Photochemical Synthesis and Electrochemical and Photophysical Properties of 2,7-Diarylbenzo[1,2-d:4,3-d′]bis(thiazoles)

Abstract

This article focuses on the development of practical approaches to the preparation of benzo[1,2-d:4,3-d′]bis(thiazoles) using blue light-induced photochemical cyclization of N,N′-(1,4-aryl)dithioamides in the presence of p-chloranil as a mild oxidant. The proposed method allows to obtain benzo[1,2-d:4,3-d′]bis(thiazoles) containing donor substituents in the conjugated chain. Photophysical and (spectro)electrochemical properties of 2,6-di([2,2′-bithiophen]-5-yl)benzo[1,2-d:4,3-d′]bis(thiazole) and -benzo[1,2-d:4,5-d′]bis(thiazole) are studied in detail. The properties of the synthesized compounds suggest their potential applications for organic electronics.

Synthesis, Photophysical, and (Spectro)Electrochemical Properties of New Benzo[1,2-c][1,2,5]thiadiazoles and Benzo[1,2-d][1,2,3]triazoles Fused with Two Thiazole Rings

“…Obviously, such reaction conditions are not suitable for the synthesis of compounds containing thiophene and other easily oxidized donor substituents. It is known that sulfur-containing compounds are capable of photo-oxidative reactions. − We have recently reported that benzobisthiazoles can be obtained by oxidative photocyclization . We studied the possibility of such an approach for the synthesis of compounds 6e and 7e .…”

“…In the spectra of benzotriazole derivatives 7a – 7e , the low-frequency signals overlap each other (compounds 7a , 7b , 7d , and 7e ), and for compound 7c , they are recorded as one broadened signal. The absorption and emission spectra of dithiazolo[4′,5′:3.4;5″,4″:5.6]benzo[1,2-c][1,2,5]thiadiazoles 7a – 7e are similar to the spectra of previously obtained benzothiadiazoles but shifted to the long wavelength region. A bathochromic shift of absorption maxima is observed with an increase in the conjugation system of substituent R, as well as when passing from benzotriazole derivatives 7a – 7e to the corresponding benzothiadiazole derivatives 6a – 6e .…”

“…52−54 We have recently reported that benzobisthiazoles can be obtained by oxidative photocyclization. 55 We studied the possibility of such an approach for the synthesis of compounds 6e and 7e. Photocyclization of thioamides 17e and 18e was carried out under blue light (λ = 440 nm) irradiation in the presence of chloranil as an oxidant (condition A) 55 and under green light (λ = 525 nm) in an air atmosphere using eosin Y (2.0 mol %) as a photocatalyst in the presence of 2 equiv of DIPEA (condition B).…”

“…55 We studied the possibility of such an approach for the synthesis of compounds 6e and 7e. Photocyclization of thioamides 17e and 18e was carried out under blue light (λ = 440 nm) irradiation in the presence of chloranil as an oxidant (condition A) 55 and under green light (λ = 525 nm) in an air atmosphere using eosin Y (2.0 mol %) as a photocatalyst in the presence of 2 equiv of DIPEA (condition B). 56 In both cases (conditions A and B), the reaction products were dithiazolobenzothiadiazole (DTBT) 6e (86 and 58%, respectively) and dithiazolobenzotriazole (DTBTz) 7e (86 and 23%, respectively).…”

Arylation of benzazoles at the 4 positions by activation of their 2-methylsulfinyl groups

“…The arylation is powerful to convert benzobisthiazole 8 through two-fold arylation for the synthesis of 9 (Scheme 2B). This diarylation would be useful for the synthesis of new benzobisthiazole-based materials 12 for organic electronics. Chlorobenzothiazole 1b reacted with resorcinol ( 2j ) to yield the corresponding product 3bj , which underwent Cs 2 CO 3 -mediated S N Ar cyclization to yield tetracyclic aromatic system 10 (Scheme 2C).…”