Triborane (B 3 H 7 )-mediated regioselective substitution reactions of pyridine derivatives.

There exists an interplay between borane and a Lewis base in their adducts. However, studies on these adducts so far have mainly focused on the different reactions of B-H bonds with limited attention given to the influence of borane on the chemistry of the Lewis base, except for BF 3 and BAr 3 . Herein, we have synthesized novel borane adducts with pyridine derivatives, Py·B 3 H 7 , in which the coordination of B 3 H 7 efficiently achieved the intra-molecular charge transfer. The strong B-N bond in these adducts resulted in the formation of stable dearomatic intermediates of pyridine derivatives, confirmed by 1 H and 11 B NMR spectroscopy, from which different reactions have transpired to realize C(sp 3 )-H and C(sp 2 )-H functionalization under mild conditions. The B 3 H 7 pyridine derivatives are stable and do not dissociate or decompose during the reaction process. The high stability of the B-N bond makes this method a good option for boron-containing drugs with potential for use in boron neutron capture therapy (BNCT).