This document discusses the use of C-H functionalization catalysis to incorporate electron-deficient moieties into conjugated materials without needing to first install reactive halides or stannanes. Electron-deficient moieties are important for electronic materials as they can tune optical properties and transport characteristics. Direct C-H functionalization avoids harsh halogenation steps and bypasses instability issues of stannanes. Examples are given of one-pot syntheses using this approach to obtain up to 96% yields of differentially substituted electron-accepting building blocks. Challenges include controlling reaction selectivity when multiple C-H bonds on a moiety could potentially react.

1. Organic Pedagogical Electronic
Network
C–H Functionalizations on Electron-
deficient Aromatics in the Synthesis
of p-conjugated Materials
The Marder Group
Georgia Institute of Technology

2. Introduction
1) Lafrance, M.; Rowley, C.; Woo, T.; Fagnou, K.; J. Am. Chem. Soc., 2006, 8754.
Use C-H activation catalysis so that
the e- deficient coupling partner
does not have to be a Stille reagent
or a halogenated aromatic
Why electron accepting moieties?
 Required for e- transport materials
 Can form potentially air stable
anions
 Can be used to tune optical
absorption properties in materials
for organic photovoltaic systems
 Can help to ionization potential
and electron affinity in materials
Challenges
 Typically use Stille or Suzuki coupling to
incorporate e- deficient moiety:
M Ar¹ M X Ar² X
X = Br, I, OTfM = Sn or B
Pd
Ar¹ Ar²
n
a polymer
+
If Ar1 is e- deficient:
 Often unstable with Sn
 Inefficient coupling
If Ar2 is e- deficient:
 Harsh halogenation
 Synthesis difficult
Seminal Example:1

3. Electron Accepting Building Blocks
1) Zhang, J.; Chen, W.; Rojas, A. J.; Jucov, E. V.; Timofeeva, T. V.; Parker, T. C.; Barlow, S.; Marder, S. R. J. Am. Chem. Soc. 2013, 135, 16376.
2) He, C.; Wu, C.; Zhu, Y.; Zhang, X. Chem. Sci., 2014, DOI: 10.1039/C3SC53119H.
18 examples
up to 96% yield
differentially
substituted, one-
pot
Some good e- accepting building blocks:
Developed Examples:1,2

4. Directed C–H Functionalization
1) Glauco Battagliarin, et al.,Org. Lett., 2011, 3012.
2) Zhang, J.; Singh, S.; Hwang, D. K.; Barlow, S.; Kippelen, B.; Marder, S. R. J. Mater. Chem. C 2013, 1, 5093.

5. Problems
1) Tani, S.; Uehara, T. N.; Yamaguchi, J.; Itami, K. Chem. Sci., 2014, 5, 123–135.
1. The acidity of C-H bond in e- poor accepting blocks affects its reactivity
towards direct activation. Predict which one, a or b, is the main product of the
following reaction and explain why.
2. Thiazole-based moieties are important building blocks for organic
electronic materials. Theoretically, all three C-H bonds can be directly
activated by transition metal catalysis, which brings up a reaction selectivity
issue. Rationalize the following regioselectivity.1

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Contributed by:
The Marder Group, 2014
Georgia Institute of Technology