in diethyl ether under N2, 0.9 equiv of i-PrMgCl in Et2O was added slowly over 5 h to stirred soln. of 1 equiv of (Me3Si)2NBCl2 in Et2O at 0°C, warmed toroom temp., stirred overnight; filtered, solvent removed, distd., redistilled; elem. anal.;

in neat (no solvent) byproducts: Me3SiCl; under N2, equimolar amt. of Me3SiNMe2 was added to stirred (Me3Si)2NB(CH(CH3)2)Cl at 0°C, warmed to room temp., stirred overnight; Me3SiCl removed under vac., distd.;