ABSTRACT
As the Handbook makes clear, the large-scale applications of conjugated polymers are manifold. Unfortunately, in many cases, their production is restricted by the costs associated with their synthesis. 1 The direct (hetero)arylation polymerization (DHAP) reaction, which harnesses the single-step activation and arylation of aromatic carbon-hydrogen bonds, is an attractive alternative for the efficient synthesis of conjugated polymers. This palladium-catalyzed, base-assisted technique allows for the formation of a bond between two sp 2 -carbon atoms via the condensation of the carbon-halogen (C–X) bond of one arene (or heteroarene) with the carbon-hydrogen (C–H) bond of another. This contrasts with the traditional cross-coupling techniques which have been adapted to polymer synthesis, which require either ex situ bond pre-functionalization, for example with organotin and organoboron compounds (in the case of Migita–Stille and Miyaura–Suzuki reactions, respectively), or in situ bond modification, such as with organozinc and organomagnesium (for the Negishi and Kumada–Corriu couplings). 2–5 The former class is illustrated in Figure 5.1, where the organometallic functional group could be either -SnR3 or -B(OR)2 in the case of ex situ metalation, used primarily for copolymerizations, whereas –ZnX and –MgX are used for in situ metalation of monomers for homopolymerizations.196 DHAP: a shortcut to conjugated polymers. A comparison of the Miyaura–Suzuki, Migita–Stille, and direct (hetero)arylation cross-coupling techniques for the synthesis of a hypothetical polymer. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9781315159522/ab60430e-1b37-4c27-9089-7b3e8b4c996e/content/fig5_1_B.tif"/>
