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Synlett 2006(9): 1431-1433  
DOI: 10.1055/s-2006-941576
LETTER
© Georg Thieme Verlag Stuttgart · New York

Preparation of Silyl Esters by ZnCl2-Catalyzed Dehydrogenative Cross-Coupling of Carboxylic Acids and Silanes

Guo-Bin Liu*
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, P. R. of China
Fax: +86(21)65642261; e-Mail: liuguobin@fudan.edu.cn;
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Publikationsverlauf

Received 19 February 2006
Publikationsdatum:
22. Mai 2006 (online)

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Abstract

An efficient route to silyl esters by dehydrogenative cross-coupling of silanes and carboxylic acids was investigated. Treatment of silanes and carboxylic acids in the presence of 15mol% of ZnCl2 in DMF at 120 °C afforded the corresponding ­silyl esters in good yields under relatively mild conditions.

Key words

silyl esters - zinc chloride - silanes - carboxylic acids

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Typical Procedure.
To a mixture of AcOH (20 mmol, 1.20 g), and TES (20 mmol, 2.32 g) in DMF (10 mL) was added ZnCl2 (3 mmol, 0.40 g, 0.15 equiv, dried over P2O5 under reduced pressure at r.t. for 24 h) under a nitrogen atmosphere at r.t. The reaction mixture was stirred at 120 °C for 24 h (monitored by GC). The desired triethylsilyl acetate was obtained as a colorless oil (yielding: 80%) after distillation under reduced pressure (run 1).
Triethylsilyl acetate: [5c] IR (neat): 686, 742, 883, 920, 1056, 1278, 1357, 1463, 1702, 2868, 2945 cm-1. 1H NMR (400 MHz, CDCl3): δ = 0.72 (6 H, q, J = 8.0 Hz), 0.93 (9 H, t, J = 8.0 Hz), 2.05 (3 H, s). 13C NMR (100 MHz, CDCl3): δ = 4.21, 6.30, 22.35, 171.20.

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All of the silyl esters are known compounds and were compared with authentic samples (prepared by cross-coupling of carboxylic acids and chlorosilanes in the presence of Et3N in CH2Cl2). Identification was based on their IR, 1H NMR and GCMS spectral data.