74 research outputs found
Racial/ethnic differences in clinical trial enrollment, refusal rates, ineligibility, and reasons for decline among patients at sites in the National Cancer Institute's Community Cancer Centers Program
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106705/1/cncr28483.pd
Towards novel difluorinated sugar mimetrics; syntheses and conformational analyses of highly-functionalised difluorinated cyclooctenones
Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT 19F NMR. Topological characterisation by molecular modelling and NOESY/ROESY experiments offered a number of challenges, but allowed the identification of two favoured boat-chair conformers which interconverted by pseudorotation with relatively large activation barriers
Thermochemical investigation of phosphine ligand substitution reactions involving trans-(PR3)2Cl2Ru=CH-CH=CPh2 complexes
The enthalpies of reaction of (PPh3)(2)Cl2Ru=CH-CH=CPh2 (1) with a series of tertiary phosphine ligands, leading to the formation of (PR3)(2)Cl2Ru=CH-CH=CPh2 complexes (PR3 = (PPr3)-Pr-i, PBz(3), PPh2Cy, PPhCy2, PCy3, and (PBu3)-Bu-i) have been measured, by solution calorimetry in CH2Cl2 at 30 degrees C. The range of reaction enthalpies spans some 6.5 kcal/mol and helps to establish a relative order of complex stability for,these six ruthenium carbene complexes. The enthalpies of reaction for tertiary phosphine complexes, trans-(PR3)(2)Cl2Ru=CH-CH=CPh2, are as follows (PR3, kcal/mol): PPh3, 0; PBz(3), -1.3 (0.2); PCyPh2, -1.8 (0.2); PCy2Ph, -3.8 (0.2); (PBu3)-Bu-i, -3.8 (0.2); (PPr3)-Pr-i, -5.2 (0.1); PCy3, -6.5 (0.3). The thermodynamics of the exchange of these sterically demanding tertiary phosphine-ligands for PPh3 in 1 provides a measurement of the relative importance of phosphine steric and electronic properties/character to the enthalpy of reaction in this system. Correlations of various factors gauging the electron-donating properties of the phosphine ligands clearly show the electronic factor to be the overwhelming contributor to the enthalpy of reaction in this system
Synthesis and characterization of novel polyimides with 2,2-bis[4(4-aminophenoxy)phenyl]phthalein-3?,5?-bis(trifluoromethyl)anilide
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