Synthesis of Pyrrole-Based Poly(arylenevinylene)s via Co-Catalyzed Hydroarylation of Alkynes

Molecular Design of Naphthalene- and Carbazole-Based Monomers for Regiospecific Synthesis of Poly(arylenevinylene)s via Co-Catalyzed Hydroarylation Polyaddition

This study focuses on the development of regiospecific hydroarylation polyaddition of naphthalene- and carbazole-based monomers with diynes under mild reaction conditions at room temperature. A 1-pyrazole substituent serves as an appropriate directing group for a Co-catalyst to efficiently activate the C-H bonds of generally inactive six-membered aromatic hydrocarbons. The 1-pyrazole groups in 2,6-di(1-pyrazolyl)naphthalene adopt planar conformations and act as directing groups, resulting in a smooth hydroarylation reaction. In contrast, the reaction with 1,5-di(1-pyrazolyl)naphthalene do not proceed. The polyaddition reaction of 2,6-di(1-pyrazolyl)naphthalene selectively proceeds at 3,7-positions under mild reaction conditions at 30 °C, and yields corresponding poly(arylenevinylene) (PAV) with high molecular weight. This molecular design is also applicable to the hydroarylation polyaddition of carbazole; the polyaddition reaction of 9-(2-ethylhexyl)-3,6-di(1-pyrazolyl)carbazole selectively occurred at 2,7-positions. The optical and electronic properties of the synthesized compounds are evaluated. The obtained PAVs serve as an emitting material in organic light-emitting diode (OLED). This study aims to develop a Co-catalyzed hydroarylation polyaddition via C-H activation of generally inactive polyaromatic hydrocarbons (PAHs) under mild conditions.

Regioselective Synthesis of Pyrrole-Based Poly(arylenevinylene)s via Mn-Catalyzed Hydroarylation Polyaddition

Mn-catalyzed hydroarylation polyaddition of 1-(2-pyrimidinyl)pyrrole (1a) with aromatic diynes is investigated. The use of commercially available MnBr(CO)5 as a precatalyst under the optimized reaction conditions resulted in a site- and regioselective hydroarylation polyaddition, affording the corresponding poly(arylenevinylene)s (PAVs) with excellent vinylene selectivity. The reaction protocol eliminates the production of stoichiometric amounts of byproducts from the monomers. The nonstoichiometric polyaddition of an excess amount of 1a with aromatic diynes is also demonstrated. The 2-pyrimidinyl substituent promoted the intramolecular transfer of the Mn catalyst walking through the 1a moiety.

Halogen-, oxidant- and directing group-free synthesis of donor-acceptor type conjugated polymers

An intermolecular hydrogen migration from dibutadienylpyridine to dialkynylthiophene catalysed by [Ru(η6-naphthalene)(η4-oxa-bnd)] (oxa-bnd = 9-oxabicyclo[3.3.1]nona-2,6-diene) produces poly(dialkynylthiophene-alt-dibutadienylpyridine). The exact alternating copolymerisation nature is shown by MALDI-TOF MS.

Synthesis of Poly(arylenevinylene)s by Rhodium-Catalyzed Stitching Polymerization/Alkene Isomerization

Poly(arylenevinylene)s constitute an important class of π-conjugated polymers for their potential utility as optoelectronic materials. Herein, we developed a sequence of rhodium-catalyzed stitching polymerization of 1,2-dialkynyl(hetero)arenes and aromatization-driven alkene isomerization for the synthesis of new poly(arylenevinylene)s. The polymerization and subsequent alkene isomerization proceeded smoothly with high degree of stitching efficiency by employing a Rh/tfb complex as the catalyst, and not only diynes but also triynes and tetraynes could be polymerized to give poly(arylenevinylene)s that are not easily accessible by existing synthetic methods. The polymers obtained by the present method were thermally stable, and their optical properties could be varied depending on the repeating unit structure.

Nonstoichiometric hydroarylation polyaddition for synthesis of pyrrole-based poly(arylenevinylene)s

Nonstoichiometric polyaddition via the Co-catalyzed hydroarylation of diyne monomers with excess 1-(2-pyrimidinyl)pyrrole was demonstrated.