Synlett 2015; 26(15): 2175-2179
DOI: 10.1055/s-0035-1560461
letter
© Georg Thieme Verlag Stuttgart · New York

Palladium-Catalyzed Direct Thienylation of Monobromide-Substituted Difluorinated Benzothiadiazoles for Organic Photovoltaics

Qiang Pan
a   College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, P. R. of China   Email: hanshiqing@njtech.edu.cn
,
Chun-Yang He
b   Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, P. R. of China   Email: xgzhang@sioc.ac.cn
,
Shiqing Han*
a   College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, P. R. of China   Email: hanshiqing@njtech.edu.cn
,
Xingang Zhang*
b   Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, P. R. of China   Email: xgzhang@sioc.ac.cn
› Author Affiliations
Further Information

Publication History

Received: 09 June 2015

Accepted after revision: 17 July 2015

Publication Date:
24 August 2015 (online)


Abstract

A palladium-catalyzed cross-coupling between monobromide-substituted difluorinated benzothiadiazoles (DFBT) and simple thiophenes has been developed. The significant feature of this protocol is synthetic simplicity without using toxic stannanes, thus providing a facile access to unsymmetrical DFBT–thiophene structures that are of great interest in organic photovoltaics.

Supporting Information

 
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  • 12 Typical Procedure for Pd-Catalyzed Cross-Coupling of 1a with 2a In a flame-dried Schlenk tube under nitrogen atmosphere, Pd(OAc)2 (2.2 mg, 0.01 mol), dppe (8.0 mg, 0.02 mol), AdOH (54.1 mg, 0.3 mmol), K2CO3 (55.3 mg, 0.4 mmol), and thienylated bromo-DFBT (1a) (86.4 mg, 0.2 mmol) were added, followed by toluene (2 mL) with stirring. Thiophene 2a (67.3 mg, 0.4 mmol) was then added. The reaction mixture was stirred in a preheated oil bath at 120 °C for 12 h. The reaction mixture was cooled to r.t., diluted with CH2Cl2, washed with brine, dried over Na2SO4, filtered, and concentrated. The residue was purified with silica gel chromatography (PE– CH2Cl2, 8:1) to give pure compound 3a.
  • 13 tert-Butyl 5-{5,6-Difluoro-7-(5-hexylthiophen-2-yl)benzo[c]-[1,2,5]thiadiazol-4-yl}thiophene-2-carboxylate (3a) Yield 78 mg (75%); orange solid; mp 112.1 °C. 1H NMR (400 MHz, CDCl3): δ = 8.16 (d, J = 3.6 Hz, 1 H), 8.10 (d, J = 3.6 Hz, 1 H), 7.80 (d, J = 3.2 Hz, 1 H), 6.92 (d, J = 2.8 Hz, 1 H), 2.90 (t, J = 7.6 Hz, 2 H), 1.80–1.72 (m, 2 H), 1.63 (s, 9 H), 1.45–1.39 (m, 2 H), 1.37–1.29 (m, 4 H), 0.91 (t, J = 7.0 Hz, 3 H). 19F NMR (376 MHz, CDCl3): δ = –126.06 (d, J = 14.7 Hz), –129.14 (d, J = 14.7 Hz). 13C NMR (100 MHz, CDCl3): δ = 161.5, 150.9 (dd, J = 262.3 Hz, 19.9 Hz), 150.8 (d, J = 6.7 Hz), 149.0 (dd, J = 260.0 Hz, 20.0 Hz), 148.7 (d, J = 9.3 Hz), 148.6 (d, J = 9.0 Hz), 137.4 (d, J = 6.3 Hz), 137.3 (dd, J = 5.9 Hz, 3.7 Hz), 132.6, 131.6 (d, J = 9.4 Hz), 130.6 (d, J = 9.5 Hz), 128.7 (dd, J = 6.1 Hz, 3.6 Hz), 124.9, 113.2 (d, J = 12.3 Hz), 110.1 (d, J = 12.1 Hz), 82.1, 31.6, 31.5, 30.1, 28.9, 28.3, 22.6, 14.1. MS (MALDI): m/z (%) = 520.1 [M+], 521.1 [M+], 522.1 [M+]. HRMS: m/z calcd for C25H26O2N2F2S3: 520.1119; found: 520.1122.