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Pd‐Catalyzed Consecutive C−H‐Arylation‐Triggered Cyclotrimerization: Synthesis of Star‐Shaped Benzotristhiazoles and Benzotrisoxazoles
Author(s) -
Xu Zhanqiang,
Oniwa Kazuaki,
Kikuchi Hiromasa,
Bao Ming,
Yamamoto Yoshinori,
Jin Tienan,
Terada Masahiro
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201801849
Subject(s) - trimer , molecule , thiazole , conjugated system , star (game theory) , catalysis , materials science , discotic liquid crystal , fluorescence , photochemistry , polymer , combinatorial chemistry , chemistry , stereochemistry , organic chemistry , physics , optics , dimer , astrophysics , composite material
Star‐shaped π‐extended molecules comprising discotic aromatic cores and peripheral π‐conjugated arms have attracted significant attention as diverse optoelectronic materials in terms of their large π‐surface, tunable self‐assembly, enhanced charge transport and fluorescence, and liquid crystallinity. Although many efforts have been made in the construction of various aromatic discotic cores, a new class of C 3 ‐symmetric star‐shaped discotic π‐molecules consisting of electron‐deficient benzotristhiazole and benzotrisoxazole cores, which are expected to exhibit distinct optoelectronic properties, remains unexplored owing to the unachievable synthetic approaches involved in their synthesis. Herein, we report a novel and highly efficient Pd‐catalyzed cyclotrimerization of the functionalized thiazoles or oxazoles for the construction of a new class of discotic molecules of benzotristhiazole and benzotrisoxazole central cores with star‐shaped π‐conjugated arms. The combination of [Pd 2 (dba) 3 ]/XPhos (dba=dibenzylideneacetone) catalyst systems with the 4‐bromo‐substituted thiazole enables the formation of a sufficiently stable thiazole–Pd species that participates in the subsequent C−H arylations consecutively to form the corresponding cyclic trimer products. This new class of star‐shaped discotic π‐extended products showed tunable energy levels and high fluorescence quantum yields that make them promising candidates for optoelectronic applications.