Dissymmetrization of Benzothiadiazole by Direct C–H Arylation: A Way to Symmetrical and Unsymmetrical Elongated π‐Conjugated Molecules

Abstract

5‐(7‐Bromo‐2,1,3‐benzothiadiazol‐4‐yl)‐2‐thiophenecarbaldehyde is a small building block of great interest for its use in the elaboration of symmetrical or unsymmetrical donor–acceptor π‐conjugated molecules for optoelectronic applications. Herein, a convenient, one‐pot, two‐component synthesis of this intermediate is reported, based upon a palladium‐catalysed, phosphine‐ and additive‐free, direct C–H arylation process. The synthesis has been studied in depth to obtain optimum yields and selectivity by an efficient and environmentally friendly strategy for sustainable synthesis.

Synthesis of Chiral Donor–Acceptor Dyes to Study Electron Transfer Across a Chiral Bridge

“…Acceptor–spacer (A1)–(S) is formed by treating 8 with TMS-acetylene under standard Sonogashira reaction conditions, which yields 9 in 82% (Scheme ).…”

“…13 C NMR gave signals at 1.2 (grease) ppm . Tetrakis­(triphenylphosphine)­palladium(0), tributyl­(3-methylthiophene-2-yl)­stannane ( 3 ), 4,7-dibromobenzo­[ c ]­[1,2,5]­thiadiazole ( 10 ), 3,6-dibromo-9 H -carbazole ( 1 ), 5-(7-bromobenzo­[ c ]­[1,2,5]­thiadiazol-4-yl)­thiophene-2-carbaldehyde ( 8 ), 3,3′-diiodo-2,2′-dimethoxy-1,1′-binaphthalene ( 13­( S )­a ), and 2,2′-dimethoxy-1,1′-binaphthalene ( 12­( S ) ) were synthesized according to the reported literature. 3-Iodo-2,2′-dimethoxy-1,1′-binaphthalene ( 13­( S )­b ) was synthesized in a modified synthetic procedure of the reported literature in improved yields …”

“…1 H-NMR gave signals at 1.52 (water), 1.26 (grease), and 0.08 (grease) ppm. 13 C NMR gave signals at 1.2 (grease) ppm. 29 Tetrakis(triphenylphosphine)palladium(0), 30 tributyl(3-methylthiophene-2-yl)stannane (3), 31 4,7-dibromobenzo [c][1,2,5]thiadiazole (10), 32 3,6-dibromo-9H-carbazole (1), 33 5-(7-bromobenzo [c][1,2,5]thiadiazol-4-yl)thiophene-2-carbaldehyde (8), 34 3,3′-diiodo-2,2′-di- methoxy-1,1′-binaphthalene (13(S)a), 35 and 2,2′-dimethoxy-1,1′binaphthalene (12(S)) 36 were synthesized according to the reported literature.…”

“…All NMR spectra were recorded at 298 K on 400 and 700 MHz Bruker Avance III spectrometers. 1 H and 13 C shifts were referenced to the residual solvent signal (CD 2 Cl 2 , 1 H-NMR: δ = 5.32 ppm, 13 C NMR: δ = 53.84 ppm and CDCl 3 , 1 H-NMR: δ = 7.26 ppm, 13 C NMR: δ = 77.16 ppm). 29 Structural assignments were made with additional information from gCOSY, gHSQC, gHMBC, and gNOESY experiments.…”

“…5-(7-((Trimethylsilyl)ethynyl)benzo [c][1,2,5]thiadiazol-4-yl)thiophene-2-carbaldehyde (9). Under a N 2 atmosphere, 8 (110 mg, 0.34 mmol), 34 TMS-acetylene (95 μL, 0.68 mmol), Pd(PPh 3 ) 4 (8 mg, 0.007 mmol), CuI (6 mg, 0.03 mmol), and NEt 3 (1.2 mL, 8.5 mmol) were dissolved in 15 mL of THF. The reaction mixture was stirred for 5 h at 60 °C using an oil bath.…”