Catalytic Dearomatization of N-Heteroarenes with Silicon and Boron Compounds.

Dearomatized N-heterocycles are an important class of structural motifs for organic synthesis and chemical biology. The catalytic dearomative reduction of unactivated N-heteroarenes using silicon and/or boron-containing compounds as a reductant is one of the most straightforward alternatives to hydrogenation. However, thus far, there are few reported examples on the catalytic reduction of N-heteroaromatic compounds with silane or borane reducing agents. This Review presents recent advances in the catalytic reduction of unactivated N-heteroarenes by hydrosilanes, hydroboranes, silaboranes, and diboranes. The focus is on the chemical reactivity and selectivity of transition-metal or metal-free organocatalyst systems. In addition, the working modes of these catalysis will be described primarily on the basis of experimental mechanistic insight.