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A bidirectional Pictet-Spengler Reaction allows easy access to nitrogen-rich aromatics with seven fused rings. Photophysical measurements and computational methods show significant differences to parent N-heteropolycycles with fewer nitrogen atoms.

Multisubstituted alkenes are accessible by a gold-catalyzed acyloxyalkynylation of ynamides with ethynylbenziodoxolones (EBXs) with perfect atom-economy. The EBX reagents transfer both the carboxylate as well as the alkynyl entity. Overall, this cascade comprises the in situ generation of an alkynyl gold(III) species, a stereoselective C(sp)-C(sp

The synthesis of π-extended pyrene-based luminescent compounds containing two six-membered phosphacycles has been realized through a two-step synthesis. It involves a Cu(II)-mediated double cyclization of tertiary diphosphane derivatives to afford dicationic molecules with quaternized phosphorus centers. Subsequent transformation of diphosphonium species into the corresponding P-oxide derivatives has been successfully achieved through Pd(0)-assisted cleavage of the P-Ph bonds, which opens a promising way for the functionalization of polyaromatic P-systems.

A strongly twisted benzo-fused tris-cycloheptenylene, containing three dibenzosuberenone units fused to a common benzene ring, was subjected to Ramirez olefination and subsequent palladium-catalyzed Suzuki-Miyaura cross-coupling with 4-substituted phenylboronic acids. The high steric demand within the overcrowded, benzene-rich benzo-fused tris-cycloheptenylenes enforced an unprecedented 1,2-rearrangement upon π-extension during the Suzuki coupling reaction. According to crystal structure analysis, the resulting negatively curved polycyclic aromatic hydrocarbons consist of two heptagons and one octagon surrounding a central benzene ring as a result of strain release. In the solid state, the materials exhibit a blue to blue-green fluorescence with increased quantum yields and a hypsochromic shift of the emission maxima compared to their respective solutions.

A novel ring-opening reaction of donor–acceptor cyclopropanes (DACs) through a one-pot three-component nucleophilic addition of amines, CS2, and DACs has been described. New γ-dithiocarbamate dialkyl malonate skeletons were obtained in up to 97% yield.

An efficient strategy for the synthesis of functionalized 1-aminoisoquinoline derivatives has been developed through the reaction of o-alkynylbenzaldoximes with 2H-azirines using electrophiles.

The synthesis of novel (N-)acene-based cyclooligomers is reported. Glaser-Hay coupling of the bisethynylated monomers results in cyclodimers and cyclotrimers that are separable by column and gel-permeation chromatographies. For the diazatetracene, the use of sec-butyl-silylethynyl groups is necessary to achieve solubility. Diazatetracene-based cyclodimers and cyclotrimers were used as semiconductors in thin-film transistors. Although their optoelectronic properties are quite similar, their electron mobilities in proof-of-concept thin-film transistors differ by an order of magnitude.

A transition-metal-free postmodification of the Groebke-Blackburn-Bienayme (GBB) reaction for the synthesis of spiro[chromene-imidazo[1,2-a]pyridin]-3'-imine was discovered. The unusual transformation represents the first example of activation and the reaction of the imidazole carbon atom. In this postcondensational modification, KOt-Bu acts as a base, which, after the isomerization of an alkyne moiety to allene, causes the next unique nucleophilic reaction of the imidazole carbon atom that results in spirocyclic structures. The proposed reaction mechanism was confirmed based on the DFT calculations.

Herein, we describe a gold‐catalyzed cascade cyclization of Boc‐protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6‐endo‐dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc‐protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π‐extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields. Two bidirectional approaches under the optimized conditions were successful, and the resulting π‐extended molecules were tested as organic semiconductors in organic thin‐film transistors., Suitable substitution: The synthesis of highly substituted six‐membered N‐heterocycles using gold catalysis is reported. The applied cascade reaction using different substituted alkyne systems as starting materials furnished the corresponding benzo[c]phenanthridines in very high overall yields. In addition, two π‐extended molecules were studied as organic semiconductors in organic thin‐film transistors.

Practical Pd-catalyzed 2-pyridones were designed to achieve chromeno[2,3-b]pyridine-2-ones. The reaction proceeds through domino nucleophilic addition and decarboxylative arylation, respectively. This methodology offers a moderately efficient approach to construct the bioactive, fused-heterocyclic skeletons via selective C-O bond formation and decarboxylative arylation in a single step with high selectivity and good yields.

Quinoxalinophenanthrophenazines (QPPs) and related structures are an emerging class of stable fused N-heteropolycyclic aromatics. By vertical attachment of aromatic substituents at the pyrene core, cruciform QPPs are accessible, which open new opportunities to adjust HOMO and LUMO levels of the QPPs nearly independent from each other. A series of cruciform aryl-substituted quinoxalinophenanthrophenazine derivatives (QPPs) was synthesized through Suzuki-Miyaura cross-coupling of a 2,7-diborylated pyrene tetraketal building block. The QPPs were analyzed for their optoelectronic properties by absorption and emission spectroscopy, cyclic voltammetry and quantum-chemical calculations. The solid-state packing was investigated as well and evaluated for its charge transport properties by calculated charge transfer integrals.

Fused polycyclic aromatic compounds are interesting materials for organic electronics applications. To fine‐tune photophysical or electrochemical properties, either various substituents can be attached or heteroatoms (such as N or S) can be incorporated into the fused aromatic backbone. Coronenes and heterocoronenes are promising compounds in this respect. Up until now, the possibilities for varying the attached fused heteroaromatics at the coronene core were quite limited, and realizing both electron‐withdrawing and ‐donating rings at the same time was very difficult. Here, a series of pyridine, anisole and thiophene annulated tetraareno[a,d,j,m]coronenes has been synthesized by a facile two‐step route that is a combination of Suzuki‐Miyaura cross‐coupling and a following cyclization step, starting from three different diarenoperylene dibromides. The contorted molecular π‐planes of the obtained cata‐condensed tetraarenocoronenes were analyzed by single‐crystal X‐ray crystallography, and the photophysical and electrochemical properties were systematically investigated by UV/Vis spectroscopy and cyclovoltammetry., Tuning tetraarenocoronenes: Cata‐condensed heteroannulated tetraarenocoronenes with C 2h symmetry have been obtained from three doubly brominated diarenoperylenes. X‐ray diffraction showed that the coronenes mostly adopt S‐shaped contorted π‐planes. The large variety of fused rings in the coronenes′ core allows good control of their photophysical properties and thus their potential use in organic electronics applications.

Four N-acenoacenes were synthesized and analyzed for their optoelectronic properties and solid-state packings. Two of the regioisomeric acridinoacridines are TIPS-ethynylated, whereas the other pair are Boc- and triflate substituted derivatives. The two TIPS-ethynyldiazaacenoacenes were processed into organic thin-film transistors with saturation hole mobilities reaching 2.9×10

We describe a novel and efficient synthetic strategy to construct the linear homoallylic quinolone structures through the intermolecular addition of 2-alkynylquinoline toiN/i-allenyl sulfonamides. We developed the regio- and diastereoselective transition metal-free hydroalkylation of 1,2-dienes by a structure containing a push-pull system. Moreover, the present work was carried out with a high atom economy, mild reaction conditions, and moderate to high yields.

A novel doubly cyclopentannulated carbazole which is accessible through a successive π-expansion of di(1-naphthylamine) is disclosed. The carbazole moiety is generated in the final step through intramolecular oxidative coupling. The π-expansion of carbazole resulted in strongly altered optoelectronic and electrochemical properties. The solid-state structure features an interesting packing motif with alternating face-to-face π⋅⋅⋅π and edge-to-face C-H⋅⋅⋅π interactions. The experimental findings were corroborated by theoretical calculations.

A novel, benign synthetic strategy towards soluble tetra(peri‐naphthylene)anthracene (TPNA) decorated with triisopropylsilylethynyl substituents has been established. The compound is perfectly stable under ambient conditions in air and features intense and strongly bathochromically shifted UV/vis absorption and emission bands reaching to near‐IR region beyond 900 nm. Cyclic voltammetry measurements revealed four facilitated reversible redox events comprising two oxidations and two reductions. These remarkable experimental findings were corroborated by theoretical studies to identify the TPNA platform a particularly useful candidate for the development of functional near‐IR fluorophores upon appropriate functionalization.

Brominated pentannulated dihydrotetraazapentacenes were prepared by gold- or palladium-catalyzed 5-endo-dig cyclization of TIPS-ethynylated dihydrotetraazaacenes (TIPS = triisopropylsilyl). Post-functionalization was demonstrated by Sonogashira alkynylation and Rosenmund-von Braun cyanation. Calculations predict these species to act as n-type semiconductors, which was verified for two derivates through characterization in organic field-effect transistors.

A regio- and diastereoselective ring-expansion reaction of N-acylaziridines is described for the synthesis of 4-carboxamide oxazolines using InCl3. A domino Ugi–Joullié/ring-expansion reaction of arylphenylazirines, isocyanides, and carboxylic acids leads to the target products through the N-acylaziridine intermediates in the presence of the indium catalyst. The oxazolines were synthesized in moderate to excellent yields with high atom economy and high bond-forming efficiency under mild reaction conditions.

A gold-catalyzed synthesis of tetrasubstituted 1,3-enynes from hypervalent iodine(III) reagents and activated alkenes is reported. This reaction involves an in situ formed alkynyl Au(III) species and a subsequent direct C(sp2)-H functionalization of alkenes, offering 26 enynes in 62-92% yield with excellent functional group tolerance.

The syntheses, properties and application of the air‐stable electron acceptors, diindenopyrazines 4 a–g are reported demonstrating the introduction of functional aryl groups in the 6‐ and 12‐positions. The targets are accessible on the hundred milligram to gram scale. The structure of the aryl groups in 4 a–g modulates their solubility, redox potentials and optical properties. The introduction of electron‐poor aryl groups to the electron‐poor diindenopyrazine backbone reduces the electron affinity to −4 eV, making the compounds attractive as n‐semiconductors. A simple organic field‐effect transistor of 4 e –without optimization– shows electron transport with a mobility of up to 0.037 cm2 V−1 s−1., Electron poor, but rich in possibility: Electron‐deficient diindenopyrazines with different aryl substituents have been synthesized and characterized. The introduction of electron‐poor aryl groups reduces the electron affinity to −4 eV, thereby making the compounds attractive as n‐semiconductors. Tested in an organic field‐effect transistor, compound 4 e showed electron mobilities up to 0.037 cm2 V−1 s−1.

Starting from commercially available DMSAuCl and diazonium salts, cationic [ N∧C∧N ]AuIII complexes were synthesized in a selective, photosensitizer-free, photochemical reaction by irradiation with blue LED light. This new protocol represents the first easy synthesis of these types of pincer complexes in moderate to excellent yield starting from a readily available gold(I) precursor with nitrogen as the only by-product. Owing to the disadvantages of known protocols, especially the toxicity in the case of a transmetalation with mercury or the necessity for a mostly twofold excess of a gold precursor, this method offers an attractive alternative towards this kind of gold(III) complexes. In addition, the first arylated [ N∧C∧N ]Au(III) pincer complex was synthesized by using this technology.

The synthesis of two diazabisacenes is reported. A bisboronated naphthalene was Suzuki‐coupled to substituted ethyl nicotinates, then cyclized by intramolecular Friedel‐Crafts acylation. The resulting diketones were alkynylated and reduced to give the title compounds, bis(TIPS‐ethynyl)‐substituted naphtha[1,8‐gh:5,4‐g′h′]diquinoline and naphtho[1,8‐bc:5,4‐b′c′]diacridine. Nitrogen incorporation stabilizes the bisacenes with respect to oxidation compared to their consanguine nonaza analogs., Gluing together two monoazaacenes: The synthesis of two novel diazabisacenes with cata‐annelated monoazaacene subunits sharing three joint bonds is reported. These “π‐extended pyrenes” exhibit global aromaticity with bond length alternations and optical spectra similar to acenes, thus justifying the term “bisacenes” for the compounds investigated. Introducing nitrogen into the bisacene backbone significantly increases stability compared to that of their hydrocarbon analogs.

The pollution of groundwater with nitrate is a serious issue because nitrate can cause several diseases such as methemoglobinemia or cancer. Therefore, selective removal of nitrate by efficient binding to supramolecular hosts is highly desired. Here we describe how to make [2+3] amide cages in very high to quantitative yields by applying an optimized Pinnick oxidation protocol for the conversion of corresponding imine cages. By NMR titration experiments of the eight different [2+3] amide cages with nitrate, chloride and hydrogen sulfate we identified one cage with an unprecedented high selectivity towards nitrate binding vs. chloride (S=705) or hydrogensulfate (S13500) in CD

We disclose a successive π-expansion of pyracylene towards boat-shaped polycyclic scaffolds. The unique structural features of the resulting compounds were revealed by X-ray crystallographic analysis. Depending on the extent of π-expansion the compounds display intense bathochromically shifted absorption bands in their UV/Vis spectra and are prone to several redox events as documented by cyclic voltammetry. The experimental observations are in line with the computational studies based on density functional theory, suggesting progressive narrowing of the HOMO-LUMO gap and distinct evolution of the electronic structure and aromaticity.

Tetraiodotetraazapentacene I

Chemistry - a European journal e202201816 (2022). doi:10.1002/chem.202201816, Published by Wiley-VCH, Weinheim

A family of fully bridged triphenylamines with embedded 5‐ and 7‐membered rings is presented. The compounds are potent electron donors capable to undergo donor/acceptor interactions with strong cyano‐based acceptors both in the solid state and solution. These interactions were evaluated by IR and UV/vis spectroscopy as well as X‐ray crystallography. The vinylene‐bridged compound was oxidized to the corresponding 1,2‐diketone which readily underwent acid‐catalyzed condensation with selected 1,2‐phenylenediamines. The resulting π‐extended quinoxaline derivatives represent valuable building blocks for the development of functional chromophores upon appropriate functionalization.

In this project, a moderately efficient approach to multisubstituted N-(isoquinolin-1-yl)sulfonamide derivatives was illustrated, utilizing ortho-alkynylbenzaldoximes and zwitterionic ketenimine salts in a tandem reaction catalyzed by silver oxide. The oxophilicity of Ag2O, along with its nature as Lewis acid, pave the way for a smooth [3 + 2] cycloaddition between isoquinoline N-oxides and ketenimine species, which is a key step in this reaction. DFT calculation suggests that 1,3-dipolar cycloaddition of nitrone and ketenimine proceeds through a selective stepwise mechanism.

Bis(silylethynylated) 5,7‐ and 5,12‐diazapentacenes were synthesized from cis‐ and trans‐quinacridone using protection, alkynylation and deoxygenation. The solid‐state packing of the targets is determined by choice and position of the silylethynyl substituents. The position of the substituents and nitrogen atoms influence the optical properties of the targets., Piecing together a diazaacene: Starting from linear cis‐ and trans‐quinacridones, the synthesis, characteristics and stability of four diazapentacenes are reported leading to a design rule for 12,14‐alkynylated heteroacenes for organic electronics (see figure).