Boron-Catalyzed Site-Selective Reduction of Carbohydrate Derivatives with Catecholborane

Catalytic sp³ C–O bond cleavage using B­(C₆F₅)₃/HBcat is reported. This method is first demonstrated on simple ethers and silyl protected alcohols, which exhibit reactivity parallel to the known B­(C₆F₅)₃/HSiR₃ system. In more complex carbohydrate derivatives, however, unique selectivities that are not possible with hydrosilane reductants have been achieved, including regioselective cyclizations. Preliminary computational studies suggest that diboryl oxonium ions are disfavored and that four-coordinate boronium ions may contribute to selectivity

Biomimetic Platinum-Promoted Polyene Polycyclizations: Influence of Alkene Substitution and Pre-cyclization Conformations

Results of kinetic experiments and quantum chemical computations on a series of platinum-promoted polycyclization reactions are described. Analyses of these results reveal a reactivity model that reaches beyond the energetics of the cascade itself, incorporating an ensemble of pre-cyclization conformations of the platinum–alkene reactant complex, only a subset of which are productive for bi- (or larger) cyclization and lead to products. Similarities and differences between this scenario, including reaction coordinates for polycyclization, for platinum- and enzyme-promoted polycyclization reactions are highlighted

Is Measured Hearing Aid Benefit Affected by Seeing Baseline Outcome Questionnaire Responses?

PURPOSE: To determine whether hearing aid outcome measured by the Hearing Handicap Inventory (HHI) for the Elderly/Adults (Newman, Weinstein, Jacobson, & Hug, 1990; Ventry & Weinstein, 1982) is differentially affected by informed vs. blind administration of the postfitting questionnaire. METHOD: Participants completed the HHI at their hearing aid evaluation and again at their hearing aid follow-up visit. At follow-up, half received a clean HHI form (blind administration), whereas the remainder responded on their original form (informed administration) and could thus base their follow-up responses on those they gave at the hearing aid evaluation. RESULTS: The data show that for the population examined here, informed administration of the follow-up HHI did not yield a different outcome to blind administration of the follow-up HHI. This was not influenced by past hearing aid use, age of the participant, or the duration of time between baseline questionnaire completion and follow-up completion. CONCLUSION: These data suggest that completion of follow-up questionnaires in either informed or blind format will have little impact on HHI responses, most likely because of the many other factors that combined to influence hearing aid outcome