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Synlett 2005(11): 1740-1742  
DOI: 10.1055/s-2005-871533
LETTER
© Georg Thieme Verlag Stuttgart · New York

Palladium(0)-Catalyzed Cross-Coupling of Fluorous Bis(pinacolato)diboron: An Efficient Access to Fluorous Boronates

Yangen Huanga, Dajun Chena, Feng-Ling Qing*a,b
a Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. China
Fax: +86(21)64166128; e-Mail: flq@mail.sioc.ac.cn;
b College of Chemistry and Chemical Engineering, Donghua University, 1882 West Yanan Lu, Shanghai 200051, P. R. China
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Publication History

Received 21 April 2005
Publication Date:
14 June 2005 (online)

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Abstract

A novel fluorous bis(pinacolato)diboron has been developed as an efficient reagent to prepare fluorous boronates, which are of significance as synthetic equivalents to boronic acids.

Key words

fluorous synthesis - boronates - bis(pinacolato)diboron - Suzuki coupling

6

Analytical data for F-pin2B2 5: IR (thin film): 2987, 1443, 1317, 1240,1209, 1145, 1071 cm-1; 1H NMR (300 MHz, CDCl3): δ = 1.95-2.15 (m, 12 H), 1.11-1.28 (m, 20 H), 0.92-0.99 (m, 12 H), 0.79 (d, J = 15.0 Hz, 2 H); 19F NMR (282 MHz, CDCl3): δ = -81.25 to -81.46 (m, 9 F), -116.60 to -116.70 (m. 6 F), -122.60 (s, 6 F), -123.54 (s, 6 F), -123.84 (s, 6 F), -126.80 (s, 6 F); Anal. Calcd for C60H48B2O4F78Si2 (2390.70): C, 30.14; H, 1.94. Found: C, 30.42; H, 1.79.

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A typical procedure for the cross-coupling reaction of
F-pin2B2 5 with aryl bromide: Fluorous bis(pinacolato)di-boron 5 (359 mg, 0.15 mmol) was added to a solution of arylbromide (1.1 equiv), PdCl2 (dppf) (3% mol), and KOAc (3.0 equiv) in CF3Ph (3 mL) under nitrogen. The mixture was heated to 110 °C and stirred overnight. After removal of the solvent, the residue was dissolved in CH2Cl2 (3 mL) and extracted with FC-77 ( 3 × 3 mL). The fluorous phase was concentrated to afford a mixture of fluorous boronates 6 and fluorous pinacol 1, which could be further isolated by flash chromatography or readily used in the Suzuki cross-coupling reaction.
6a: white waxy solid; mp 49-51 °C; IR (neat): 2985, 1606, 1501, 1442, 1363, 1240, 1207, 1145, 1070, 903 cm-1; 1H NMR: δ = 7.72 (d, J = 7.4 Hz, 2 H), 7.47 (t, J = 7.5 Hz, 1 H), 7.25 (t, J = 7.2 Hz, 2 H), 2.02-2.22 (m, 6 H), 1.40 (d, J = 14.7 Hz, 1 H), 1.37 (s, 9 H), 1.00-1.08 (m, 6 H), 0.87 (d, J = 14.7 Hz, 1 H); 19F NMR: δ = -80.94 (t, J = 7.61 Hz, 9 F), -116.11 (t, J = 16.5 Hz, 6 F), -122.02 (s, 6 F), -122.97 (s, 6 F), -123.30 (s, 6 F), -126.20 to -126.27 (m, 6 F); MS (EI, 70 eV): m/z: 1273 (M + 1+, 3), 1272 (M+, 3), 926 (3), 493 (4), 105 (38), 83 (100); Anal. Calcd for C36H28F39O2BSi: C, 33.98; H, 2.22. Found: C, 33.95; H, 2.36.