Practical Synthesis of Unsymmetrical Tetraarylethylenes and Their Application for the Preparation of [Triphenylethylene−Spacer−Triphenylethylene] Triads

We have demonstrated that reactions of diphenylmethyllithium with a variety of substituted benzophenones produces corresponding tertiary alcohols that are easily dehydrated, without any need for purification, to produce various unsymmetrical and symmetrical tetraarylethylenes in excellent yields. The simplicity of the method allows for the preparation of a variety of ethylenic derivatives in multigram (10−50 g) quantities with great ease. The methodology was successfully employed for the preparation of various triphenylethylene (TPE)-based triads (i.e., TPE−spacer−TPE) containing polyphenylene and fluoranyl-based spacers. The ready availability of various substituted tetraarylethylenes allowed us to shed light on the effect of substituents on the oxidation potentials (Eox) of various tetraarylethylenes. Moreover, the electronic coupling among the triphenylethylene moieties in various TPE−spacer−TPE triads was briefly probed by electrochemical and optical methods

A convenient tandem one-pot synthesis of donor-acceptor-type triphenylene 2,3-dicarboxylic esters from diarylacetylene

A tandem one-pot method for the direct synthesis of polysubstituted triphenylene 2,3-dicarboxylic esters with different substitution patterns was developed by enyne metathesis of diarylacetylene, followed by Diels–Alder, aromatization and a cyclization cascade

Rosamines Targeting the Cancer Oxidative Phosphorylation Pathway

Reprogramming of energy metabolism is pivotal to cancer, so mitochondria are potential targets for anticancer therapy. A prior study has demonstrated the anti-proliferative activity of a new class of mitochondria-targeting rosamines. This present study describes in vitro cytotoxicity of second-generation rosamine analogs, their mode of action, and their in vivo efficacies in a tumor allografted mouse model. Here, we showed that these compounds exhibited potent cytotoxicity (average IC50<0.5 µM), inhibited Complex II and ATP synthase activities of the mitochondrial oxidative phosphorylation pathway and induced loss of mitochondrial transmembrane potential. A NCI-60 cell lines screen further indicated that rosamine analogs 4 and 5 exhibited potent antiproliferative effects with Log10GI50 = -7 (GI50 = 0.1 µM) and were more effective against a colorectal cancer sub-panel than other cell lines. Preliminary in vivo studies on 4T1 murine breast cancer-bearing female BALB/c mice indicated that treatment with analog 5 in a single dosing of 5 mg/kg or a schedule dosing of 3 mg/kg once every 2 days for 6 times (q2d×6) exhibited only minimal induction of tumor growth delay. Our results suggest that rosamine analogs may be further developed as mitochondrial targeting agents. Without a doubt proper strategies need to be devised to enhance tumor uptake of rosamines, i.e. by integration to carrier molecules for better therapeutic outcome

Triarylmethyl Cation-Catalyzed Three-Component Coupling for the Synthesis of Unsymmetrical Bisindolylmethanes [post-print]

An efficient synthesis of unsymmetrical bisindolylmethanes has been accomplished using triarylmethyl cations to catalyze the reaction of N-arylimines with two different indoles. Optimization of the organocatalyst by tuning cation stability allows for excellent single addition selectivity when coupled with p-nitrophenyl imines. The optimal catalyst is commercially available, and the reaction minimizes waste and environmental impact by employing a one-to-one ratio of starting materials. The intermediates can be isolated or used in situ in a one-pot two-step reaction to generate unsymmetrical bisindolylmethanes in high yields. The reaction tolerates a broad range of imines with the highest yields observed for electron-poor and neutral imines. A wide range of indole nucleophiles are also successfully employed allowing for the creation of a large variety of unsymmetrical bisindolylmethanes

Synthesis and inclusion studies of stable allicin mimics as novel antimicrobial agents

Includes abstract.Includes bibliographical references (p. 193-202).Allicin, a known constituent of garlic, is a potent but unstable antimicrobial agent. Consideration of the underlying features responsible for allicin’s activity, as well as its instability, prompted an investigation into substituted S-aryl alkylthiosulfinates as a class of potential allicin mimics with enhanced stability. Synthesis of the targets also inspired development of a novel unsymmetrical disulfide synthesis. This thesis describes the development of a new methodology for synthesizing unsymmetrical disulfides. The synthesis involves converting a thiol to a sulfenylating agent by 1-chlorobenzotriazole (BtCl) in the presence of 1,2,3-benzotriazole (BtH). Addition of a second thiol affords unsymmetrical disulfides in excellent yields. In addition to being a one-pot methodology, the approach offers attractive environmentally friendly and cost-saving aspects. The methodology proved to be versatile, producing all types of unsymmetrical disulfides; aromatic-aliphatic disulfides, aromatic-aromatic disulfides as well as aliphatic-aliphatic disulfides including unsymmetrical cysteine disulfides

Ba2AlSi5N9

Ba2AlSi5N9 was synthesized starting from Si3N4, AlN, and Ba in a radio-frequency furnace at temperatures of about 1725°C. The new nitridoalumosilicate crystallizes in the triclinic space group P1 (no. 1), a=9.860(1) Å, b=10.320(1) Å, c=10.346(1) Å, α=90.37(2)°, β=118.43(2)°; γ=103.69(2)°, Z=4, R1=0.0314. All synthesized crystals were characteristically twinned by reticular pseudomerohedry with twin law (1 0 0, −0.5 −1 0, −1 0 −1). The crystal structure of Ba2AlSi5N9 was determined from single-crystal X-ray diffraction data of a twinned crystal and confirmed by Rietveld refinement both on X-ray and on neutron powder diffraction data. Statistical distribution Si/Al is corroborated by lattice energy calculations (MAPLE). 29Si and 27Al solid-state NMR are in accordance with the crystallographic results. Ba2AlSi5N9 represents a new type of network structure made up of TN4 tetrahedra (T = Si, Al). Highly condensed layers of dreier rings with nitrogen connecting three neighboring tetrahedral centers occur which are further crosslinked by dreier rings and vierer rings. The dreier rings consist of corner-sharing tetrahedra, whereas some of the vierer rings exhibit two pairs of edge-sharing tetrahedra. In the resulting voids of the network there are eight different Ba2+ sites with coordination numbers between 6 and 10. Thermogravimetric investigations confirmed a thermal stability of Ba2AlSi5N9 up to about 1515°C (He atmosphere). Luminescence measurements on Ba2AlSi5N9:Eu2+ (2 mol % Eu2+) with an excitation wavelength of 450 nm revealed a broadband emission peaking at 584 nm (FWHM=100 nm) originating from dipole-allowed 4f6(7F)5d1 → 4f7(8S7/2) transitions

“Separated” versus “Contact” Ion-Pair Structures in Solution from Their Crystalline States: Dynamic Effects on Dinitrobenzenide as a Mixed-Valence Anion

Qualitative structural concepts about dynamic ion pairs, historically deduced in solution as labile solvent-separated and contact species, are now quantified by the low-temperature isolation of crystalline (reactive) salts suitable for direct X-ray analysis. Thus, dinitrobenzenide anion (DNB-) can be prepared in the two basic ion-paired forms by potassium-mirror reduction of p-dinitrobenzene in the presence of macrocyclic polyether ligands:  LC (cryptand) and LE (crown-ethers). The crystalline “separated” ion-pair salt isolated as K(LC)+//DNB- is crystallographically differentiated from the “contact” ion-pair salt isolated as K(LE)+DNB- by their distinctive interionic separations. Spectral analysis reveals pronounced near-IR absorptions arising from intervalence transitions that characterize dinitrobenzenide to be a prototypical mixed-valence anion. Most importantly, the unique patterns of vibronic (fine-structure) progressions that also distinguish the “separated” from the “contact” ion pair in the crystalline solid state are the same as those dissolved into THF solvent and ensure that the same X-ray structures persist in solution. Moreover, these distinctive NIR patterns are assigned with the aid of Marcus−Hush (two-state) theory to the “separated” ion pair in which the unpaired electron is equally delocalized between both NO2-centers in the symmetric ground state of dinitrobenzenide, and by contrast, the asymmetric electron distribution inherent to “contact” ion pairs favors only that single NO2-center intimately paired to the counterion. The labilities of these dynamic ion pairs in solution are thoroughly elucidated by temperature-dependent ESR spectral changes that provide intimate details of facile isomerizations, ionic separations, and counterion-mediated exchanges

The relationship of molecular structure to mesomorphism in some aromatic esters of diphenols

Matter exists principally in three distinct states -crystalline solid, isotropic liquid, and gas. Individual units in both the liquid and gaseous state are more or less mobile, while in the crystalline solid state these units are held in the rigid, three dimensional configuration of a crystalline lattice. Consequently, the crystalline solid is regarded as the most highly ordered of the three states of matter. Heating a crystalline solid increases the thermal vibrations and the ordered arrangement begins to break down. The solid passes from the highly organized crystalline state to the disorganized isotropic liquid. In 1888, Friedrich Reinitzer discovered that, on melting cholesteryl benzoate, the solid collapsed to form a turbid liquid which, on further heating, gave the normal, transparent, isotropic liquid.1 This turbid liquid exhibited properties of both liquid and crystalline forms of matter; the substance was both birefringent (a property of crystals) and fluid. Although Reinitzer is credited with discovering the liquid crystalline phenomenon, Lehmann2 was first to suggest the name "liquid crystals", and to describe their properties. Later, Friedel3,4 proposed the term "mesomorphs" or "mesophases" for substances that were neither isotropic liquids nor crystalline solids. Since both terminologies are generally accepted, the terms liquid crystal and mesomorph, or liquid crystallinity and mesomorphism, will be used interchangeably throughout this thesis