in dichloromethane N2 atmosphere, addn. of soln. of Me2BBr to soln. of Sn compd. (-78 to -60°C, 2 h), warming to room temp., stirring (room temp., 1 h), addn. of Me2SnCl2 soln. (room temp., 45 min), redn. of volume, addn. to soln. of tBuBBr2 (-78°C, 90 min); warming to room temp., stirring (room temp., 4 d), removement of volatiles (25°C, 12 Torr/1E-3 Torr), pptn. (Me2SnBr2, petroleum ether, -30°C), filtration, removement of volatiles (0°C, 12 Torr/1E-3 Torr), distn.; elem. anal;

in dichloromethane N2 atmosphere, addn. of soln. of stannyl compound to soln. of borane at -55 to -50°C (1.5 h) with stirring, slow warming to room temp., stirring (25°C, 12 h); removement of solvent (25°C, 12 Torr), pptn. of Me2SnBr2 (petroleum ether, -30°C, 4-6 h), filtration, evapn. of solvent (25°C, 12 Torr), condensation into a cooled trap (-78°C) at 25-28°C (1E-6 Torr); elem. anal.;

in dichloromethane N2 atmosphere; dissolution (CH2Cl2), addn. of tBuBBr2 (-70°C), thawing, stirring (12 h); removal of CH2Cl2 (12 Torr), dissolution (petroleum ether), cooling (12 h, -30°C), filtration, removal of solvent (12 Torr); elem. anal.;

in toluene N2 atmosphere, addn. of soln. of borane to soln. of stannyl compound at -60 to -50°C with stirring, warming to room temp., reflux (36 h); NMR-monitoring, spectroscopic yield 50percent;

in toluene N2 atmosphere, addn. of soln. of borane to soln. of stannyl compound at -60 to -50°C with stirring, warming to room temp., reflux (36 h),addn. of H2O, reflux (72 h); removement of solvent (vacuum), sublimation (43-45°C, 1E-6 Torr);elem. anal.;