in chloroform-d1 BF3 and BCl3 passed through soln. of amine in dry CDCl3 at -50°C, excess of amine added or equilibrated mixt. of BF3 and BCl3 added to soln. of amine in dry CDCl3, frozen, degassed in vac.; without isolation;

in chloroform-d1 excess of BBr3 dissolved in dry CDCl3 under N2, added to amine-BF3 soln., excess of amine added or equilibrated mixt. of BF3 and BBr3 added to soln. of amine in dry CDCl3, frozen, degassed in vac.; without isolation;