N,N,N',N',N'',N''-hexamethylphosphoric triamide; ammonium chloride in tetrahydrofuran Ar; addn. of the triflate to a solution of the cuprate at -20 ° C; stirring for 1 h at -20 ° C; addn. of HMPA; stirring for 1 h at 0 ° C; addn. of aqueous NH4Cl in Et2O/petroleum ether; stirring until the organic layer was colorless; filtration; washing of the filtrate with CuSO4, H2O, brine; drying (MgSO4); flash chromy. (1:4 benzene - petroleum ether, silica); distillation (85-95 ° C/0.1 Torr);;

methyllithium in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide the bis-Sn deriv. was treated with 1.2 equiv of MeLi at -98°C, the mixt. was then stirred for 20 min; spectral data (the kind of spectra not indicated) confirm the structure; high-resolution mass spectrometry exhibit satisfactory molecular mass detn.;

in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide treatment of the corresponding (Z)-2,3-bis(trimethylstannyl)-2-alkenoate with MeLi in THF-HMPA (-98°C, 20 min);