Recently, a manuscript for a paper on which I am a co-author was submitted for publication. The work presented in this manuscript describes Pd-catalyzed C-H activation chemistry, which offers an easier and less toxic alternative to traditional cross coupling reactions. This approach is especially suitable for electron poor substrates, as it turns a synthetic weakness into a strength!
Electron-poor building blocks are important components of π-conjugated materials, but are often poor substrates for conventional cross-coupling methodologies; however, their electron paucity favors their use in C-H activation reactions. Here diarylation of 5,6-dicyano[2,1,3]benzothiadiazole (DCBT) is demonstrated using both C-H/C-Br and C-H/C-H couplings. The former approach is particularly high yielding with a variety of (hetero)aryl bromides, and has been extended to related benzodiimine acceptors including 5,6-dicyanobenzo[1,2,3]triazole, 6,7-dicyanoquinoxaline, and 6,7-dinitroquinoxaline, suggesting the general applicability of this chemistry to electron-poor building blocks. The high yields of the C-H/C-Br coupling reactions have been exploited in the incorporation of DCBT into conjugated polymers. DCBT is a considerably stronger acceptor than many other benzodiimine derivatives, which together with its ease of C-H functionalization, may make it a useful building block for conjugated materials.
Why Our C-H Activation is Interesting
C-H bonds are typically considered unreactive. Research in C-H activation shows that the C-H bond can be cleaved by coordination, which translates to the potential conversion of cheap and abundant alkanes into functionalized, organic compounds.
“We believe this work will inspire a wider adoption of C-H activation in materials chemistry, and that the dicyanothiadiazole acceptor may – as a result of its facile (hetero)arylation and its powerful acceptor character – become a widely used building block for materials.”
– Dr. Seth Marder, Principal Investigator