Synthesis of β-octabromocalix[4]pyrroles and conformational diversity in their acetone inclusion complexes

Two β-octabromocalix[4]pyrroles were synthesized using a modified strategy, which provides the advantage of large scale preparation with rapid purification. The acetone inclusion complexes of these compounds show different structural orientations featuring diverse types of novel hydrogen bonding owing to varied meso-substitution along with the presence of eight peripheral bromine atoms.     

Oxidative ortho-C-N fusion of aniline by OsO4. Isolation, characterization of oxo-amido Osmium(VI) complexes, and their catalytic activities for oxidative C-C bond cleavage of unsaturated hydrocarbons

In an unusual reaction of osmium(VIII) oxide with p-substituted aromatic amines (X-C(6)H(4)-NH(2), where X = Me, H, Cl) in heptane afforded the brown osmium(VI)-oxo complexes [OsO(L)(2)] (1a-c, L = N-aryl-1,2-arylenediamide) in moderate yields. The ligand L is formed in situ via oxidative ortho-C-N fusion of arylamines. The reaction occurs in an inert atmosphere, and a part of Os(VIII) is used up for the oxidation of aromatic amine. Single crystal X-ray structure of a representative complex 1a is solved. The structural analysis has authenticated the ortho-C-N fusion of ArNH(2) resulting in formation of the diamide ligand, L. The complex as a whole is penta-coordinated, and the coordination sphere has a distorted square pyramidal geometry (tau = 0.26). A similar reaction of osmium(VIII) oxide with the preformed N-phenyl-1,2-phenelene diamine produced the complex 1a in nearly quantitative yield. The substituted phenazine, 5-phenyl-3-phenylimino-3,5-dihydro-phenazine-2-ylamine, is obtained as a byproduct of the latter reaction. The complexes, 1a-c, can be reduced in a reversible one-electron step, as probed by cyclic voltammetry. The one electron reduced paramagnetic Os(V) intermediate is, however, Electron Paramagnetic Resonance (EPR) silent. Solution spectra of the osmium complexes show several multiple transitions in the UV-vis region. Density functional theory calculations were employed to confirm the structural features and to support the spectroscopic assignments. The complex 1a catalyzes oxidation of a wide variety of unsaturated hydrocarbons like alkenes, alkynes, and aldehydes to the corresponding carboxylic acids in the presence of tert-butylhydroperoxide (TBHP) efficiently at room temperature.     

Surface modification of magnetic nanoparticle via Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition

The Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition has been demonstrated to be an effective and orthogonal conjugation reaction to covalently immobilize biomolecules on magnetic nanoparticles (MNPs). The azido group on the MNP surface provides better conjugation efficiency with alkynated molecules. Moreover, the C-terminal alkynated protein was site-specifically immobilized on MNP. The protein binding activity presented by site-specific immobilization is higher than that by random amide bond formation.     

Solution behavior of normal and reverse triblock copolymers (pluronic L44 and 10R5) individually and in binary mixture

Solution properties of pluronics L44 or L [(PEO)(10)(PPO)(23)(PEO)(10)] and 10R5 or R [(PPO)(8)(PEO)(22)(PPO)(8)] were studied individually as well in their binary mixtures in aqueous medium. The critical micelle concentration (CMC), critical micelle temperature, and cloud point (CP) were determined. Ideal and nonideal behaviors of their mixtures in the formation of CMC and CP were observed; the energetics of the studied processes were determined. Spectrophotometry, isothermal titration calorimetry and dynamic light scattering (DLS) methods were used for evaluations. Morphologies of the dispersed L, R, and their mixtures along with their polydispersities were determined from DLS measurements. Atomic force microscopy was also employed. The interfacial properties of L and R were investigated forming Langmuir monolayers in a surface balance. The surface pressures (π) generated by the compounds were moderate, the area per molecule was higher for R than L. R has shown antibacterial activity against both gram positive and gram negative bacteria whereas L was inactive in this respect.     

Effect of rotation in magneto-thermoelastic transversely isotropic hollow cylinder with three-phase-lag model

This article deals with the various heat source responses in a transversely isotropic hollow cylinder under the purview of three-phase-lag (TPL) generalized thermoelasticity theory. In presence of magnetic field and due to the rotating behavior of the cylinder, the governing equations are redefined for generalized thermoelasticity with thermal time delay. In order to obtain the stress, displacement and temperature field, the field functions are expressed in terms of modified Bessel functions in Laplace transformed domain. When the outer radius of hollow cylinder tends to infinity, the corresponding results are discussed. Finally an appropriate Laplace transform inversion technique is adopted.     

Total Synthesis of an Immunomodulatory Phosphoglycolipid from Thermophilic Bacteria

A method for the stereocontrolled synthesis of a bacterial phosphoglycolipid (PGL 1 ) isolated from thermophilic bacteria is described. The key features of the synthesis include a highly α‐selective glycosylation reaction between a trichloroacetimidate donor and a D ‐lyxose‐derived primary alcohol acceptor and the late‐stage incorporation of the phospholipid.     

Bidirectional Chemical Communication between Nanomechanical Switches

The interplay of biological machines depends critically on the bidirectionality of chemical information exchange. The implementation of such a communication procedure for abiological systems is achieved using two nanoswitches that both operate as transmitters and receivers by transfering copper ions in oxidation states +I and +II. Even at micromolar concentrations, communication in both directions is remarkably fast, occurring at t_1/2=2–3 min. Metal ion translocation triggers a 20 Å relocation of the toggle at both nanoswitches, entailing major geometric and electronic changes.     

Rh(III)‐Catalyzed Denitrogenative [4+2] Annulation of Benzamides and 3‐Diazoindolin‐2‐imines: Expedient Access to Indolo[2,3‐c] isoquinolin‐5‐ones

An effective and pragmatic strategy for the synthesis of structurally diverse indolo[2,3‐c]isoquinolin‐5‐ones has been developed via a Rh(III)‐catalyzed C?H activation and [4+2] annulation reaction of N‐methoxybenzamides and 3‐diazoindolin‐2‐imines. The reaction involves the efficient formation of two new (one C?C and one C?N) bonds under operationally simple conditions and has the benefits of a broad substrate scope.     

Three-Component Coupling Synthesis of Diversely Substituted N-Aryl Pyrroles Catalyzed by Iron(III) Chloride

An efficient and operationally simple three-component coupling synthesis of varieties of N-aryl substituted pyrroles is described in the presence of sustainable and environmentally benign metal catalyst, FeCl₃. This method provides a straightforward approach for the synthesis of N-aryl substituted pyrroles in good yields from easily accessible starting materials such as nitroalkenes, 1,3-dicarbonyl compounds, and primary aromatic amines. The reaction proceeds through a catalytic sequence of Fe(III)-catalyzed amination/Michael/cycloisomerization reactions.

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