& beta;-Functionalization of 4 a-aza-8 a-boranaphthalene via Iridium-catalyzed C-H Borylation

A general method for the functionalization of 4a-aza-8a-boranaphthalene in the position & beta; to the nitrogen atom has been developed. This method is based on a regioselective iridium-catalyzed C-H activation process for the introduction of a boronate group, which can subsequently be transformed into a variety of aryl or alkynyl groups via cross-coupling reactions. Selective mono- or difunctionalization can be achieved by controlling the reaction conditions during the borylation step. The photophysical properties of the obtained 3- or 3,6-substituted BN-naphthalenes have been evaluated, and some of them have been found to be significantly fluorescent, with fluorescence quantum yields up to 0.85.