Direct (hetero)arylation: a new tool for polymer chemists

Multicomponent syntheses of functional chromophores

Multicomponent reactions are a valuable tool for the synthesis of functional π-electron systems. Two different approaches can be taken into account for accessing the target structures. In the more conventional scaffold approach an already existing chromophore is coupled with other components to give a complex functional π-system. Here, electronically monotonous components can also be introduced, which may exert synergistic electronic effects within the novel compound. The more demanding chromophore concept generates a complete π-electron system and a scaffold concurrently. The latter approach is particularly stimulating for methodologists since π-systems might be accessible from simple starting materials. This review encompasses the advances in the preparation of functional π-electron systems via multicomponent processes during the past few years, based both on the scaffold and chromophore concepts. Besides the synthetic strategies the most important properties, i.e. redox potentials, absorption and emission maxima or fluorescence quantum yields, of the synthesized molecules are highlighted.

Ruthenium-catalyzed direct arylations with aryl chlorides

Aryl chlorides are readily available at lower cost than the corresponding bromides and iodides, but are much more challenging as substrates in metal-catalyzed cross-couplings.

Cobalt-catalyzed chelation assisted C–H allylation of aromatic amides with unactivated olefins

The reaction of aromatic amides with unactivated olefins in the presence of Co(OAc)₂ gave allylated products, not vinylated products.

Direct arylation of fluoroarenes toward linear, bent-shaped and branched π-conjugated polymers: polycondensation post-polymerization approaches

A direct arylation polycondensation of fluoroarenes with 2,7-dibromo-9,9-dioctylfluorene,F8, was achieved in a low polar solvent, toluene.

Structural effects of dibromocarbazoles on direct arylation polycondensation with 3,4-ethylenedioxythiophene

Microwave-assisted direct arylation polycondensation of 3,4-ethylenedioxythiophene produced a solution processable and electrochromic polymer when 3,6-dibromocarbazole was employed as a comonomer.

Direct arylation polymerization towards narrow bandgap conjugated microporous polymers with hierarchical porosity

Conjugated microporous polymers are synthesized via facile direct arylation polymerization, resulting in conjugated networks with hierarchical porosity and a narrow bandgap of 1.5 eV.

Structure–properties relationship in diketopyrrolopyrrole based small molecules using functional terminal side chains via direct arylation: a joint experimental and theoretical study

The role of terminal side chains in diketopyrrolopyrrole based small molecules has been analyzed, demonstrating how their optoelectronic properties vary.

Dramatically different charge transport properties of bisthienyl diketopyrrolopyrrole-bithiazole copolymers synthesized via two direct (hetero)arylation polymerization routes

Two diketopyrrolopyrrole-bithiazole copolymers with same building blocks synthesized via direct (hetero)arylation polymerization through different routes show dramatically different charge transport properties.

Highly regioselective meta arylation of oxalyl amide-protected β-arylethylamine via the Catellani reaction

A first bidentate directing group assisted highly selective meta arylation of β-arylethylamine derivatives with various iodides is reported.

Direct C–H arylation for various Ar-cored diketopyrrolopyrrole containing small molecules in solution-processed field-effect transistors

D–A–π–A–D small molecules Ar(DPPT₂)₂ are designed and synthesized by direct (hetero) C–H arylation, with hole mobility as high as 0.12 cm² V⁻¹ s⁻¹.

Regioselectivity in palladium-catalysed direct arylation of 5-membered ring heteroaromatics

In the past few years, several results using modified catalysts and new reaction conditions have been reported permitting better control of the regioselectivity of Pd-catalysed arylations.

Palladium-catalyzed oxidative direct arylation polymerization (Oxi-DArP) of an ester-functionalized thiophene

A palladium-catalyzed dehydrogenative polycondensation is reported, resulting in high quality polymers from an unsymmetrical ester-containing monomer without preactivation.

Synthesis of benzothiadiazole-based molecules via direct arylation: an eco-friendly way of obtaining small semi-conducting organic molecules

Direct arylation proves to be a greener way than other classical methods for the coupling of benzothiadiazole with thiophene carboxaldehyde.

Regioselective copper-diamine-catalyzed C–H arylation of 1,2,4-triazole ring with aryl bromides

A bench-top protocol using simple Cu-diamine catalysis for the regioselective C5–H arylation of 1,2,4-triazole ring with (hetero)aryl bromides.

Simple synthesis of novel terthiophene-based D–A1–D–A2 polymers for polymer solar cells

Our study presents a simple synthetic route to a series of novel terthiophene-based D–A₁–D–A₂ polymers for efficient PSCs.

Narrow bandgap thienothiadiazole-based conjugated porous polymers: from facile direct arylation polymerization to tunable porosities and optoelectronic properties

Conjugated porous polymers with narrow bandgaps, tunable morphologies, porosities and optoelectronic properties are synthesized via facile direct arylation polymerization.

High Mobility Ambipolar Diketopyrrolopyrrole-Based Conjugated Polymer Synthesized Via Direct Arylation Polycondensation

A diketopyrrolopyrrole-based conjugated polymer, PDPP-4FTVT, which exhibits ambipolar transport behavior in air with hole and electron mobilities up to 3.40 and 5.86 cm(2) V(-1) s(-1), respectively, is synthesized via direct arylation polycondensation. Incorporation of F-atoms in β-positions of thiophene rings dramatically improves the efficiency of direct arylation polycondensation.

2-Octyl thiophene based three ring mesogens: solid state (13)C NMR and XRD investigations

2-Octyl thiophene based three-ring mesogens namely 4-n-alkoxyphenyl 4-(5-n-octyl-2-thienyl)benzoates are synthesized by employing palladium acetate based direct arylation. The alkoxy terminal is varied with even carbons from C2 to C14 and enantiotropic polymesomorphism is noticed for all the homologs. Accordingly, phase sequence consisting of nematic, smectic A, smectic C and smectic B is seen for mesogens with terminal chains C6, C8, C10 and C12 on cooling the isotropic phase. For mesogens with C2, C4, C8 and C10 terminal alkoxy chains, the mesophase assignment from hot-stage optical microscopy and differential scanning calorimetry is further confirmed by variable temperature powder X-ray diffraction measurements. The appearance of smectic B phase is established by noticing sharp and intense peaks in both small-angle and wide-angle regions. For a representative mesogen, i.e. T10, high-resolution solid-state (13)C NMR investigations are carried out in all the phases, viz. nematic, smectic A, smectic C and smectic B phases. The orientational order parameters calculated from (13)C-(1)H dipolar couplings from 2D SAMPI-4 experiments are found to be 0.44, 0.67, 0.73 and 0.79 in nematic, smectic A, smectic C and smectic B mesophases for the center phenyl ring respectively. Remarkably, the thiophene order parameter in all mesophases is found to be higher than that of phenyl rings and is explained by considering the molecular shape, which has a terminal bend. Further, the mesogens are found to be photoemissive in chloroform solution with an emission band at ∼410 nm.

Enabling high-mobility, ambipolar charge-transport in a DPP-benzotriazole copolymer by side-chain engineering

In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit.

In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit. We demonstrate that the BTZ unit allows for additional solubilizing side-chains on the co-monomer and show that the introduction of a linear side-chain on the DPP-unit leads to an increase in thin-film order and charge-carrier mobility if a sufficiently solubilizing, branched, side chain is attached to the BTZ. We compare two different synthetic routes, direct arylation and Suzuki-polycondensation, by a direct comparison of polymers obtained via the two routes and show that direct arylation produces polymers with lower electrical performance which we attribute to a higher density of chain Furthermore we demonstrate that a polymer utilizing this design motif and synthesized via Suzuki-polycondensation ((l-C₁₈)-DPP-(b-C₁₇)-BTZ) exhibits exceptionally high and near balanced average electron and hole mobilities >2 cm² V^–1 s^–1 which are among the highest, robustly extracted mobility values reported for DPP copolymers in a top-gate configuration to date. Our results demonstrate clearly that linear side chain substitution of the DPP unit together with co-monomers that allow for the use of sufficiently long or branched solubilizing side chains can be an attractive design motif for solution processable, high mobility DPP copolymers.

A palladium-catalysed multicomponent coupling approach to conjugated poly(1,3-dipoles) and polyheterocycles

Conjugated polymers have emerged over the past several decades as key components for a range of applications, including semiconductors, molecular wires, sensors, light switchable transistors and OLEDs. Nevertheless, the construction of many such polymers, especially highly substituted variants, typically involves a multistep synthesis. This can limit the ability to both access and tune polymer structures for desired properties. Here we show an alternative approach to synthesize conjugated materials: a metal-catalysed multicomponent polymerization. This reaction assembles multiple monomer units into a new polymer containing reactive 1,3-dipoles, which can be modified using cycloaddition reactions. In addition to the synthetic ease of this approach, its modularity allows easy adaptation to incorporate a range of desired substituents, all via one-pot reactions.

The requirement for multistep synthesis can render the fabrication of highly substituted polymers particularly troublesome. Here, the authors take advantage of metal-catalysed multicomponent polymerization to synthesize a large family of such materials with ease from single-pot reactions.