Dry DMF Research Articles

A new synthesis of alkynyl tellurides promoted by CsOH and 4 Å MS

The mixture of cesium hydroxide and terminal alkynes in dry DMF in the presence of 4 Å molecular sieves was stirred for 3.0 h at room temperature under N 2, then aryltellurenyl bromide in THF was added, and the reaction mixture was stirred for 2.0 h. Alkynyl tellurides were obtained in about 90% yields by flash chromatography.

New synthesis of methyl 5-aryl or heteroaryl pyrrole-2-carboxylates by a tandem Sonogashira coupling/5- endo- dig-cyclization from β-iododehydroamino acid methyl esters and terminal alkynes

A new and versatile ‘Pd’/CuI catalyzed protocol was developed for the synthesis in good to high yields of substituted pyrroles from N-Boc-β-iododehydroamino acid methyl esters and several terminal alkynes. This one-pot, two-step procedure occurs by a Sonogashira coupling followed by a 5- endo- dig-cyclization, which involves the nitrogen atom of the dehydroamino acid. After several experiments using different Pd(0) and Pd(II) species it was possible to establish the more general reaction conditions, which are: the use of a Pd(II) catalyst, CuI and Cs 2CO 3 as base in dry DMF at 70 °C. The best yields were obtained with arylacetylenes bearing electron-donating groups and with electron-rich heteroarylacetylenes.

Anagostic Interactions and Catalytic Activities of Sterically Bulky Benzannulated N-Heterocyclic Carbene Complexes of Nickel(II)

Nickel(II) bis(benzimidazolin-2-ylidene) complexes of the general formula [NiBr2(NHC)2] (NHC = 1,3-dibenzylbenzimidazolin-2-ylidene, 7; NHC = 1,3-diisopropylbenzimidazolin-2-ylidene, 8; NHC = 1,3-dibenzhydrylbenzimidazolin-2-ylidene, 9; NHC = 1,3-diisobutylbenzimidazolin-2-ylidene, 10; NHC = 1-isopropyl-3-benzylbenzimidazolin-2-ylidene, 11; NHC = 1-benzhydryl-3-benzylbenzimidazolin-2-ylidene, 12) have been prepared and fully characterized by spectroscopic methods and single-crystal X-ray structure analyses. All complexes adopt a square-planar geometry with nickel as the crystallographic inversion center and a trans arrangement of the carbene ligands. For complexes 11 and 12, bearing unsymmetrically substituted ligands, only the trans-anti configuration was found in the solid state. In addition, the structures of 8, 9, 11, and 12 reveal a fixed orientation of the N-isopropyl and N-benzhydryl substituents with the C−H groups pointing to the nickel(II) center to maximize rare intramolecular C−H···Ni anagostic or preagostic interactions. The large downfield shift of these C−H protons in the 1H NMR spectrum compared to their precursor salts indicates that these interactions are retained in solution. Preliminary catalytic studies show that complexes 7−12 are active in the Ullmann coupling of bromobenzene and 4-bromoanisole. In particular, complexes 8, 9, and 12, with sterically more demanding ligands, exhibit the best catalytic activities. The coupling reaction was found to be successful when carried out in neat [Bu4N]Br as ionic liquid, but not in dry DMF or in DMF with [Bu4N]Br as an additive.

Synthesis and characterization of new metal-free and nickel(II) phthalocyanines containing hexaazadioxa macrobicyclic moieties

Novel symmetrically tetrasubstituted metal-free and metallophthalocyanines (5) and (6) which contain four hexaazadioxamacrobicycles on peripheral positions, have been synthesized. Macrobicyclic compound 3 and has been prepared by reaction of (1,3,6,9,11,14- hexaazatricyclo[12.2.1.16,9])octadecane (1) with 1,2-bis(2-iodoethoxy)-4,5-dibromobenzene (2). Compound 4 has been synthesized by reaction of compound 3 with CuCN in dry DMF. The target symmetrical phthalocyanines were separated by column chromatography and characterized by elemental analyses, 1H, 13C–NMR, IR, UV–Visible and FAB mass spectroscopies.

(μ-Hydroxo)-platinum complex-catalyzed enantioselective aldol reaction of aldehydes with 1-methoxy-2-methyl-1-(trimethylsilyloxy)propene in DMF

[(( R)-BINAP)Pt(μ-OH)] 2·2OTf catalyzed the enantioselective aldol reaction of aldehydes with 1-methoxy-2-methyl-(1-trimethylsilyloxy)propene at room temperature in dry DMF in high yields with enantioselectivity up to 92%. This is a versatile example of the catalytic enantioselective aldol reaction using a silyl ketene acetal promoted by (μ-hydroxo)-platinum complexes under mild conditions.

On the Synthesis and Reactivity of 4-(Oxiran-2-ylmethoxy)cinnoline: Targeting a Cinnoline Analogue of Propranolol

The title compound (2) was prepared by reaction of 4-chlorocinnoline with glycidol/sodium hydride in dry DMF, since treatment of cinnolin-4-ol with epichlorohydrin as well as oxidation of 4-allyloxycinnoline did not succeed. Reaction of 2 with primary and secondary amines leads to aminoalcohols characterized by a high tendency to rearrangement and/or elimination. The obtained products were subjected to detailed multinuclear (1H, 13C, 15N) NMR studies.

Synthesis, characterization and nonlinear absorption of novel octakis-POSS substituted metallophthalocyanines and strong optical limiting property of CuPc

In this study, the preparation of some novel metallophthalocyanine (MPcs) complexes substituted with octakis(mercaptopropylisobutyl-POSS) functional group was achieved. By the reaction of [1-(3-mercapto)propyl-3,5,7,9,11,13,15-isobutylpentacyclo[9.5.1.1(3,9).1(5,15).1(7,13)]octasiloxane 1 with 4,5-dichloro-1,2-dicyanobenzene 2 in THF as the solvent in the presence of K2CO3 as the base, the phthalonitrile derivative 3 was synthesized. Compound 3 reacted with CoCl2 x 6H2O in ethylene glycol to furnish a novel cobalt(II) phthalocyanine . The tetramerization of 3 with urea and CuCl in the absence of solvent gave the novel Cu(II) phthalocyanine 4; while with Zn(OAc)2 x 2H2O in dry DMF gave the novel zinc(ii) phthalocyanine 6. The structures of the target compounds were confirmed by elemental analysis, UV/VIS, IR, MALDI-TOF MS and 1H NMR spectra. Nonlinear absorptions of MPcs in chloroform solution were investigated by using Z-scan measurement technique with 4 ns pulses at 532 nm wavelength. While CuPc 5 showed very high nonlinear absorption, MPcs 4 and 6 did not show considerable nonlinear absorption. Investigations of optical limiting properties of 5 revealed that this material is a very good candidate for optical limiting applications.

Radiolabeling and in vitro and in vivo evaluation of [18F]-FE-DABP688 as a PET radioligand for the metabotropic glutamate receptor subtype 5

Fluoroethyl-desmethyl-ABP688 (FE-DABP688) is a novel derivative of the previously described positron emission tomography (PET) ligand 3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone-O-[11C]-methyl-oxime. FE-DABP688 was radiolabeled with fluorine-18 and characterized as a PET imaging agent for the metabotropic glutamate receptor subtype 5 (mGluR5). FE-DABP688 was radiolabeled by reacting 2-[18F]-fluoroethyl tosylate with the sodium salt of 3-(pyridin-2-ylethynyl)-cyclohex-2-enone-oxime in dry DMF. The in vitro affinity of [18F]-FE-DABP688 for mGluR5 was determined by Scatchard analysis of saturation binding data using rat whole-brain membranes (without cerebellum). Further in vitro characterization of the tracer involved plasma stability and lipophilicity testing. In vivo evaluation of [18F]-FE-DABP688 was performed by postmortem biodistribution experiments and PET studies in rats using the dedicated small-animal PET tomograph quad-HIDAC. The radiotracer was obtained in good radiochemical yields in an overall synthesis time of 150 min. The radiochemical yield after semipreparative HPLC was 25+/-8% (n>7, decay corrected), and specific activity was 30+/-5 GBq/micromol (n>7). [18F]-FE-DABP688 exhibited optimal lipophilicity with a logD value of 2.1+/-0.1 and high plasma stability. Saturation assays of [(18)F]-FE-DABP688 revealed a single high-affinity binding site with a dissociation constant (Kd) of 1.6+/-0.4 nM and a Bmax value of 119+/-24 fmol/mg protein. PET scanning indicated radioactivity uptake in mGluR5-rich regions such as the hippocampus, striatum and cortex, while radioactivity accumulation in the cerebellum, a region with negligible mGluR5 density, was significantly lower. Biodistribution studies showed a similar distribution pattern of [18F]-FE-DABP688 binding in the brain. The hippocampus-to-cerebellum and striatum-to-cerebellum ratios were 1.81+/-0.16 and 1.93+/-0.36, respectively. Blocking studies using coinjection of [18F]-FE-DABP688 and unlabeled 2-methyl-6-((3-methoxyphenyl)ethynyl)-pyridine (1 mg/kg) revealed more than 45% specific binding in the hippocampus and striatum, thus demonstrating the in vivo specificity of tracer binding. [18F]-FE-DABP688 may be a useful PET tracer for imaging mGluR5 in rodents.

Preparation of Novel Nonlinear Optical Polyester with Enhanced Thermal Stability of Dipole Alignment

zation of dipole alignment of the NLO chromophore, which was a part of the polymer backbone. In this work we prepared novel polyester containing 2,3-dioxybenzylidenemalononitrile groups as NLO-chromophores. We selected 2,3-dioxybenzylidenemalononitrile groups as NLO-chromophores because they have a large dipole moment and are rather easy to synthesize. Furthermore, 2,3-dioxybenzylidenemalononitrile group constitutes novel Y-type NLO polyester (Fig. 1c), and this Y-type NLO polyester has not been reported in the literature. These mid-type NLO polymers are expected to have the advantages of both main-chain and side-chain NLO polymers: stabilization of dipole alignment and good solubility. After confirming the structure of the resulting polymers we investigated the properties such as solubility, Tg, thermal stability, second harmonic generation (SHG) activity and relaxation of dipole alignment. We now report the results of the initial phase of the work. Results and Discussion 2,3-Di-(2'-vinyloxyethoxy)benzaldehyde (1) was prepared by the reaction of 2-chloroethyl vinyl ether with 2,3dihydroxybenaldehyde. 2,3-Di-(2'-vinyloxyethoxy)benzylidenemalononitrile (2) was prepared by the condensation reaction of 1 with malononitrile. Compound 2 was hydrolyzed to yield acetaldehyde and diol 3. Diol 3 was condensed with terephthaloyl chloride in a dry DMF solvent to yield polyester 4 containing the NLO-chromophore 2,3-dioxybenzylidenemalononitrile group The synthetic route for polyeater 4 is presented in Scheme 1. The polymerization yield was 88-92%. The chemical structures of the resulting polymers were confirmed by 1 H NMR, IR spectra, and elemental analysis. Elemental analysis results fit the polymer structures. 1 H NMR spectra of the polymers showed a signal broadening due to polymerization, but the chemical shifts are consistent with the proposed polymer structures. The IR spectra of the same polymer samples show a strong carbonyl peak near 1722 cm −1 indicating the presence of ester bond. The same polymer sample also shows a strong absorption peak near 2229 cm –1 and 1572 cm –1 due to the nitrile and olefin groups, respectively. These results are consistent with the proposed structures, indicating that the NLO-chromophore remained intact during the polymeri

An efficient substituent dependent synthesis of congested pyridines and pyrimidines

An efficient and versatile synthesis of various congested pyridines 3a– h, 6a, b, 8a– n, 10a– g, and 16a, b, and (pyrimidin-4-yl)acetonitriles 13a– g has been delineated by base catalyzed ring transformation of suitably functionalized 2 H-pyran-2-ones 1a– h, 5, 7, and 15 by formamidine acetate 2a, acetamidine hydrochloride 2b, S-methylisothiourea 9a, pyrazol-1-yl-carboxamidine 9b, and arylamidine hydrochloride 12 separately in the presence of powdered KOH in dry DMF.

Dimethylformamide dimethyl acetal in heterocyclic synthesis: Synthesis of polyfunctionally substituted pyridine derivatives as precursors to bicycles and polycycles

Abstractmagnified imagePolysubstituted pyridines 11a,c and 12 were prepared by the reaction of benzoylacetone with dimethylformamide dimethyl acetal followed by treatment with cyanothioacetamide 9a, cyanoacetamide 9b and the anion of malononitrile dimmer 9c in dry DMF. When the reaction was carried out in ethanol as a solvent and piperidine as a base afforded 14a,b. Thienopyridines 16a,b were prepared by the reaction of pyridinethiones 11a and 14a with 2‐chloro‐N‐p‐tolyl‐acetamide (15). Further reaction of thienopyridines 16a,b with either DMFDMA or nitrous acid to gave 17a,b and 18a,b respectively. The reaction of pyridine derivative 11c with hydrazine and phenylhydrazine afforded the tricyclic compounds 19a,b.

Synthesis and Functionalization of Germanium Triphenylcorrolate: The First Example of a Partially Brominated Corrole

AbstractGe complexes of 5,10,15‐triphenylcorrole were prepared in refluxing dry DMF using GeCl4 as the source of Ge. Chromatographic separation of the crude reaction mixture afforded the μ‐oxo dimer 1 and the methoxy derivative 2a. The corresponding chloride 2b can be obtained by treatment of 1 or 2a with HCl. The reaction of 2a with Br2 in CHCl3/py afforded the hexabromo derivative 3 as the main product, giving the first indication of the regioselective substitution of pyrroles B and C on the corrole ring. The fully brominated open‐chain tetrapyrrole 4 was also characterized as a reaction by‐product. Different partially brominated Ge complexes 5 and 6 have been obtained by variation of reaction conditions, while the heptabromo derivative was obtained in a mixture with the corresponding fully brominated Gecorrole. Photophysical characterization of Ge corrolates confirmed the high fluorescence quantum yield of such complexes, and also led to the first observation of phosphorescence emissions from corrole complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Partially Fluorinated Heterocycles from 4,4-Bis(trifluoromethyl)-hetero-1,3-dienes via C–F Bond Activation – Synthesis of 2-Fluoro-3-(trifluoromethyl)furans

An efficient synthesis of 2-fluoro-3-(trifluoromethyl)furans was developed. Keystep of the reaction sequence is a [4 + 1] cycloaddition reaction of tin(II)chloride to 4,4-bis(trifluoromethyl)-1-oxabuta-1,3-dienes. At elevated temperatures the tin heterocycles are transformed into 1-aryl-4,4-difluoro-3-(trifluoromethyl)but-3-en-1-ones which on treatment with sodium hydride in dry DMF give 2-fluoro-3-(trifluoromethyl)furans. The single fluorine bound to C-(2) can be readily replaced by various N-, O-, S-, and C-nucleophiles and dinucleophiles.

On the Electrochemistry of 2,4,6-triphenylnitrobenzene

Cyclic voltammetry at a glassy carbon electrode of 2,4,6- triphenylnitrobenzene (1) in DMF shows two reversible one- electron reductions. Preparative reduction of 1 yields 2,4,6- triphenylaniline under both acidic and alkaline conditions and in DMF in the presence of acetic anhydride. On reduction in dry DMF is formed a stable, violet radical anion with a broad maximum at 682 nm 2,4,6-Triphenylaniline shows in CV in acetonitrile a reversible oxidation; in acetonitrile containing pyridine it is oxidized to azo(2,4,6-triphenylbenzene). This compound is in acidic aqueous DMF reduced to 2,4,6- triphenylaniline. The three phenyl groups act as electron donating groups during reductions akin to p-hydroxy or p-amino groups.

The Design of Metal Chelates with a Biologically Related Redox‐Active Part: Conjugation of Riboflavin to Bis(2‐pyridylmethyl)amine Ligand and Preparation of a Ferric Complex

AbstractReaction of a twofold molar excess of bis(2‐pyridylmethyl)amine DPA with 8α‐bromoAc4riboflavin in dry DMF over 24 h affords the 8α‐[bis(2‐pyridylmethyl)amine]‐N‐Ac4riboflavin ligand. This compound can be described as a tweezer in which the flavin moiety acts as a potential electron mediator. The trichloroferric complex has been prepared, and together with the low potential reduction wave of the flavin moiety, the presence of a reversible FeIII/FeII couple at a higher potential is observed. The deacetylated ligand 8α‐[bis(2‐pyridylmethyl)amine]‐N‐riboflavin can easily be obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Facile electrochemical transformation of diazonium salts into carboxylic acids

The electrolyses of aryldiazonium tetrafluoroborates in dry DMF and Bu 4NHSO 4 as solvent-supporting electrolyte system, in the presence of CO 2 led to the corresponding arylcarboxylic acids in very good yields.

Synthesis, characterization, and electrochemical, electrical and gas sensing properties of a novel tert-butylcalix[4]arene bridged bis double-decker lutetium(III) phthalocyanine

A novel tert-butylcalix[4]arene bridged bis double-decker lutetium(III) phthalocyanine (Lu 2Pc 4) ( 5) has been synthesized by the reaction of dimeric lutetium(III) phthalocyanine ( 4) with two equiv. of dilithium octakis hexylthiophthalocyanine in amyl alcohol. The phthalonitrile derivative 1 was obtained through the displacement reaction of 4-nitrophthalonitrile with 1,3-dimethoxy-4- tert-butylcalix[4]arene and was converted to the isoindoline derivative 2 by bubbling ammonia gas in dry MeOH. Compound 4 was prepared from 2, 4,5-bis(hexylthio)-1,2-diiminoisoindoline ( 3), and lutetium acetate in dry DMF. The new compounds and phthalocyanines were characterized by elemental analysis, IR, UV–Vis, 1H NMR, ESR and MALDI-TOF MS spectra. The electrochemical properties of 4 and 5 have been examined by cyclic voltammetry, and compared. Distinctive differences between the voltammetric behaviour of 4 and 5 were detected. These differences were compatible with the structures of the compounds. A detailed study of the effect of temperature on the d.c. conductivity and impedance spectra (40–10 5 Hz) of spin coated films of 4 and 5 at temperatures between 290 K and 420 K was carried out. By analyzing the d.c. electrical behaviour of the 5 film, it was found that the experimental data are described by a thermally activated conductivity dependence on temperature with an activation energy of 0.77 eV. The a.c. results give a power law behaviour, σ a.c. = A( T) ω s , in which the frequency exponent s decreases with temperature. The sensing behaviour of the film for the online detection of volatile organic solvent vapors was investigated by utilizing an AT-cut quartz crystal resonator. It was observed that the adsorption of the target molecules on the coating surface cause a reversible negative frequency shift of the resonator. Thus, a variety of solvent vapors can be detected by using the 5 film as sensitive coating, with sensitivity in the ppm and response times in the order of several seconds depending on the dipole moment of the organic solvent.

Lewis Base Catalyzed Mannich‐Type Reactions between Trimethylsilyl Enol Ethers and Aldimines

Lewis base catalyzed Mannich-type reaction between trimethylsilyl enol ethers and N-tosylaldimines is described. Nitrogen anions generated from amides or imides such as lithium benzamide or potassium phthalimide are found to be effective Lewis base catalysts in DMF at room temperature to afford the corresponding beta-amino carbonyl compounds in good to high yields; the oxygen anion generated from carboxylic acids such as lithium acetate was also found to be effective in dry DMF. The above-mentioned lithium acetate-catalyzed Mannich-type reaction between aldimines and various trimethylsilyl (TMS) enol ethers such as silyl ketene acetal proceeded smoothly even in water-containing DMF. Then, Lewis base catalyzed three-component Mannich-type reactions of TMS enol ether, tosylamide, and aromatic aldehyde having electron-withdrawing group such as p-nitrobenzaldehyde were investigated. The reaction proceeded smoothly to afford the corresponding beta-amino ester in good yield. Further, ammonium carboxylates such as tetrabutyl ammonium acetate or tetrabutyl ammonium benzoate were found to be more effective Lewis base catalysts in the above-mentioned Mannich-type reaction. The synthesis proceeded in various solvents at lower temperatures. The reaction between aldimines and TMS enol ethers generated from thioester and various ketones such as propiophenone or cyclohexanone also proceeded smoothly to afford the corresponding beta-amino carbonyl compounds in high yields with good to high anti-selectivities.

On the electrochemistry of 2,4,6-triphenylnitrobenzene and related compounds

Cyclic voltammetry at a glassy carbon electrode of 2,4,6-triphenylnitrobenzene (1) in DMF shows two reversible one-electron reductions. Preparative reduction of 1 yields 2,4,6-triphenylaniline under both acidic and alkaline conditions and in DMF in the presence of acetic anhydride. On reduction in dry DMF is formed a stable, violet radical anion with a broad maximum at 682nm; in acetonitrile 1 is reported to yield an unstable bluish radical which is transformed to a yellow-purple radical with a maximum at 520nm. Solid-state 13C NMR confirmed the existence of two stereoisomers in the crystals found by X-ray structure determination, whereas 13C NMR in chloroform at ambient temperature indicated one isomer in solution. 2,4,6-Triphenylaniline shows in CV in acetonitrile a reversible oxidation; in acetonitrile containing pyridine it is oxidized to azo(2,4,6-triphenylbenzene). This compound is in acidic aqueous DMF reduced to 2,4,6-triphenylaniline. The three phenyl groups act as electron donating groups during reductions akin to p-hydroxy or p-amino groups.

Pd-Catalyzed Ring Opening of Oxa- and Azabicyclic Alkenes with Aryl and Vinyl Halides: Efficient Entry to 2-Substituted 1,2-Dihydro-1-naphthols and 2-Substituted 1-Naphthols

An efficient syntheses of 2-substituted 1,2-dihydro-1-naphthols and 2-substituted 1-naphthols has been developed that involves the sequential palladium-catalyzed ring opening of oxabicyclic alkenes with aryl and vinyl halides followed by oxidation of with IBX. In the first step of the sequence, a combination of Pd(OAc)2, PPh3, Zn, and PMP in dry DMF was employed to catalyze the ring opening of 7-oxabenzonorbornadienes with aryl and vinyl halides to afford the corresponding cis-2-substituted 1,2-dihydronaphthols in good to excellent yields. These reactions occurred under very mild conditions with a variety of aryl halides bearing electron-withdrawing or -donating groups. Similarly, a 7-azabenzonorbornadiene substituted with an electron-withdrawing group on the nitrogen atom underwent facile ring-opening reaction with aryl halides to provide cis-2-substituted (1,2-dihydro-1-naphthyl)carbamates in excellent yields. Oxidation of the intermediate 1,2-dihydro-1-naphthols using IBX yielded the corresponding 2-substituted 1-naphthols in good to excellent yields.