Sensitivity studies of the swift radionuclide transport model

There are large uncertainties in the input waste depository. The aim of the sensitivity studies was to identify these uncertainties and to reduce the number of SWIFT transport calculations. The sensitivity analysis was applied to a hypothetical problem consisting of both a reference site containing a nuclear waste depository and a disruptive-event scenario for the possible release of radioactive materials to the biosphere. Results are presented for the total radionuclide discharge to a river in the 10/sup 6/-year time period following depository closure. (DLC

Synthesis of homoallylic amines by hydrozirconation-imine addition of allenes

(Chemical Equation Presented) Hydrozirconation of allenes followed by in situ transmetalation to dialkylzinc leads to the formation of an allylic zinc species that, upon addition of aldimines to the reaction mixture, provides homoallylic amines in 64-85% yield. © 2005 American Chemical Society

Catalytic C–H bond silylation of aromatic heterocycles

This protocol describes a method for the direct silylation of the carbon–hydrogen (C–H) bond of aromatic heterocycles using inexpensive and abundant potassium tert-butoxide (KOt-Bu) as the catalyst. This catalytic cross-dehydrogenative coupling of simple hydrosilanes and various electron-rich aromatic heterocycles enables the synthesis of valuable silylated heteroarenes. The products thus obtained can be used as versatile intermediates, which facilitate the divergent synthesis of pharmaceutically relevant compound libraries from a single Si-containing building block. Moreover, a variety of complex Si-containing motifs, such as those produced by this protocol, are being actively investigated as next-generation therapeutic agents, because they can have improved pharmacokinetic properties compared with the original all-carbon drug molecules. Current competing methods for C–H bond silylation tend to be incompatible with functionalities, such as Lewis-basic heterocycles, that are often found in pharmaceutical substances; this leaves de novo synthesis as the principal strategy for preparation of the target sila-drug analog. Moreover, competing methods tend to be limited in the scope of hydrosilane that can be used, which restricts the breadth of silicon-containing small molecules that can be accessed. The approach outlined in this protocol enables the chemoselective and regioselective late-stage silylation of small heterocycles, including drugs and drug derivatives, with a broad array of hydrosilanes in the absence of precious metal catalysts, stoichiometric reagents, sacrificial hydrogen acceptors or high temperatures. Moreover, H_2 is the only by-product generated. The procedure normally requires 48–75 h to be completed