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Synthesis of cyclic aromatic polymer containing thiophene or pyridine by means of unstoichiometric Suzuki‐Miyaura cyclic polycondensation: Effect of the position of bromine of heteroarylenes on cyclic polycondensation
Author(s) -
Sugita Hajime,
Ohta Yoshihiro,
Yokozawa Tsutomu
Publication year - 2020
Publication title -
journal of polymer science
Language(s) - English
Resource type - Journals
eISSN - 2642-4169
pISSN - 2642-4150
DOI - 10.1002/pol.20200036
Subject(s) - condensation polymer , polymer chemistry , pyridine , thiophene , chemistry , phenylboronic acid , bromine , monomer , polymer , catalysis , organic chemistry
Suzuki‐Miyaura cyclic polycondensation of 1.3 equivalents of thiophene dibromide or pyridine dibromide with 1.0 equivalent of phenylenediboronic acid ester was investigated in the presence of t ‐Bu 3 PPd G2 precatalyst, which generates t ‐Bu 3 PPd(0), and CsF/18‐crown‐6 as a base. Polycondensation of 2,5‐dibromothiophene and 5,5′‐dibromo‐2,2′‐bithiophene with pinacol meta ‐phenylenediboronate ( 2 ) yielded corresponding cyclic polymers. On the other hand, polycondensation of 3,4‐dibromothiophene with para ‐phenylenediboronate ( 5 ) gave linear polymer with bromothiophene at both ends via conventional unstoichiometric polycondensation involving excess dibromo monomer, implying that intramolecular catalyst transfer did not proceed effectively on 3,4‐dibromothiophene. A model reaction of 3,4‐dibromothiophene with phenylboronic acid indeed gave monosubstituted thiophene preferentially via intermolecular catalyst transfer. In the polycondensation of excess pyridine dibromide with 5 , the use of 2,6‐dibromopyridine gave linear polymer, whereas the use of 3,5‐dibromopyridine yielded cyclic polymer. Thus, the position of bromine in heteroarylenes determines whether cyclic polymer or linear polymer is formed, in contrast to the case of unstoichiometric Suzuki‐Miyaura cyclic polycondensation with dibromophenylenes.