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Synlett 2010(18): 2733-2736  
DOI: 10.1055/s-0030-1258815
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© Georg Thieme Verlag Stuttgart ˙ New York

Ligand-Free Palladium-Catalyzed C-S Coupling Reactions Using Water as Solvent and Microwaves

Sivan Velmathi*a,b, Reena Vijayaraghavana, Ch. Amarendara, Ravindra P. Palb, Ajayan Vinub
a Organic and Polymer Synthesis Laboratory, Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015, India
b International Center for Materials Nanoarchitectonics, World Premier International (WPI) Research Initiative, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
Fax: +91(431)2500133; e-Mail: velmathis@nitt.edu;
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Publikationsverlauf

Received 26 July 2010
Publikationsdatum:
08. Oktober 2010 (online)

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Abstract

Herein we demonstrate for the first time a rapid and efficient method for the synthesis of aryl sulfides by the direct substitution reaction of aromatic thiols with aryl halides using water as solvent under microwave irradiation. This procedure offers a high yield in shorter reaction time as compared to conventional methods.

Key words

C-S coupling - aryl halides - thiols - microwave - palladium acetate

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Typical Procedure
In a Teflon-coated 50 mL vessel was placed 4-iodo-acetophenone (0.246 g, 1 mmol), of 4-aminothiophenol (0.125 g, 1 mmol), of Pd(OAc)2 (11 mg, 5 mol%), NaF (42 mg, 1 mmol), tetrabutylammonium bromide (TBAB, 0.323 g, 1 mmol), and H2O (15 mL), and the vessel was placed inside the microwave cavity (Milestone Synth) Initial microwave irradiation of 150 W was used, the temperature being increased to 150 ˚C and held without agitation at this temperature for 20 min. During this time, the power was modulated automatically to hold the reaction mixture at 150 ˚C. After allowing the mixture to cool to r.t., the reaction vessel was opened and the contents poured into a separating funnel. Water (30 mL) and Et2O (30 mL) were added, and the organic material extracted and removed. After further extraction of the aqueous layer, combining the organic washings, and drying them over MgSO4, the Et2O was removed in vacuo leaving the crude product that was then purified as appropriate.