Synlett 2003(3): 0361-0364
DOI: 10.1055/s-2003-37117
LETTER
© Georg Thieme Verlag Stuttgart · New York

An Efficient Palladium-Catalyzed Synthesis of Unsymmetrical Diaryl Sulfones from Aryl Bromides/Triflates and Arenesulfinates

Sandro Cacchi*, Giancarlo Fabrizi, Antonella Goggiamani, Luca M. Parisi
Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università degli Studi ‘La Sapienza’, P.le A. Moro 5, 00185 Roma, Italy
Fax: +39(6)49912780; e-Mail: sandro.cacchi@uniroma1.it;
Further Information

Publication History

Received 21 November 2002
Publication Date:
07 February 2003 (online)

Abstract

The palladium-catalyzed coupling of arenesulfinate salts and aryl bromides or triflates provides a simple and extremely efficient route to unsymmetrical diaryl sulfones. The reaction was found to be strongly influenced by the presence of n-Bu4NCl. The ammonium salt tends to favor the formation of sulfones with neutral, electron-rich and slightly electron-poor aryl bromides or trif­lates and to hamper the reaction with electron-poor aryl bromides or triflates.

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Cacchi, S.; Fabrizi, G.; Goggiamani, A.; Parisi, L. M. Org. Lett., in press.

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Typical Procedure for the Preparation of Unsymmetrical Diaryl Sulfones with Electron-Poor Aryl Bromides or Triflates (Procedure B) (Table 2, Entry 28): In a Carousel Tube Reaction (Radley Discovery), to a solution of sodium p-toluenesulfinate (0.075 g, 0.420 mmol) and p-nitrophenyl bromide (0.0707 g, 0.350 mmol) in 2.0 mL of toluene under argon, Pd2(dba)3 (0.008 g, 0.009 mmol), Xantphos (0.010 g, 0.018 mmol) and Cs2CO3 (0.171 g, 0.525 mmol) were added. The mixture was warmed at 120 °C under stirring for 5 h. After cooling, the reaction mixture was diluted with ethyl acetate, washed with water, dried over Na2SO4 and concentrated under reduced pressure. The reaction mixture was purified by chromatography (silica gel, 35 g; n-hexane/ethyl acetate 80/20 v/v) to give 0.076 g of p-nitrophenyl p-tolyl sulfone (78% yield): Mp 164-165 °C. IR (KBr): 2926, 1351, 1157 cm-1. 1H NMR (CDCl3): δ = 8.31 (d, J = 8.9 Hz, 2 H), 8.10 (d, J = 8.9 Hz, 2 H), 7.84 (d, J = 8.4 Hz, 2 H), 7.34 (d, J = 8.1 Hz, 2 H), 2.41 (s, 3 H). 13C NMR (CDCl3): δ = 150.3, 147.9, 145.5, 137.1, 130.4, 128.9, 128.2, 124.5, 21.7. Anal Calcd for C13H11O4S: C, 56.31; H, 4.00. Found: C, 56.23; H, 3.99.
With neutral, electron-rich and slightly electron-poor aryl bromides or triflates, 1.2 equiv of n-Bu4NCl were added (procedure A).