Regioselective Diversification of 2,1-Borazaronaphthalenes: Unlocking Isosteric Space via C–H Activation

Methods for the regioselective C–H
borylation and subsequent
cross-coupling of the 2,1-borazaronaphthalene core are reported. Azaborines
are dependent on B–N/CC isosterism when employed in
strategies for developing diverse heterocyclic scaffolds. Although
2,1-borazaronaphthalene is closely related to naphthalene in terms
of structure, the argument is made that the former has electronic
similarities to indole. Based on that premise, iridium-mediated C–H
activation has enabled facile installation of a versatile, nucleophilic
coupling handle at a previously inaccessible site of 2,1-borazaronaphthalenes.
A variety of substituted 2,1-borazaronaphthalene cores can be successfully
borylated and further cross-coupled in a facile manner to yield diverse
C(8)-substituted 2,1-borazaronaphthalenes.