Modified Ullmann Reaction Research Articles

Synthesis, characterisation and reactivity of copper(I) amide complexes and studies on their role in the modified Ullmann amination reaction.

A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide (1), copper(I) 2,2,6,6-tetramethylpiperidide (2), copper(I) pyrrolidide (3), copper(I) piperidide (4), and copper(I) benzylamide (5). Their solid-state structures and structures in [D6]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1, 2 and 4 are shown to exist as tetramers in the solid state by X-ray crystallography. In [D6]benzene solution, complexes 1, 2 and 5 were found by using 1H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 m concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one-dimensional 1H and 1H DOSY NMR spectroscopy. Complexes 3–5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10-phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol.

Synthesis, biological evaluation and Structure Activity Relationships (SARs) study of 8-(substituted)aryloxycaffeine

A series of 8-(substituted)aryloxycaffeine were prepared from 8-bromocaffeine and (substituted)phenols by modified Ullmann reaction. In vitro antibacterial activity, inhibitory activity on topoisomerase II and pharmacological activities were evaluated for the synthesized 8-(substituted)aryloxycaffeine. Among the synthesized compounds, 8-(5-chloropyridin-3-yloxy)caffeine (3k) showed strong inhibitory activity (MIC=15.6μg/mL) against the tested gram negative (−) bacteria Salmonella enteritidis. 8-(quinolin-8-yloxy)caffeine (3g) showed the strongest inhibitory activity against topoisomerase II. And the compounds 8-(6-methylpyridin-2-yloxy)caffeine (3j) and 8-(3-chloro-6-(trifluoromethyl)pyridin-2-yloxy)caffeine (3m) showed analgesic effect without the central nervous system stimulation.

A low temperature bottom-up approach for the synthesis of few layered graphene nanosheets via C–C bond formation using a modified Ullmann reaction

A low temperature, single-pot, bottom-up approach for the synthesis of few layered graphene sheets using the modified Ullmann reaction is reported.

Synthesis of Functionalized Acenaphthenes and a New Class of Homooxacalixarenes

The 5,6-dialkoxyethers of acenaphthene have been synthesized for the first time via modified Ullmann reaction conditions. Further modifications of the 5,6-dimethoxyacenaphthene allowed the synthesis of the first acenaphthene analogue of the octahomotetraoxacalixarenes. The X-ray structure of this new macrocycle and its complexation study with C(60) are reported.

Synthesis of spiro[fluorene-9,9′-xanthene] derivatives and their application as hole-transporting materials for organic light-emitting devices

A series of hole-transporting molecules based on spiro(fluorene-9,9′-xanthene) were designed and synthesized by a copper-catalyzed modified Ullmann reaction. These compounds have very high-lying HOMO levels (∼5.0eV), which are beneficial for the hole-injection from ITO anode. The double-layer EL devices using DPA-SFXMe and DPA-SFXBu as hole-transporting layers exhibit lower turn-on voltage and higher efficiency compared with those of a typical NPB-based device. The DPA-SFXBu-based device exhibits high maximum luminescence of 21,712cd/m2, and its power efficiency can reach a value of 2.31lm/W, which is nearly 90% higher than that of a similar NPB-based device.

Direct Guanidinylation of Aryl and Heteroaryl Halides via Copper-Catalyzed Cross-Coupling Reaction

A modified Ullmann reaction using p-methoxybenzyl (PMB) guanidine as guanidinylation agent yielded various aryl and heteroaryl guanidines in good yields.

ChemInform Abstract: The Mechanism of the Modified Ullmann Reaction

AbstractReview: 150 refs.

Synthesis and characterization of efficient luminescent materials based on 2,1,3-benzothiadiazole with carbazole moieties

Two new luminescent materials named 4-bromo-7-carbazyl-[2,1,3]-benzothiadiazole (3) and 4,7-dicarbazyl-[2,1,3]-benzothiadiazole (4) were obtained by a modified Ullmann reaction in one step from 4,7-dibromo-[2,1,3]-benzothiadiazole (2) (based on 2,1,3-benzothiadiazole (1, BTD)) and carbazole. The structure and purity of them were characterized by crystal structures, 1H NMR and elemental analysis. Compared with compounds 1 and 2, the compounds 3 and 4 have better optical properties and thermostability due to the introduction of the carbazole moieties, and the compound 4 shows better performances than that of compound 3. For compound 4, a strong absorption peak at 236 nm with a high extinction coefficient up to 1.205 × 10 5 L·mol·cm −1 and bright green to orange photoluminescence with quantum yields of 9.0%, 48.4%, 51.0% and 75.6% in different solvents of acetonitrile, dichloromethane, ethyl acetate, and diethyl ether, respectively, were measured.

ChemInform Abstract: 4‐Thio Derivatives of Dibenzosuberone: Potential Antidepressant Compounds.

AbstractTitle compounds are prepared by regioselective iodination with Tl(tfa)3/KI followed by a modified Ullmann reaction.

The mechanism of the modified Ullmann reaction

The copper-mediated aromatic nucleophilic substitution reactions developed by Fritz Ullmann and Irma Goldberg required stoichiometric amounts of copper and very high reaction temperatures. Recently, it was found that addition of relatively cheap ligands (diamines, aminoalcohols, diketones, diols) made these reactions truly catalytic, with catalyst amounts as low as 1 mol% or even lower. Since these catalysts are homogeneous, it has opened up the possibility to investigate the mechanism of these modified Ullmann reactions. Most authors agree that Cu(I) is the true catalyst even though Cu(0) and Cu(II) catalysts have also shown to be active. It should be noted however that Cu(I) is capable of reversible disproportionation into Cu(0) and Cu(II). In the first step, the nucleophile displaces the halide in the LnCu(I)X complex forming LnCu(I)ZR (Z = O, NR′, S). Quite a number of mechanisms have been proposed for the actual reaction of this complex with the aryl halide: 1. Oxidative addition of ArX forming a Cu(III) intermediate followed by reductive elimination; 2. Sigma bond metathesis; in this mechanism copper remains in the Cu(II) oxidation state; 3. Single electron transfer (SET) in which a radical anion of the aryl halide is formed (Cu(I)/Cu(II)); 4. Iodine atom transfer (IAT) to give the aryl radical (Cu(I)/Cu(II)); 5. π-complexation of the aryl halide with the Cu(I) complex, which is thought to enable the nucleophilic substitution reaction. Initially, the radical type mechanisms 3 and 4 where discounted based on the fact that radical clock-type experiments with ortho-allyl aryl halides failed to give the cyclised products. However, a recent DFT study by Houk, Buchwald and co-workers shows that the modified Ullmann reaction between aryl iodide and amines or primary alcohols proceeds either via an SET or an IAT mechanism. Van Koten has shown that stalled aminations can be rejuvenated by the addition of Cu(0), which serves to reduce the formed Cu(II) to Cu(I); this also corroborates a Cu(I)/Cu(II) mechanism. Thus the use of radical clock type experiments in these metal catalysed reactions is not reliable. DFT calculations from Hartwig seem to confirm a Cu(I)/Cu(III) type mechanism for the amidation (Goldberg) reaction, although not all possible mechanisms were calculated.

Well Defined Carbazol-3,9-Diyl Based Oligomers as Host Materials for Organic Electro-Phosphorescent Devices

Well defined carbazol-3,9-diyl-based derivatives as host materials for electro-phosphorescent devices have been synthesized by the modified Ullmann reaction as a key step. The full characterization of their structure by mass spectrometry, infrared absorption and proton magnetic resonance spectroscopy is presented. The amorphous compounds with glass transition temperatures of 103–154°C possess high thermal stability with onset decomposition temperatures exceeding 360°C. Conjugation of the 3,9-linked systems is rather confined within one carbazole unit, retaining large triplet energies suitable for green and red electro-phosphorescence. Using the new host material, efficient green phosphorescent organic light emitting diodes was demonstrated.

Synthesis and Characteristics of Hole-transporting Materials Based on Biphenyl Diamine Derivatives with Carbazole Groups

Two hole-transporting materials containing carbazole moieties with TPD- and NPB-like structures, 4,4′-bis [N-(4-carbazolylphenyl)-N-phenylamino] biphenyl (CPB) and 4,4′-bis [N-(4-carbazolylphenyl)-N-(1-naphthyl) amino]biphenyl(CNB), were synthesized via a modified Ullmann reaction. The resulting compounds were thermally stable with high glass transition temperatures ranging from 145 to 147 °C and possessed a good electrochemical reversibility and hole-transporting properties. Typical double-layer device evaluation with the structure ITO/CPB(40 run)/Alq3(60 nm)/LiF/Al demonstrated that they were promising hole-transporting materials with a current efficiency of 5. 25 cd/A and a power efficiency of 2. 00 lm/W.

Oligomeric cyanate ester resins: Application of a modified Ullmann synthesis in the preparation of thermosetting polymers

AbstractNew multiple aromatic ether containing oligomeric cyanate ester resins have been synthesized using a modified Ullmann reaction. The oligomeric monomers were prepared by reacting resorcinol and 1,3‐ or 1,4‐dibromobenzene in the presence of potassium carbonate and a catalytic amount of a copper(I) complex in a N,N‐dimethylformamide/toluene mixture. The hydroxyl terminated intermediates were end‐capped with the cyanate moiety by reaction with cyanogen bromide in the presence of triethylamine in dry acetone. The oligomeric cyanate ester monomers are liquid at room temperature, which enhance their processability to polymeric networks. The thermo‐oxidative properties were determined for the new cyanate ester polymers as well as their storage modulus. The length of the aromatic ether spacer between the terminal cyanate ester groups was varied to investigate the effect of changing the spacer length on the properties of the material. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4559–4565, 2006

Novel hyperbranched poly(phenylene oxide)s with phenolic terminal groups: synthesis, characterization, and modification

Novel hyperbranched poly(phenylene oxide)s (HPPOs) with phenolic terminal groups were prepared from 4-bromo-4′,4″-dihydroxytriphenylmethane via a modified Ullmann reaction. This monomer was treated with potassium carbonate or sodium hydroxide as a base and copper chloride as a catalyst in an aprotogenic solvent, either dimethylsulphoxide (DMSO) or sulfolane. The sulfolane/NaOH system at higher temperature led to more rapid polymerization, and a relative high molecular weight. The degrees of branching of these HPPOs from the DMSO/K 2CO 3 and sulfolane/NaOH systems were 71 and 48%, respectively, as determined by 1H NMR integration experiments. The phenolic terminal groups underwent facile modification, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain-end groups had a significant influence on the solubility of the hyperbranched poly(phenylene oxide)s. The resulting polymers were characterized by NMR, Fourier transform infrared, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).

Well defined carbazole-based hole-transporting amorphous molecular materials

Monodisperse carbazole-based oligomers have been synthesized via C N bonds formation by the modified Ullmann reaction. The full characterization of their structure is presented. These derivatives are highly thermally stable amorphous compounds with glass transition temperatures of 167–171 °C and thermal decomposition temperatures of ca. 400 °C. Amorphous films of the materials were fabricated and their hole-transporting properties were tested in a light emitting device with Alq 3 as an electroluminescent and electron-transporting material.

Blue light-emitting materials based on terfluorenes with carbazole terminal units

Three thermally stable ter(9,9-disubstitutedfluorene)s with hole-transporting carbazole moieties at two terminals ( DCTFs) have been synthesized by modified Ullmann reaction and Pd-catalyzed Suzuki coupling. The resulting compounds are amorphous with glass transition temperature ( T g) in the range of 201–205 °C. The electroluminescence efficiency up to 1.6 cd/A has been achieved with the device structure of ITO/NPB (30 nm)/ DCTF-3(30 nm)/BCP (20 nm)/Alq 3 (30 nm)/LiF/Al. A 60% increase of efficiency along with the CIE coordinates of (0.16, 0.11) was demonstrated compared with terfluorene ( TF) analogue based device.

Well defined carbazol-3,9-diyl based oligomers with diphenylamino end-cap as novel amorphous molecular materials for optoelectronics

Well defined carbazol-3,9-diyl-based oligomers of new type have been synthesized by the modified Ullmann reaction starting from 3-iodo-9H-carbazole and diphenylamine. The full characterization of their structure is presented. The amorphous compounds with glass transition temperatures of 111–162 °C possess high thermal stability with onset decomposition temperatures of 320–380 °C. Amorphous films of the materials were fabricated by vacuum evaporation. They were used for the preparation of multilayer electroluminescent devices.

Phenothiazinyl-containing aromatic amines as novel amorphous molecular materials for optoelectronics

Novel aromatic amines have been synthesized by the modified Ullmann reaction of 10H-phenothiazine and di(4-iodophenyl)ethylamine or 3,6-diiodo-9-hexylcarbazole. The full characterization of their structure is presented. The compounds possess high thermal stability with glass transition temperatures of 87–103 °C and onset decomposition temperatures of 346–377 °C. Room temperature hole drift mobilities in amorphous films of the materials were, respectively, 1.2 × 10 −6 and 2 × 10 −5 cm 2/V s at an applied electric field of 3.6 × 10 5 V/cm. The electron photoemission spectra of the molecular glasses have been recorded and the ionisation potentials of 5.5–5.54 eV have been established. The values obtained have been compared with the values of ionisation potential of photoconductive oligomers containing unsubstituted carbazolyl or diphenylamino groups.

Carbazole-based hole-transporting materials for electroluminescent devices

Two kinds of carbazole-based molecules connected with diphenylamine and carbazole are synthesized by modified Ullmann reaction. Comparative study on their thermal stability, redox behavior, hole injection and transport properties are present. The results demonstrate that the carbazole-based molecules are very promising hole-transporting materials for electroluminescent devices.

Novel deep blue fluorescent fluorene-based copolymer containing hole-transporting arylamine segments

A novel conjugated copolymer-poly((9,9-dioctylfluorene)- alt-( N, N′-diphenylbenzidine)), bearing an arylamine moiety in the polymer backbone, has been synthesized by a modified Ullmann reaction. The new polymer can be easily dissolved in common organic solvents and form uniform thin films. The NMR and FT-IR spectra showed that it has a well-defined structure. Thermogravimetric analyses and differential scanning calorimetry analyses indicated that the polymer exhibits good thermal stability with the onset decomposition temperature in nitrogen at 300 °C and a glass-transition temperature ( T g) at 148 °C. The UV and photoluminescence spectra of the film samples indicate that the polymer has a band gap of 2.83 eV and deep blue light-emission. Cyclic voltammetry illustrated that the polymer can be reversibly p-doped and dedoped at rather low oxidative potential compared with poly(dialkylfluorene), implying that the new polymer has better hole-transporting property. All the results demonstrate that the obtained polymer is a promising deep blue light emission or hole-transporting material for PLED applications.