Ligand-free nickel catalyzed perfluoroalkylation of arenes and heteroarenes

We describe a “ligand-free” Ni-catalyzed perfluoroalkylation of heteroarenes to produce a diverse array of trfiluoromethyl, pentafluoroethyl and heptafluoropropyl adducts. Catalysis proceeds at room temperature via a radical pathway. The catalytic protocol is distinguished by its simplicity, and its wide scope demonstrates the potential in the late-stage functionalization of drug analogues and peptides.

A ligand-free, room temperature, Ni-catalyzed perfluoroalkylation of heteroarenes produced a diverse array of polyfluorinated adducts; potential in the late-stage functionalization of drugs and peptides is also demonstrated.     

Understanding the structural properties of a dendrimeric material directly from powder X-ray diffraction data

Complete structure determination of an early-generation dendrimeric material has been carried out directly from powder X-ray diffraction data, using the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement. This work represents the first application of modern direct-space techniques for structure determination from powder X-ray diffraction data in the case of a dendrimeric material and paves the way for the future application of this approach to enable complete structure determination of other dendrimeric materials that cannot be prepared as single crystal samples suitable for single crystal X-ray diffraction studies.     

Speciation of M+3-hydroxypyrone chelation complexes by electrospray ionization ion trap and Fourier transform ion cyclotron resonance mass spectrometry

Kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone) is known to have a high affinity for transition metals, and it and its derivatized cogeners are used both analytically and clinically. The interactions between kojic acid (KA) and eleven +3 metals (Al(+3), As(+3), Cr(+3), Ga(+3), Fe(+3), In(+3), Yb(+3), Y(+3), Gd(+3), Nd(+3), La(+3)) were examined by electrospray ionization mass spectrometry (ESI-MS) using an ion trap in an aqueous medium. For a subset of five ions, Fourier transform ion cyclotron resonance (FTICR)-MS was conducted to provide accurate mass confirmation of peak assignments for metals having clustering of abundant isotopes. KA readily formed complexes with all the metal ions tested. The most common complexes observed were ML(3)H(+) and M(2)L(5). Different behavior was seen for small and large ionic radius ions, with a relative cut-off between In(+3) ( approximately 80 pm) and Yb(+3) ( approximately 87 pm); a striking trend in % collision energy vs. cluster complexity was revealed. The KA-Cr(+3)complex shows a high affinity for H(2)O molecules in the gas phase, whilst In(+3) shows a preference for dimetal complexes and Y(+3) a deviant behavior when complexed to two neutrals.     

Algebraic structure of fermion density matrices. II

The properties of the algebraic structure of fermion density matrices are studied. The algebraic structure of a density matrix leads to a more varied and detailed classification scheme than that offered by the usual shell structure approach. Investigation of the algebraic structure of fermion density matrices by the methods of algebraic topology leads to a classification scheme based on Betti numbers.     

Scope of direct arylation of fluorinated aromatics with aryl sulfonates

The scope and limitations of direct arylation of fluorinated aromatics with aryl sulfonates was examined. Pd(OAc)(2), in the presence of MePhos and KOAc in THF, efficiently catalyzed the direct arylation of fluoro aromatics with aryl triflates under ambient conditions. Sterically hindered triflates and heteroaryl triflates gave good to excellent yields of the cross coupled products using a modified catalyst system which involves Pd(OAc)(2)-RuPhos at 100 °C. The direct arylation of electron deficient arenes with aryl mesylates is also established using Pd(OAc)(2)-SPhos as the catalyst in toluene-(t)BuOH at 120 °C.     

Effects of structure on properties of some new aromatic-aliphatic polybenzimidazoles

Polybenzimidazoles were prepared in poly(phosphoric acid) from isophthalic, m- and p-phenylene diacetic, succinic, adipic, suberic, and sebacic acids and 3,3′-diaminobenzidine, 3,3′,4,4′-tetraaminodiphenyl ether and 3,3′,4,4′-tetraaminodiphenylmethane. The thermal, mechanical, and bonding properties were studied. A 3:1 copolymer of isophthalic and m-phenylenediacetic acid with 3,3′-diaminobenzidine showed the best results as far as isothermal oxidation resistance and thermal and processing characteristics.     

The relation between collinear and 3-D dynamical calculations of reactive molecular collisions

One important difference between the results of collinear and of full 3-D dynamical computations arises from the difference in the available volume in phase space (1-D versus 3-D) which can be termed a “dimensionality-bias”. Correction for this phase space factor allows for a more realistic estimate of reaction cross sections, branching ratios and 3-D product energy distributions from collinear calculations.     

Electron-impact induced hydrogen scrambling in cyclohexanol and methylcyclohexanols

Exact mass measurements and the mass spectral behavior of O-deuterated cyclohexanols, coupled with a re-evaluation of previously published data^1,2, show that the hydrogen attached to oxygen undergoes partial scrambling with the 2, 3, 5 and 6 position ring hydrogens prior to or during the formation of the major primary fragment ions.