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Synthesis of highly soluble fluorescent π-extended 2-(2-thienyl)benzothiazole derivatives via oxidative cyclization of 2-thienylthioanilide as the key step

We report the synthesis of highly soluble push–pull type fluorescent 2-(2-thienyl)benzothiazole dyes and the evaluation of their photophysical properties. The key step is the synthesis of the 2-(5′-bromothien-2′-yl)-6-alkoxybenzothiazole via oxidative cyclization of 2-thienylcarbothioamide using PhI...

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Bibliographic Details
Published in:Tetrahedron letters 2013-12, Vol.54 (52), p.7103-7106
Main Authors: Ji, Sanghoon, Shigeta, Masayuki, Niko, Yosuke, Watanabe, Junji, Konishi, Gen-ichi
Format: Article
Language:English
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Summary:We report the synthesis of highly soluble push–pull type fluorescent 2-(2-thienyl)benzothiazole dyes and the evaluation of their photophysical properties. The key step is the synthesis of the 2-(5′-bromothien-2′-yl)-6-alkoxybenzothiazole via oxidative cyclization of 2-thienylcarbothioamide using PhI(OAc)2 as an oxidant. In this Letter, we synthesize highly soluble push–pull type fluorescent 2-(2-thienyl)benzothiazole dyes and evaluate their photophysical properties. The key step is the synthesis of 2-(5′-bromothien-2′-yl)-6-alkoxybenzothiazole (2) via oxidative cyclization of 2-thienylthioanilide using PhI(OAc)2 as the oxidant. The target dyes could be easily synthesized by the Suzuki–Miyaura cross-coupling reaction of 2 and an appropriate π-donor. The photophysical properties of the 2-thienylbenzothiazole chromophore were controlled by the π-donor moiety. It was found that 2 exhibited large Stokes shifts (5345cm−1) and a high quantum efficiency for fluorescence (ΦF=0.94 in CH2Cl2). Therefore, it can be expected to be a useful photofunctional material in liquid crystal laser dyes and nonlinear optical materials.
ISSN:0040-4039
1873-3581
DOI:10.1016/j.tetlet.2013.10.071