Efficient Modular Synthesis of Substituted Borazaronaphthalene

A highly efficient modular synthetic
method for BN-fused polycyclic
aromatic hydrocarbons (PAHs) composed of a borazaronaphthalene core along with multiple functionalized
sites is reported. The halogenated 2,1-borazaronaphthalene cores are
constructed through a ring-closing reaction between o-ethynylaniline derivatives and boron halides. The controllable halogen
substituents make further derivatization of 2,1-borazaronaphthalene
cores feasible by using metal-catalyzed cross-coupling reactions.
On the basis of the carefully designed precursors, various functional
aromatic rings can be fused to the azaborine core via a one-pot nucleophilic
tandem reaction, affording previously inaccessible PAHs in moderate
yields.