Rapid synthesis of diversely functionalized 3,4,7-trisubstituted indoles

Synthetic approaches are described for the synthesis of 4-alkoxyindole-7-carboxamides and 4-alkoxy-3-cyanoindole-7-carboxamides, which are useful intermediates in medicinal chemistry research. Two strategies were employed, highlighted by a Bartoli indole synthesis or a sequential and regioselective use of chlorosulfonyl isocyanate to install both the 3-cyano and 7-carboxamido groups. These routes are scalable and afford diversely functionalized indoles for further elaboration.     

High sensitive measurements of absorption coefficient and optical nonlinearities

Accurate knowledge of absorption coefficient of a sample is a prerequisite for measuring the third-order optical nonlinearity of materials, which can be a serious limitation for unknown samples. We introduce a method, which measures both the absorption coefficient and the third-order optical nonlinearity of materials with high sensitivity in a single experimental arrangement. We use a dual-beam pump-probe experiment and conventional single-beam z-scan under different conditions to achieve this goal with communication relevant wavelength. We also demonstrate a counterintuitive coupling of the non-interacting probe-beam with the pump-beam in pump-probe z-scan experiment.     

Universality in the length spectrum of integrable systems

The length spectrum of periodic orbits in integrable hamiltonian systems can be expressed in terms of the set of winding numbers {M ₁,…,M _f} on thef-tori. Using the Poisson summation formula, one can thus express the density, Σδ(T−T _M), as a sum of a smooth average part and fluctuations about it. Working with homogeneous separable potentials, we explicitly show that the fluctuations are due to quantal energies. Further, their statistical properties are universal and typical of a Poisson process as in the corresponding quantal energy eigenvalues. It is interesting to note however that even though long periodic orbits in chaotic billiards have similar statistical properties, the form of the fluctuations are indeed very different.     

A general synthetic route to 4-substituted-2,2′-bithiophenes

A new synthetic route to 4-substituted-2,2′-bithiophenes has been developed utilizing 4-bromo-2,2′-bithiophene ( 1 ). Formation of the bithienyllithium adduct via halogen-metal exchange was found to be problematic and resulted in complex mixtures of products. The Grignard reagent of 1 can be obtained easily via the “entrainment” method, allowing the production of 4-substituted-2,2′-bithiophenes (where sub-stituent = octyl, hydroxyethyl, hydroxymethyl, carboxy, carbomethoxy, acetoxyethyl, and acetoxymethyl).     

Palladium(II)‐Catalyzed meta‐CH Olefination: Constructing Multisubstituted Arenes through Homo‐Diolefination and Sequential Hetero‐Diolefination

Divinylbenzene derivatives represent an important class of molecular building blocks in organic chemistry and materials science. Reported herein is the palladium‐catalyzed synthesis of divinylbenzenes by meta‐C? H olefination of sulfone‐based arenes. Successful sequential olefinations in a position‐selective manner provided a novel route for the synthesis of hetero‐dialkenylated products, which are difficult to access using conventional methods. Additionally, 1,3,5‐trialkenylated compounds can be generated upon successful removal of the directing group.     

Contrasting Response of Two Dipolar Fluorescence Probes in a Leucine‐Based Organogel and Its Implications

The microenvironments of a leucine‐based organogel are probed by monitoring the fluorescence behavior of coumarin 153 (C153) and 4‐aminophthalimide (AP). The steady‐state data reveals distinctly different locations of the two molecules in the gel. Whereas AP resides close to the hydroxyl moieties of the gelator and engages in hydrogen‐bonding interactions, C153 is found in bulk‐toluene‐like regions. In contrast to C153, AP exhibits excitation‐wavelength‐dependent emission, indicating that the environments of the hydrogen‐bonded AP molecules are not all identical. A two‐component fluorescence decay of AP in gel, unlike C153, supports this model. A time‐resolved fluorescence anisotropy study of the rotational motion of the molecules also reveals the strong association of only AP with the gelator. That AP influences the critical gelation concentration implies its direct involvement in the gel‐formation process. The results highlight the importance of guest–gelator interactions in gels containing guest molecules.     

Interaction of RuIII(EDTA) with cellular thiols and O2: biological implications thereof

Reaction of [Ru^III(EDTA)(CyS)]^2? (edta^4? = ethylenediaminetetraacetate; CySH = cysteine) with molecular oxygen (O₂) has been studied as a function of pH (4.0–8.0) and cysteine concentration (0.2–2.0 mM) at room temperature (25 °C). Biological activities of the [Ru(EDTA)]/CySH/O₂ system pertaining to cleavage of supercoiled plasmid DNA to its nicked open circular form has been explored in this work. Results are discussed in regard to the reaction of the ruthenium(III)-complex with molecular oxygen) and a working mechanism is proposed for the biological activities of the ruthenium(III)-complex in the presence of O₂.     

Synthesis of 8‐Aminoquinolines by Using Carbamate Reagents: Facile Installation and Deprotection of Practical Amidating Groups

Described herein is the development of practical routes to 8‐aminoquinolines by using readily installable and easily deprotectable amidating reagents. Two scalable procedures were optimized under Rh^III‐catalyzed conditions: i) the use of pre‐generated chlorocarbamates and ii) a two‐step one‐pot process that directly employs carbamates. Both approaches are highly convenient for the gram‐scale synthesis of 8‐aminoquinolines under mild conditions. Facile deprotection of the synthetically versatile amidating groups was achieved under the Pd‐catalyzed transfer hydrogenation conditions with simultaneous deoxygenation of quinoline N‐oxides, thus yielding 8‐aminoquinolines in excellent overall efficiency.     

Synthesis Characterization and Viscosity Studies of Homopolymer of Methyl Methacrylate and Copolymer of Methyl Methacrylate and Styrene

A homopolymer of methyl methacrylate (MMA) and its copolymer with styrene at different compositions were synthesized and characterized. Viscosity measurements of the synthesized homopolymer and the copolymers in toluene solutions were performed at 313 K. Different equations were used to calculate the intrinsic viscosity, viscometric constants values, and molecular weight of the synthesized polymers. The values of intrinsic viscosity and viscosity average molecular weight obtained by the two methods (single point determination and graphical extrapolation) were compared in order to verify the validity of the single point determination for the polymers. Viscometric properties derived included the specific viscosity (it determines the contribution of the solute to the viscosity of the solution), the reduced viscosity (that provides a measure of the polymer capacity for increasing the solution viscosity), and the intrinsic viscosity.     

11-Step enantioselective synthesis of (-)-lomaiviticin aglycon

Lomaiviticins A and B are complex antitumor antibiotics that were isolated from a strain of Micromonospora. A confluence of several unusual structural features renders the lomaiviticins exceedingly challenging targets for chemical synthesis. We report an 11-step, enantioselective synthetic route to lomaiviticin aglycon. Our route proceeds by late-stage, stereoselective dimerization of two equivalent monomeric intermediates, a transformation that may share parallels with the natural products' biosyntheses. The route we describe is scalable and convergent, and it lays the foundation for determination of the mode of action of these natural products.