Synthesis of 1,2-Borazaronaphthalenes from Imines by Base-Promoted Borylation of C–H bond

A new
route from benzylic imines permits the synthesis of 1,2-borazaronaphthalenes
in good yields. The reaction involves formation of the enamidyl dibromoborane,
which undergoes base-promoted borylation of the nearby aromatic C–H
bond. Electrophilic attack of the boron species onto the benzylic
arene is supported by the slow borylation of arenes substituted with
electron-withdrawing groups. The resultant boron bromides can be easily
substituted with lithium reagents to provide a range of products.
The electronic properties of these 1,2-borazaronaphthalene derivatives
have been investigated by UV–vis and fluorescence spectroscopy.