Selective reductions. Part 60: Chemoselective reduction of organyl azides with dichloroborane–dimethyl sulfide

The rate and stoichiometry of the reduction of an organyl azide with BH3·THF was examined under standardized conditions at room temperature. Borane derivatives, such as dialkyl-, alkoxy-, and haloboranes were also examined for the reduction of azides. This study revealed BHCl2·SMe2 to be the most suitable reagent for the reduction of azides. The chemoselectivity of this reagent was also studied by reducing n-hexyl azide in the presence of representative series of functional groups, including esters, halides, nitriles, and nitro groups. BHCl2·SMe2 reduces azides in the presence of all of the above functional groups as well as olefins. Taking advantage of the differences in reactivity of BHCl2·SMe2 and BH3·THF or BH3·SMe2, it is now possible to reduce selectively an azide in the presence of olefins or to hydroborate an olefin in the presence of azides by a judicious choice of the reagent.