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Synlett 2007(5): 0749-0752  
DOI: 10.1055/s-2007-970773
LETTER
© Georg Thieme Verlag Stuttgart · New York

Novel Palladium-Catalyzed Atom-Efficient Cross-Coupling Reaction by Means of Hexaarylcyclotrisiloxane

Mayuko Endoa, Tomoyuki Sakuraia, Satoshi Ojimaa, Takako Katayamaa, Masafumi Unnoa, Hideyuki Matsumotob, Susumu Kowasea, Hiroshi Sanoa, Masanori Kosugi*a, Keigo Fugami*a
a Department of Chemistry, Gunma University, Kiryu, Gunma 376-8515, Japan
Fax: +81(277)301285; e-Mail: fugami@chem.gunma-u.ac.jp;
b Department of Nano-Material Systems, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
Further Information

Publication History

Received 16 December 2006
Publication Date:
08 March 2007 (online)

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Abstract

Hexaarylcyclotrisiloxane, which is one of the most stable derivatives of diarylsilanediol, was found to undergo palladium-catalyzed cross-coupling reaction with aryl halides in good yields. The reaction is performed in an aqueous medium taking potassium hydroxide as an activator. Both of the two aryl groups attached to each silicon atom could be utilized. Some base-sensitive functionality such as acetyl and nitro groups survived the reaction.

Key words

silicon - cross-coupling - palladium - halides - biaryls

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In a mortar were placed diphenylsilanediol (3.2 g, 15 mmol) and PTSA·H2O (7.6 g, 40 mmol), and the mixture was kneaded well for 1 h. After the mixture was allowed to stand for 24 h, the resulting crude product was rinsed with CH2Cl2 and H2O (100 mL each) and the rinse was poured into a separatory funnel. Aqueous layer was extracted with 20 mL of CH2Cl2 and combined organic extract was dried over anhyd Na2SO4. After evaporation of solvent, the crude product was recrystallized from acetone to afford 1a (1.4 g, 2.4 mmol, 48% yield) as colorless plates. The yield could be improved up to 70% when an intermittent kneading was continued after addition of H2O (1.5 mL) for a week prior to the work-up.

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Typical Reaction Procedure.
Hexaphenylcyclotrisiloxane (1a, 59.5 mg, 0.10 mmol) was added to a solution composed of aq KOH solution (3.0 mol dm-3, 1.4 mL, 4.2 mmol) and H2O (0.6 mL) under an argon atmosphere. The mixture was heated to reflux for 1 h. Then, 4-iodoanisole (2b; 112 mg, 0.48 mmol) and Pd(OAc)2 (5.4 mg, 0.024 mmol) were added to the resulting solution, successively. The yellow solution was heated under reflux for 4 h. After the mixture was cooled to r.t. and was extracted with CH2Cl2 (3 × 20 mL). The combined organic layer was dried over anhyd Na2SO4. Silica gel column chromatography after concentration afforded 3a (80.2 mg, 91%).

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All reagents examined were non-hygroscopic white powders, which could be kept under air at r.t. without obvious loss of reactivity.