in diethyl ether; toluene byproducts: MgBr2; toluene soln. of stannane added to organomagnesium compd. (prepd. in dry ether); heated at the b.p. of toluene (ether distd. off) until a test for bromine was neg. (30 h); cooled; hydrolyzed; org. layer sepd., washed, dried, solvent driven off; recrystd. (propyl alcohol); IR; PMR; elem. anal.;