Synthesis of dibenzoarsole derivatives from biarylborates <i>via</i> the twofold formation of C–As bonds using arsenium dication equivalents

A strategy for the generation of arsenium dication equivalents from readily available and easy-to-handle phenylarsine oxide and Tf₂O has been developed. The <i>in situ</i>-generated dication equivalent can react with biarylborates to directly produce the corresponding dibenzoarsoles, which are difficult to prepare by other means, <i>via</i> the successive formation of inter- and intramolecular C-As bonds. Furthermore, the unique oxygen atom insertion into the C-As bond in the dibenzoarsole is developed to form the corresponding [1,2]oxarsinine derivative.