Palladium‐Catalyzed Annulation of Diarylamines with Olefins through C?H Activation: Direct Access to N‐Arylindoles

A palladium‐catalyzed dehydrogenative coupling between diarylamines and olefins has been discovered for the synthesis of substituted indoles. This intermolecular annulation approach incorporates readily available olefins for the first time and obviates the need of any additional directing group. An ortho palladation, olefin coordination, and β‐migratory insertion sequence has been proposed for the generation of olefinated intermediate, which is found to produce the expected indole moiety.     

An efficient one-pot synthesis of C2-symmetric triazolophanes by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction

A facile and efficient one-pot synthesis of 12-15-membered triazolophanes has been accomplished using CuAAC methodology. The formation of triazolophanes was confirmed by spectral analysis and the products were isolated in good yield. The effect of solvents on this reaction was also studied.     

Internal Spin Trapping of Thiyl Radical during the Complexation and Reduction of Cobalamin with Glutathione and Dithiothrietol

The activation of cobalamin requires the reduction of Cbl(III) to Cbl(II). The reduction by glutathione and dithiothreitol was followed using visible spectroscopy and electron paramagnetic resonance. In addition the oxidation of glutathione was monitored. Glutathione first reacts with oxidized Cbl(III). The binding of a second glutathione required for the reduction to Cbl(II) is presumably located in the dimethyl benzimidazole ribonucleotide ligand cavity. The reduction of Cbl(III) by dithiothreitol, which contains two thiols, is much faster even though no stable Cbl(III) complex is formed. The reduction, by both thiol reagents, results in the formation of thiyl radicals, some of which are released to form oxidized thiol products and some of which remain associated with the reduced cobalamin. In the reduced state the intrinsic lower affinity for the benzimidazole base, coupled with a trans effect from the initial GSH bound to the β-axial site and a possible lowering of the pH results in an equilibrium between base-on and base-off complexes. The dissociation of the base facilitates a closer approach of the thiyl radical to the Co(II) α-axial site resulting in a complex with ferromagnetic exchange coupling between the metal ion and the thiyl radical. This is a unique example of 'internal spin trapping' of a thiyl radical formed during reduction. The finding that the reduction involves a peripheral site and that thiyl radicals produced during the reduction remain associated with the reduced cobalamin provide important new insights into our understanding of the formation and function of cobalamin enzymes.     

Synthesis and mesomorphic properties of 4-alkylamino-4'-substituted diphenyldiacetylenes

Various substituted aminodiphenyldiacetylenes of the type with X = C₃H₇, C₅H₁₁, F or NO₂ and R, R' = H, CH₃-C₆H₁₃ were synthesized and their mesomorphic properties determined. Semi-empirical and ab initio quantum chemical calculations using AM1, 421G and 631G* suggested that the amino group would increase the dielectric anisotropy and optical birefringence as compared to the alkyl chain. Mesomorphic properties were found to be poor with the maximum nematic phase range being 44.8°C and many of the compounds having no nematic phase. Both melting temperatures and enthalpies for those having nematic phases were too high to form good eutectic mixtures.     

Asymmetric synthesis of a dopamine D1 agonist,dihydrexidine from d-serine

A scalable asymmetric synthesis of trans-2-amino-6,7-dimethoxy-1-phenyltetralin 2 and its N-nosyl derivative 12 have been achieved from Garner aldehyde derived from easily available d-serine using a stereoselective PhMgBr addition, Wittig reaction and TFA-mediated Friedel–Crafts cyclization as the key steps. The synthesis of dihydrexidine is accomplished from the N-nosyl-2-amino-1-phenyltetralin 12.     

A Convenient Synthesis of 4-(2-Furyl)-2-substituted Thiazoles Utilising [Hydroxy(tosyloxy)iodo]benzene

A facile synthesis of 4-(2-furyl)-2-substituted thiazoles by hypervalent iodine oxidation of 2-acetylfuran (1) using [hydroxy(tosy-loxy)iodo]benzene, followed by treatment of the reaction mixture with appropriate thioureas/thioamides is described.     

First total synthesis of parvistone C and its C8-epimer

Diastereoselective first total synthesis of parvistone C 1 and C8-epimer 1a are described. The key features of our synthesis include Sharpless asymmetric dihydroxylation, stereoselective aryl Grignard reactions, Still–Gennari olefination, and intramolecular cyclization.     

Light-mediated and H-bond facilitated liposomal release: the role of lipid head groups in release efficiency

Syntheses of coumarin-containing lipids and liposomal formulations incorporating these lipids are studied. The influence of the lipid head groups in enhancing the release efficiency of these liposomes under light irradiation is studied and a molecular mechanism is provided.     

Effect of spherical aberrations in tight focusing of higher order radially polarized beam

The effect of spherical aberration, in higher order radially polarized beam, is investigated theoretically by vector diffraction theory. It is observed that an increase in aberration results in the spreading of the intensity distribution, positional shift and the size of the generated focal pattern.