Direct arylation polycondensation of β-unprotected chalcogen heteroles under phosphine-free conditions

Publication date: 24 March 2017
Source:Polymer, Volume 113
Author(s): Shotaro Hayashi, Yoshihisa Kojima, Toshio Koizumi
We have demonstrated a direct arylation polycondensation of β-unprotected chalcogen heteroles (furan, thiophene and selenophene) under phosphine-free conditions. The polycondensation of furan and thiophene using a solid-supported palladium catalyst, Pd/C, gave alternating copolymers (Mn = 8000–10000), but the polycondensation of these monomers using common palladium catalysts such as Pd(OAc)2 gave insoluble polymeric products resulting from β-defects and network formation. Selenophene was a less reactive monomer for direct arylation using these catalysts, Pd/C and Pd(OAc)2, yielding low molecular weight copolymer (Mn < 2500). On the other hand, PdCl2 was the most effective catalyst for the polycondensation of selenophene. The high molecular weight polymer (Mn = 11800) could be obtained. The ¹H NMR and UV-vis absorption spectra of the polymers obtained from furan, thiophene and selenophene were similar to those of the polymers synthesized by Suzuki-Miyaura cross-coupling polycondensation.

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