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Synlett 2008(20): 3221-3225  
DOI: 10.1055/s-0028-1087244
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Ultrasound-Assisted Synthesis of Symmetrical Biaryls by Palladium-Catalyzed Homocoupling of Aryl n-Butyl Tellurides

Fateh Veer Singha, Hélio A. Stefani*a,b
a Departamento de Farmácia, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, SP - Brazil
b Deprtamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP - Brazil
Fax: +55(11)38154418; e-Mail: hstefani@usp.br;
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Publication History

Received 11 June 2008
Publication Date:
24 November 2008 (online)

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Abstract

An ultrasound-assisted synthesis of symmetrical biaryls with electron-withdrawing or -donating substituents is described and illustrated by palladium-catalyzed homocoupling reaction of aryl tellurides. This procedure offers easy access to biaryls in short reaction time, and the products are achieved in good to excellent yields.

Key words

homocoupling reaction - symmetrical biaryls - aryl n-butyl tellurides

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General Experimental Procedure for Biaryls 2a-h and 4a-c
A suspension of aryl telluride (1a, 0.135 g, 0.5 mmol), Pd(PPh3)4 (0.45 g, 8 mmol), Na2CO3 (0.106 g, 1 mmol) and Ag2O (0.116 g, 0.5 mmol) in MeOH (3 mL) was irradiated in a water bath of an ultrasonic cleaner for 45 min. Then, the reaction was diluted with EtOAc (30 mL). The organic layer was washed with sat. solution of NH4Cl (2 × 10 mL) and H2O (2 × 10 mL), dried over MgSO4, and concentrated under vacuum. The crude product was purified by flash silica column chromatography using hexane as eluent and characterized as biphenyl 2a. Compound 2a: white solid; mp 70-72 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 7.13-7.28 (m, 6 H, ArH), 7.45 (d, J = 7.2 Hz, 4 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 122.6, 126.95, 130.11, 141.61. GC-MS (%): 154 (100), 153 (57), 152 (39), 76 (44).
Compound 2b: white solid; mp 146-148 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 7.38 (d, J = 8.0 Hz, 4 H, ArH), 7.45 (d, J = 8.0 Hz, 4 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 128.00, 129.12, 133.52, 138.20. GC-MS (%): 222 (100), 152 (63), 93 (21), 75 (47).
Compound 2c: white solid; mp 172-174 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 3.84 (s, 6 H, 2 OMe), 6.95 (d, J = 8.4 Hz, 4 H, ArH), 7.47 (d, J = 8.4 Hz, 4 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 54.89, 113.70, 127.28, 133.04, 158.24. GC-MS (%): 214 (100), 199 (87), 171 (21), 128 (16).
Compound 2d: white solid; mp 122-124 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 2.33 (s, 6 H, 2 Me), 6.96 (d, J = 7.6 Hz, 4 H, ArH), 7.64 (d, J = 7.6 Hz, 4 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 20.93, 127.28, 129.94, 137.88, 138.76. GC-MS (%): 182 (68), 167 (100), 165 (45), 152 (19), 89 (21).
Compound 2e: white solid; mp 160-162 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 7.41 (d, J = 8.2 Hz, 4 H, ArH), 7.48 (d, J = 8.2 Hz, 4 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 128.23, 129.05, 133.76, 138.45. GC-MS (%): 312 (66), 152 (89), 76 (100).
Compound 2f: colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 2.08 (s, 6 H, 2 Me), 7.02 (t, J = 8.4 Hz, 2 H, ArH), 7.18 (t, J = 8.4 Hz, 4 H, ArH), 7.50 (d, J = 8.0 Hz, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 22.70, 124.74, 127.02, 127.10, 130.62, 132.13, 137.65. GC-MS (%): 182 (77), 167 (100), 166 (22), 165 (48).
Compound 2g: colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 7.38 (t, J = 7.8 Hz, 2 H, ArH), 7.58 (d, J = 7.8 Hz, 2 H, ArH), 7.70 (d, J = 7.8 Hz, 2 H, ArH), 7.80 (s, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 121.39, 122.71, 123.80, 130.34, 131.80, 134.95. GC-MS (%): 290 (100), 271 (24), 201 (28), 152 (19), 89 (21).
Compound 2h: colorless oil. ¹H NMR (300 MHz, CDCl3): δ = 2.02 (s, 6 H, 2 Me), 6.86-7.05 (m, 6 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 22.99, 114.48, 117.77, 118.89, 133.34, 139.93, 160.12, 163.37. GC-MS (%): 218 (92), 203 (100), 201 (52), 183 (60).
Compound 3a: white solid; mp 138-140 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 7.20 (t, J = 7.8 Hz, 2 H, ArH), 7.36-7.52 (m, 4 H, ArH), 7.66-7.76 (m, 6 H, ArH), 8.18 (d, J = 8.4 Hz, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 122.94, 126.26, 126.78, 127.19, 127.42, 128.02, 128.40, 129.99, 132.09, 134.56. GC-MS (%): 254 (90), 253 (100), 252 (80), 250 (25), 126 (98), 125 (47).
Compound 3b: white solid; mp 180-182 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 7.44-7.58 (m, 6 H, ArH), 7.66-7.83 (m, 6 H, ArH), 8.00 (s, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 119.37, 125.84, 126.45, 126.57, 127.42, 128.80, 129.15, 129.49, 131.39, 134.06. GC-MS (%): 254 (100), 252 (34), 126 (25). Compound 3c: white solid; mp >250 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 3.85 (s, 6 H, 2 OMe), 7.03 (s, 2 H, ArH), 7.10 (d, J = 9.0 Hz, 2 H, ArH), 7.44 (d, J = 9.0 Hz, 2 H, ArH), 7.50-7.60 (m, 4 H, ArH), 7.85 (s, 2 H, ArH). ¹³C NMR (75.5 MHz, CDCl3): δ = 55.11, 105.56, 116.83, 119.57, 128.18, 128.29, 129.40, 129.45, 129.81, 132.85, 157.69. GC-MS (%): 314 (100), 299 (29), 271 (29), 228 (25), 157 (25).