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4-Alkylpyridines are converted into conjugated 1,1-disubstituted alkenyl pyridines (vinyl pyridines) upon treatment with excess ethyl chloroformate, triethylamine, and Eschenmoser’s salt. The reaction proceeds under mild conditions via alkylidene dihydropyridine intermediates.

Aldehyde-derived imidazolidines participate as hydride donors in intramolecular reductive Heck-type reactions.

An experimentally simple one-pot preparation of N-alkenyl-2-pyridones is reported. The reaction features mild conditions using readily available 2-halopyridinium salts and aldehydes. N-Alkenyl-2-pyridone formation proceeds with high diastereoselectivity, and a wide range of aldehyde reaction partners is tolerated. Pyridone products are also amenable to further manipulation, including conversion to N-alkyl pyridones and polycyclic ring systems.

An experimentally simple one-pot preparation of N-alkenyl-2-pyridones is reported. The reaction features mild conditions using readily available 2-halopyridinium salts and aldehydes. N-Alkenyl-2-pyridone formation proceeds with high diastereoselectivity, and a wide range of aldehyde reaction partners is tolerated. Pyridone products are also amenable to further manipulation, including conversion to N-alkyl pyridones and polycyclic ring systems.

Dihydroartemisinin (DHA) is an FDA-approved antimalarial drug that has been repurposed for cancer therapy because of its preferential antiproliferative effects on cancer versus normal cells. Mitochondria represent an attractive target for cancer therapy based on their regulatory role in proliferation and cell death. This study investigates whether DHA conjugated to innately fluorescent N-alkyl triphenylvinylpyridinium (TPVP) perturbs mitochondrial functions resulting in a differential toxicity of cancer versus normal cells. TPVP-DHA treatments resulted in a dose-dependent toxicity of human melanoma and pancreatic cancer cells, whereas normal human fibroblasts were resistant to this treatment. TPVP-DHA treatments resulted in a G(1)-delay of the cancer cell cycle, which was also associated with a significant inhibition of the mTOR-metabolic and ERK1/2-proliferative signaling pathways. TPVP-DHA treatments perturbed mitochondrial functions, which correlated with increases in mitochondrial fission. In summary, TPVP mediated mitochondrial targeting of DHA enhanced cancer cell toxicity by perturbing mitochondrial functions and morphology.

Probes for monitoring aggregation of amyloid beta (Aβ) peptides are crucial to advance understanding of the molecular pathogenesis of Alzheimer's Disease (AD). Here, we report luminescent tricarbonyl rhenium complexes of tetraarylethylene (TAE) ligands featuring bis(benzothiazole) chelating groups in combination with (oligo)thiophene units that have been designed for monitoring amyloid fibrillation. Variation in the number of thiophenes influenced the photophysical properties of these complexes, as well as their binding affinities toward Aβ42 fibrils. All complexes displayed submicromolar Kd's for binding Aβ42 aggregates accompanied by up to 34-fold enhanced luminescence and red-shifted emission wavelengths. The high binding affinities and desirable photophysical properties of these complexes render them potential alternatives to established fluorescent Aβ probes such as thioflavin T. Additionally, the general and modular design approach implemented in this study should facilitate development of second-generation TAE-based diagnostic tools for studying protein aggregation in AD and other neurological diseases.

Acylation of 4-alkylpyridines with 2-iodobenzoyl chlorides under basic conditions results in pyridine dearomatization via formation of 4-alkylidene dihydropyridines. These reasonably stable intermediates are further transformed through Pd-catalyzed Mizoroki–Heck cyclization to afford dihydropyrido-fused isoindolinone products in good yield. This study demonstrates successful harnessing of reactive dearomatized pyridine anhydrobases in metal-catalyzed C–C bond-forming reactions, and provides an efficient entry to isoindolinone ring systems structurally related to several indolizidine alkaloid frameworks.

Fluorescent sensors for Hg2+ that combine aggregation-induced emission (AIE) activity of tetraarylethylenes with metal chelating 1,1-bis(2-pyridylethylene) fragments and thiophene/bithiophene substituents have been prepared and characterized. The sensors exhibit red-shifted and enhanced emission in the presence of Hg2+ in aqueous solution while exhibiting little to no change in fluorescence in the presence of other metal ions. Job plot analyses indicate 2 : 1 sensor : Hg2+ binding stoichiometries in solution. 1H-NMR spectroscopy was also employed to investigate solution phase binding interactions between the sensors and Hg(ClO4)2, and a chelated HgI2–bis(pyridyl) complex has been characterized by X-ray crystallography. The limit of detection for Hg2+ was determined to be 48 nM. In contrast, the fluorescence of structurally analogous materials possessing quinoline rings in place of pyridine groups is completely quenched in the presence of Hg(ClO4)2. The high sensitivity and selectivity displayed by these sensors for Hg2+ over other metal ions may enable monitoring of mercury in aqueous environments.

The synthesis and photophysical properties of luminescent Re(i) tricarbonyl complexes prepared from bis(pyridyl)- and bis(quinolyl) tetraarylethylene (TAE) ligands are reported. Emission wavelengths of the complexes are influenced by structural variation in the tetraarylethylene ligands, and several complexes display aggregation-induced enhanced emission in aqueous solution. A Re(i) complex prepared from an indole-functionalized TAE ligand shows significant enhancement in its luminescence intensity accompanied by a remarkable blue shift (∼95 nm) upon specific binding to site II of human serum albumin.

Alkylidene dihydropyridines (anhydrobases) prepared via dearomatization of N-acylated 4-(aminomethyl)pyridines participate in [3 + 2] cyclocondensation reactions with aryldiazonium cations to afford substituted 1,2,4-triazolium salts or neutral 1,2,4-triazoles in high isolated yield. The reaction proceeds in the presence of a variety of N-acyl groups and aryl-susbtituted diazonium salts and offers a general route to pyridyl-substituted 1,2,4-triazoles.

Metastatic melanoma is the most aggressive and lethal form of skin cancer. Emerging evidence suggests that differences in melanoma metabolism relative to nonmalignant cells represent potential targets for improved therapy for melanoma. Specifically, melanoma cells exhibit increased mitochondrial electron transport chain (ETC) activity and concomitant hyperpolarized mitochondrial membrane potential relative to nonmalignant cells. We have synthesized several new fluorescent lipophilic vinylpyridinium cations built from tetraarylethylene scaffolds that target mitochondria via attraction to the hyperpolarized mitochondrial membrane potential. Mitochondria-specific accumulation in melanoma cells relative to normal human fibroblasts was demonstrated using confocal fluorescence microscopy and resulted in the disruption of oxidative metabolism leading to melanoma specific cell death in vitro. Thus, the pyridinium tetraarylethylene platform represents a promising new mitochondrial-targeted delivery vehicle with potential imaging and therapeutic properties.

Results of model studies demonstrating a stereoselective synthetic route to tricyclic analogues of the bis(piperidine) alkaloid xestoproxamine C are presented. Dearomatization of a tricyclic pyridine derivative to afford an alkylidene dihydropyridine (anhydrobase) intermediate followed by catalytic heterogeneous hydrogenation was used to install the correct relative stereochemistry about the bis(piperidine) ring system. Other key features of these model studies include development of an efficient ring-closing metathesis procedure to prepare macrocyclic derivatives of 3,4-disusbstituted pyridines, intramolecular cyclizations of alkylidene dihydropyridines to establish pyridine-substituted pyrrolidines and piperidines, successful homologation of pyridine-4-carboxaldehydes using formaldehyde dimethyl thioacetal monoxide (FAMSO), and application of B-alkyl Suzuki coupling to assemble substituted pyridines.

4-Substituted pyridines linked to iodoarene groups with alkyl amide tethers can be converted to the corresponding alkylidene dihydropyridines by treatment with ethyl chloroformate and Et3N. Subsequent exposure to Pd-catalyzed Mizoroki–Heck reaction conditions results in efficient intramolecular cyclization at the exocyclic alkene to afford isoindolinone and oxindole derivatives. Asymmetric construction of 3,3-disubstituted oxindoles and isoindolinones has also been achieved. This work demonstrates the ability to utilize reactive pyridine anhydrobases in metal-catalyzed transformations and provides the basis for design of new approaches to important heterocyclic ring systems.

Deficiencies in DNA mismatch repair (MMR) machinery result in greater incidence of DNA base pair mismatches in many types of cancer cells relative to normal cells. Consequently, luminescent probes capable of signaling the presence of mismatched DNA hold promise as potential cancer diagnostic and therapeutic tools. In this study, a series of cyclometalated platinum(II) complexes with sterically expansive tetraarylethylene ligands were synthesized and examined for selective detection of mismatched DNA. Increased steric bulk of the tetraarylethylene ligands in these complexes was observed to correlate with greater preferential luminescence enhancement in the presence of hairpin DNA oligonucleotides containing a mismatched site compared to well-matched oligonucleotides, with the most effective complex displaying ∼14-fold higher emission upon binding CC mismatched oligonucleotides compared to well-matched oligonucleotides. The results indicate binding to mismatched sites in DNA oligonucleotides occurs through metalloinsertion, and the luminescence response increases as a function of thermodynamic destabilization of the mismatch. Luminescence quenching experiments with Cu(phen)

Ten N-halophenylpyridinium salts (halogen = Br or I) with chloride (and in one case iodide) counterions have been prepared and structurally characterized in order to examine the degree of solid state halogen bonding exhibited in these systems. N-Halophenylpyridinium salts are easily synthesized from existing pyridines, and the cationic pyridinium group is expected to increase the halogen bond donor ability of attached halophenyl moieties. Halide anions functioning as halogen bond acceptors facilitate formation of charge-assisted halogen bonds. All five substrates featuring iodophenyl or diiodophenyl substituents displayed the expected halogen bonding interactions. In several cases halide ion acceptors were also engaged in complementary hydrogen bonding interactions with C–H groups of pyridinium rings and O–H groups of water solvates. Halogen bond donors containing a diiodophenyl group formed either an extended network or discrete supramolecular macrocyclic constructs through ArI···Cl–···IAr bridging inter...

1,2-Dialkylimidazoles can be converted to nucleophilic 2-alkylidene imidazolines upon treatment with (BOC)2O under mild conditions. Incorporation of a β-keto amide carbonyl electrophile in the 2-alkylimidazole side chain results in intramolecular aldol-like cyclization to afford imidazole-functionalized γ-lactams. Positioning of a ketone electrophile in a 1-alkyl side chain results in cyclization at the 2-position to afford fused ring imidazoles through a similar reaction manifold. Efficient transfer of a BOC group from an intermediate N-acyl imidazolium species to a nucleophilic center in the cyclized product appears to be an important feature of these reactions.

A new tetradentate polypyridine ligand that displays aggregation induced emission (AIE) characteristics has been synthesized. A coordination complex with CoCl2 has been prepared and characterized by X-ray crystallography. The Co(II) complex retains the AIE activity of the ligand in aqueous solution while also exhibiting a selective turn-on fluorescence response in the presence of cyanide anion. A complex : CN− binding stoichiometry of 1 : 2 was indicated via Job plot analysis and the limit of detection for CN− was determined to be 0.59 μM. The fluorescence response is attributed to coordination of CN− by the AIE active Co(II) complex, resulting in decreased solubility in aqueous medium and concomitant generation of larger nanoaggregates as revealed by dynamic light scattering (DLS) measurements. The sensitivity and selectivity displayed by this sensor for CN− over other anions renders it a candidate probe for CN− detection in aqueous environments.

Tetraarylethylene derivatives are emerging as an increasingly important family of supramolecular building blocks in both solution phase and the solid state. The utility of tetraarylethylenes stems from appealing structural features (rigidity and symmetry) and their propensity to exhibit aggregation induced emission (AIE). In an effort to investigate the luminescent sensing ability of heteroaromatic tetraarylethylenes, we previously prepared tetra(4-pyridyl)ethylene and characterized its solution phase AIE properties. We here report the successful incorporation of tetra(4-pyridyl)ethylene into three distinct salts and co-crystalline assemblies with three organic di-carboxylic acids (oxalic acid, malonic acid, and fumaric acid). Interactions between the tetra(pyridyl)ethylene and di-acid components were found to vary from conventional to charge-assisted hydrogen bonding according to the extent of proton transfer between the acid and pyridine groups. Notably, the formation of pyridinium-carboxylate adducts in the salts does not appear to be strongly correlated with acid pKa. Three distinct network topologies were observed, and all featured the bridging of two or three tetra(pyridyl)ethylene groups through di-acid linkers. Crystalline assemblies also retained the AIE activity of tetra(pyridyl)ethylene and were luminescent under UV light. As tetra(4-pyridyl)ethylene features four Lewis basic and potentially metal ligating pyridine rings in a relatively well-defined geometry, this compound represents an attractive building block for the design of additional crystalline organic and metal–organic functional materials.

Aggregation-induced emission (AIE) is emerging as an important design element in a variety of new fluorescent-based chemical sensors and bio-imaging agents. In particular, derivatives of tetraphenylethylene (TPE) have been widely utilized in this regard as the TPE framework is a reliable AIE-luminogen. To expand the library of AIE active tetraarylethylenes, we have explored the effects of replacing one or two of the phenyl rings in TPE with pyridine. Efficient synthetic routes that deliver mono- and bis-pyridyl tetraarylethylenes have been developed and the luminescent properties of these heterocyclic TPE analogues, along with their corresponding N-methylated pyridinium salts, have been examined.

Substituted tetraphenylethylenes (TPEs) have been prepared that feature four alkyl or aryl urea groups arrayed along the periphery. Exposure of these TPEs to monovalent anions (halide, carboxylate, nitrate, and azide) resulted in enhanced fluorescence emission attributed to aggregation of the TPE molecules via urea-anion hydrogen bonding. Emission enhancement correlated with anion basicity, with fluoride ion eliciting the largest fluorescence response. Increased fluorescence emission could also be detected visually in solutions viewed under UV light. This study demonstrates the feasibility of TPE-based fluorescent anion sensors/detectors, and it is envisioned that additional design modifications may afford anion-selective fluorescent sensors.

Switchable luminescent bioprobes whose emission can be turned on as a function of specific enzymatic activity are emerging as important tools in chemical biology. We report a promising platform for the development of label-free and continuous enzymatic assays in high-throughput mode based on the reversible solvent-induced self-assembly of a neutral dinuclear Pt(II) complex. To demonstrate the utility of this strategy, the switchable luminescence of a dinuclear Pt(II) complex was utilized in developing an experimentally simple, fast (10 min), low cost, and label-free turn-on luminescence assay for the endonuclease enzyme DNAse I. The complex displays a near-IR (NIR) aggregation-induced emission at 785 nm in aqueous solution that is completely quenched upon binding to G-quadruplex DNA from the human c-myc oncogene. Luminescence is restored upon DNA degradation elicited by exposure to DNAse I. Correlation between near-IR luminescence intensity and DNAse I concentration in human serum samples allows for fast and label-free detection of DNAse I down to 0.002 U/mL. The Pt(II) complex/DNA assembly is also effective for identification of DNAse I inhibitors, and assays can be performed in multiwell plates compatible with high-throughput screening. The combination of sensitivity, speed, convenience, and cost render this method superior to all other reported luminescence-based DNAse I assays. The versatile response of the Pt(II) complex to DNA structures promises broad potential applications in developing real-time and label-free assays for other nucleases as well as enzymes that regulate DNA topology.

4-Alkylpyridines functionalized with alkynyl amide substituents can be converted to pyridyl-substituted lactams via Au-catalyzed cyclization at the pyridine benzylic carbon. These transformations proceed through alkylidene dihydropyridine (anhydrobase) intermediates and demonstrate the ability to utilize these species in metal-catalyzed C–C bond forming reactions.

Purpose To present a novel marker-flange, addressing source-reconstruction uncertainties due to the artifacts of a titanium intracavitary applicator used for magnetic resonance imaging (MRI)-guided high-dose-rate (HDR) brachytherapy (BT); and to evaluate 7 different MRI marker agents used for interstitial prostate BT and intracavitary gynecologic HDR BT when treatment plans are guided by MRI. Methods and Materials Seven MRI marker agents were analyzed: saline solution, Conray-60, copper sulfate (CuSO 4 ) (1.5 g/L), liquid vitamin E, fish oil, 1% agarose gel (1 g agarose powder per 100 mL distilled water), and a cobalt–chloride complex contrast (C4) (CoCl 2 /glycine = 4:1). A plastic, ring-shaped marker-flange was designed and tested on both titanium and plastic applicators. Three separate phantoms were designed to test the marker-flange, interstitial catheters for prostate BT, and intracavitary catheters for gynecologic HDR BT. T1- and T2-weighted MRI were analyzed for all markers in each phantom and quantified as percentages compared with a 3% agarose gel background. The geometric accuracy of the MR signal for the marker-flange was measured using an MRI-CT fusion. Results The CuSO 4 and C4 markers on T1-weighted MRI and saline on T2-weighted MRI showed the highest signals. The marker-flange showed hyper-signals of >500% with CuSO 4 and C4 on T1-weighted MRI and of >400% with saline on T2-weighted MRI on titanium applicators. On T1-weighted MRI, the MRI signal inaccuracies of marker-flanges were measured 4 was 0.42 ± 0.14 mm. Conclusion The use of interstitial/intracavitary markers for MRI-guided prostate/gynecologic BT was observed to be feasible, providing accurate source pathway reconstruction. The novel marker-flange can produce extremely intense, accurate signals, demonstrating its feasibility for gynecologic HDR BT.

Polypyridyl ethylenes have been prepared as heterocyclic analogues of tetraphenylethylene. In addition to conventional AIE effects, a derivative possessing a 1,1-bis(2-pyridyl)ethylene fragment displays Zn(2+)-selective enhanced fluorescence in aqueous solution, in contrast to the behavior of isomeric bis(3- and 4-pyridyl)ethylenes. The Zn(2+)-sensing capability of this material is attributed to formation of chelated Zn(2+)-bis(pyridyl) complexes and is supported by the X-ray crystal structure of a bis(2-pyridyl)ethylene-Zn(OAc)2 complex.

4-Alkylpyridines possessing nucleophilic β-dicarbonyl side chains have been converted to spirodihydropyridines upon treatment with ethyl chloroformate and sub-stoichiometric amounts of Ti(O(i)Pr)(4). Alternatively, inclusion of mild base in the reaction medium was found to facilitate generation of anhydrobase intermediates. Subsequent aldol-like condensations with electrophilic side chain moieties followed by hydrolysis delivered benzylically cyclized pyridines in good yield. In situ hydrogenation of cyclized anhydrobase intermediates afforded 4-substituted piperidines.

Two tetraarylethylene derivatives symmetrically functionalized at the 4, 4′, 4″, and 4 ‴ positions with either 4-pyridyl or 3-pyridyl groups were converted to their corresponding tetrapyridinium perchlorate salts upon exposure to Fe(ClO4)3·xH2O. These tetra-perchlorates were isolated as single crystals and their structures were determined by X-ray diffractometry. In both cases extensive hydrogen bonding networks were observed involving pyridinium N–H groups, perchlorate anions, and included water molecules. Additionally, both structures feature hydrophobic crystalline regions formed from stacking of tetraarylethylene cations in helical fashion. Polar pyridinium N–H groups are directed outward from these stacks into hydrophilic crystalline regions containing perchlorate anions and water molecules of hydration. Information obtained regarding the solid state structures of these functionalized tetraarylethylene derivatives should prove useful in design of more elaborate supramolecular architectures.

Two tetrapyridyl-substituted tetraphenylethylenes have been prepared via Suzuki coupling between tetrabromo tetraphenylethylene and 3- or 4-pyridine boronic acid. Both compounds exhibit aggregation-induced emission as determined by solid state fluorescence spectroscopy and solution phase fluorescence measurements performed in aqueous/organic solvent mixtures. Solution phase fluorescence was also found to be switchable as a function of pH. 3-Pyridyl-substituted tetraphenylethylene has been structurally characterized by X-ray crystallography.

Pyridines substituted at the 4-position with alkyl tethers containing beta-dicarbonyl moieties were converted to spirocyclic 4,4-disubstituted dihydropyridines. Optimal conditions for these transformations involved N-acylation of the pyridine substrate with a chloroformate electrophile in the presence of Ti(O(i)Pr)(4). Cyclization products could be easily converted into spiro-piperidine derivatives or elaborated into more complex heterocyclic frameworks via Au-catalyzed cycloisomerization.

Metal-catalyzed transformations have emerged as indispensabletools for carbon-carbon bond formation in contemporary syntheticchemistry. Metal-promoted cross-couplings and metal-catalyzed allylationsrepresent two of the most widely used reaction types. However, cross-couplingreactions involving allylic electrophiles have not been extensivelyexplored. This review presents an overview of efforts aimed at developingmetal-catalyzed allylation reactions between allylic alcohol derivativesand alkenyl or aryl organoboron compounds, leading to 1,4-dienesand allylic arenes, respectively. Particular emphasis is given toregio- and stereoselective allylation procedures. 1 Introduction 2 Allylations Proceeding through π-Allyl Intermediates 2.1 Palladium Catalyzed 2.2 Nickel Catalyzed 2.3 Rhodium Catalyzed 3 Formal S N 2′-Type Allylations 3.1 Palladium Catalyzed 3.2 Rhodium Catalyzed 4 Conclusions and Future Directions

A strain-induced copper-free click reaction mediated by a new and easily prepared cyclooctyne derivative was used to efficiently assemble a DOTA-biotin adduct capable of radionuclide ((68)Ga) uptake. This synthetic strategy offers a potentially general and convenient means of preparing targeted radiolabeling and radiotherapeutic agents.

Solid-state halogen bonding interactions present in four families of structurally similar tritopic haloarenes were examined in an effort to identify molecular features that promote halogen···carbonyl, halogen···halogen, and/or halogen···π interactions. The substrates used in this study all featured three haloarene substituents attached to a central 1,3,5-substituted arene ring with conformationally flexible linkers (ketone or ester groups) in order to systematically vary the polarization of the aryl halogen groups. Within each individual substrate type, however, there was found to be little correlation in the halogen bonding motifs exhibited as a function of halogen present (I, Br, and Cl). In general, the iodoarene derivatives examined exhibited a greater degree of halogen bonding interactions than the bromo and chloro analogues, and a unique bifurcated I···I/I···O═C halogen bonding synthon was identified in two substrates. Halogen bonding contacts observed in tritopic iodoarenes correlated nicely with e...

An experimentally straightforward procedure for the synthesis of structurally elaborate cyclohexadienyl ruthenium(II) complexes has been developed along the lines of the Morita−Baylis−Hillman reaction. Coordination of (cyclopentadienyl)Ru(II) fragments to N-benzyl and N-phenethyl acrylamides was found to facilitate conversion to stable cyclohexadienyl complexes via Bu3P-mediated intramolecular cyclization. An ipso cyclization was observed in all but one case, resulting in formation of five- or six-membered spirolactams at C6 positions of cyclohexadienyl ligands. Acrylamides prepared from dihydroindene and tetrahydronaphthalene precursors were suitable substrates for this transformation, affording access to novel tricyclic cyclohexadienyl complexes. One such complex was characterized by X-ray crystallography.

A ruthenium-mediated dearomatization sequence has been developed that delivers structurally intriguing azaspirolactam products in stereoselective fashion. Treatment of (η6-arene)Ru(cyclopentadienyl) complexes bearing N-benzyl-β-amido phosphonate side chains with excess NaH results in intramolecular nucleophilic aromatic addition to the ipso position of the coordinated arenes. Subsequent Horner–Wadsworth–Emmons (HWE) reaction with added aldehydes affords olefinated spirolactam cyclohexadienyl ruthenium complexes. Mild oxidation with CuCl2 or CuBr2 under CO effects removal and recovery of the CpRu(II) fragment. Substituents present on the cyclohexadienyl skeleton influence the outcome of demetalation and products obtained in this study include functionalized 2-azaspiro[4.5]decanes and tetrahydroisoquinolinones.

A series of four structurally related crownophanes has been prepared and characterized by X-ray crystallography. The crownophanes are based upon a 1,3,5-triaroylbenzene framework and were synthesized via enaminone/alkyne cyclotrimerization. The crownophanes differ in the identity of a peripheral substituent attached to a remote arene ring that is not part of the cyclophane macrocycle. Solid state structural characterization reveals that crownophanes with remote phenyl and phenol substituents self-assemble to form centrosymmetric dimers. Incorporation of remote alkoxy groups (methoxy or ethoxy) disrupts dimerization and leads to catameric networks. Each crownophane crystallized as an inclusion complex or a hydrate and, in one instance, water was found to occupy the macrocyclic cavity.

Monolayers of triaroylbenzene derivatives bearing three octyl groups projecting away from the molecular core and terminated by hydroxyl, carboxylic acid, and methyl ester groups have been studied using surface pressure isotherm measurements and Brewster angle microscopy. The octyl derivative lacking a terminal hydrophilic group forms a monolayer of limited stability. The derivatives with hydrophilic end-groups on the octyl chains form stable monolayers. A reorientation at the water surface under compression from a ‘face-on’ to a distorted ‘edge-on’ arrangement appears likely. At intermediate molecular areas, a phase transition occurs and aggregate formation is observed. Studies of mixtures with methyl stearate exhibit a contrast inversion between the background phase and immiscible domains of methyl stearate supporting the concept of a reorientation of the triaroylbenzene derivatives during compression.

1,2-Dialkylimidazoles are converted to nucleophilic 2-alkylidene imidazoles upon treatment with Boc2O.

Six structures of crystalline materials obtained via the self-assembly of a 1,3,5-triaroylbenzene (TAB) derivative peripherally functionalized with phenol residues (“sticky” groups) have been determined. Two general structural types were observed: highly symmetrical assemblies mediated by direct ArOH···OC hydrogen bonding (space group R3c) and extensively hydrated structures in which water molecules occupy bridging positions between phenol and carbonyl groups (space group P21/n). The former architecture accommodates included solvate molecules (EtOAc or H2O) within an interpenetrated α-Po type TAB network. In the case of the hydrate, water molecules do not appear to be involved in any intermolecular interactions despite excellent hydrogen-bonding ability. Structures of the latter type feature well-defined voids for guest enclathration (guest = acetone, EtOH, MeOH). The observed supramolecular interactions are discussed in the context of potential applications in crystal engineering.

Demetalation of an electron-rich spirolactam-based (cyclohexadienyl)Ru(II) complex is achieved upon treatment with boron trifluoride and a source of chloride ion. The cyclohexadienyl ligand is converted to a cyclohexadienone, cyclohexenone, or cyclohexenone epoxide derivative as a function of the specific reaction conditions. Stable (cyclohexadienyl)ruthenium substrates potentially suitable for demetalation under these conditions are prepared via intramolecular spirocyclization of (η6-arene)Ru precursors; thus, demetalation completes a net Ru-mediated dearomatization sequence. Moreover, the functionalized spirolactam products obtained are structurally distinct from those produced via direct oxidative demetalation.

The title triaroylbenzene derivative forms isostructural lattice inclusion adducts with benzene, toluene, nitrobenzene, and DMSO. The host molecules self-assemble via dimeric C-H...O hydrogen bonds to form 2D tapes with guest molecules occupying interlayer cavities. In contrast, a guest-free form of the inclusion host features a centrosymmetric four-point hydrogen-bonding recognition pattern that results in a square grid packing motif.

An isomeric series of homologous crownophanes (i.e., macrocycles possessing structural features of crown ethers and cyclophanes) has been prepared via a concise and modular synthetic route. Macrocyclization is achieved in reasonable yield during the course of an enaminone-triggered benzannulation with bis(aryl ethynyl ketone) reaction partners. The crownophanes examined were active alkali cation binding agents in the gas phase, but failed to exhibit ionophoric properties in solution. On the basis of X-ray crystallographic analysis, it is concluded that the cyclophane framework of these macrocycles is too large and rigid to allow efficient interaction with the cations examined.

The triaroylbenzene derivative 1,3,5-tris(4-cyanobenzoyl)benzene exhibits the phenomenon of concomitant polymorphism. Two topologically isomeric solid-state networks, hexagonal and ladder, were obtained upon crystallization from acetone/water solution. In contrast, crystallization of the title compound from EtOAc, 3-pentanone, MeNO 2 , DMSO, acetone, and methyl chloroacetate produced isostructural pseudopolymorphic inclusion complexes. In all these six cases, the triaroylbenzene host molecule self-assembles in a 2D lamellar pattern via C-H...O and C-H...N hydrogen bonding with guest solvent molecules residing in interlayer channels. A clathrate of different morphology was obtained upon crystallization from nitroethane. In all seven inclusion adducts, bifurcated C-H...O hydrogen bonding between host donors and the guest acceptors was observed as a common feature. The network topologies in the polymorphic modifications of 1 are different from those observed in the structurally characterized inclusion complexes. Thus, C-H...X (X = N/O) hydrogen bonding appears to significantly influence supramolecular isomerism in this system.