Electronically Driven Regioselective Iridium‐Catalyzed C−H Borylation of Donor‐π‐Acceptor Chromophores Containing Triarylboron Acceptors

We observed a surprisingly high electronically driven regioselectivity for the iridium‐catalyzed C−H borylation of donor‐π‐acceptor (d‐π‐A) systems with diphenylamino (1) or carbazolyl (2) moieties as the donor, bis(2,6‐bis(trifluoromethyl)phenyl)boryl (B((F)Xyl)(2)) as the acceptor, and 1,4‐phenylene as the π‐bridge. Under our conditions, borylation was observed only at the sterically least encumbered para‐positions of the acceptor group. As boronate esters are versatile building blocks for organic synthesis (C−C coupling, functional group transformations) the C−H borylation represents a simple potential method for post‐functionalization by which electronic or other properties of d‐π‐A systems can be fine‐tuned for specific applications. The photophysical and electrochemical properties of the borylated (1‐(Bpin)(2)) and unborylated (1) diphenylamino‐substituted d‐π‐A systems were investigated. Interestingly, the borylated derivative exhibits coordination of THF to the boronate ester moieties, influencing the photophysical properties and exemplifying the non‐innocence of boronate esters.