Metal-Free Selective Borylation of Arenes by a Diazadiborinine via C–H/C–F Bond Activation and Dearomatization

A newly developed annulated 5-chlorinated
1,3,2,5-diazadiborinine
derivative (4) selectively activates a C–H bond
of benzene (C6H6) and 1,3-di­(trifluoromethyl)­benzene,
as well as a C–F bond in partially fluorinated arenes, to furnish
borylation products under catalyst-, metal-, and irradiation-free
conditions. Moreover, 4 readily undergoes a reversible
dearomative coupling reaction with polycyclic aromatic hydrocarbons
to afford diboration products. The latter represents the first reversible
intermolecular dearomative diboration of arenes.