in tetrahydrofuran (Ar); mixed at -70°C; stirred for 1 h at this temperature; warmed to room temperature; added ice water; dried organic phase (MgSO4); fractionated; elem. anal.;

n-butyllithium byproducts: Sn; (Ar); for 2.5 h at 200°C; dissolution in C6D6; filtration; addn. of n-BuLi; hydrolysis with ice water; drying of organic phase (MgSO4); fractionation;