in diethyl ether to a stirred soln. of the ester (in dry ether) is added bromotrimethylsilane (in dry ether) dropwise; ether is removed at residual pressure of 7 Torr , fractionation;

in diethyl ether to a soln. of (CH3)3GeC((C4H9)3Sn)HCOOCH3 in dry ether is added with stirring (CH3)3GeBr; the reaction mixture is stirred for 96 h at room temp.; fractionation; elem. anal.;

in pentane to a soln. of (CH3)3GeCH((C4H9)3Sn)COOCH3 in dry pentane is added with stirring and cooling (-30°C) a soln. of BrB(N(CH3)2 dropwise under Ar; evapn. (only Z-isomer is detected by IR and NMR), fractionation yields mixt. of isomers, residue is bromotributyl stannane;