Substituent effects on the stability and reactivity of norbornenyl and nortricyclyl radicals

The products of addition of thioacetic acid to norbornadiene, and of tributyltin hydride and triphenyltin hydride reduction of exo-2-bromo-anti-7-thioacetoxynorborn-5-ene (7), and trans-5-bromo-3-thioacetoxynortricyclene (8), have been examined. In contrast to results obtained with the corresponding acetoxy compounds, the product ratios vary with the reducing reagent and the starting material and the ratio of (rate of rearrangement)/(rate of hydrogen atom abstraction) is significantly less for the thioacetoxy substituted radicals.