13)C longitudinal relaxation in this molecule yielded its rotational diffusion tensor. Comparison to the protonated form of DMAN, DMANH(+), leads to conclusions concerning interaction of the latter with its counterion.