ORGANOBORANES FOR SYNTHESIS. 7. AN IMPROVED GENERAL SYNTHESIS OF PRIMARY AMINES FROM ALKENES via HYDROBORATION-ORGANOBORANE CHEMISTRY

Article abstract of DOI:10.1016/S0040-4020(01)83445-1

Triorganylboranes, R₃B, and diorganylborinicesters, R₂BOR', react readily with preformed chloramine or hydroxylamine-O-sulfonic acid to produce the corresponding primary amines, RNH₂.However, the product of the reaction following hydrolysis is the boronic acid, RB(OH)₂, limiting the yield to 67percent for R₃B and to 50percent for R₂BOR'.This problem has now been overcome with the help of lithium dimethylborohydride, readily converted in situ to dimethylborane.The hydroboration of representative alkenes by dimethylborane provides the corresponding monoorganyldimethylborane, RMe₂B.Treatment of this intermediate with hydroxylamine-O-sulfonic acid provides the desired amines, RNH₂, in isolated yields of 73percent to 95percent.The reaction proceeds with complete retention, reproducing the precise structure of the organic group in the organoboranes, RMe₂B.