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