2784 HART AND KIM VOL. 31 diethyl ether was cooled at 0'and a 100% excess of diborane, generated externally from sodium borohydride and boron trifluoride etherate, was bubbled into the solution with a stream of nitrogen. The reaction mixture was allowed to stand at room temperature for 4 hr and most of the ether and excess diborane were removed by distillation under nitrogen. The residue was dissolved in 50 ml of dry chloroform and a 20'% excw of ...