Synlett 2005(13): 2019-2022  
DOI: 10.1055/s-2005-872225
LETTER
© Georg Thieme Verlag Stuttgart · New York

Nickel-Catalyzed Regio- and Stereoselective Double Carboxylation of ­Trimethylsilylallene under an Atmosphere of Carbon Dioxide and Its ­Application to the Synthesis of Chaetomellic Acid A Anhydride

Masanori Takimotoa, Mitsunobu Kawamuraa, Miwako Mori*b, Yoshihiro Sato*a
a Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
Fax: +81(11)7064982; e-Mail: biyo@pharm.hokudai.ac.jp;
b Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
Fax: +81(11)7876045; e-Mail: mori@pharm.hokudai.ac.jp;
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Publikationsverlauf

Received 6 June 2005
Publikationsdatum:
20. Juli 2005 (online)

Abstract

In the presence of a nickel catalyst and excess amounts of DBU and Me2Zn, various 1-trimethylsilylallenes smoothly reacted with two equivalents of carbon dioxide at an ambient temperature and pressure in regio- and stereoselective manners to provide 1-trimethylsilylprop-1-ene-2,3-dioic acid derivatives. A short total synthesis of chaetomellic acid A anhydride was achieved using this method.

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The use of Ni(acac)2 as a catalyst precursor instead of Ni(cod)2 resulted in a slight decrease in yield of 3a.

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Typical Procedure.
To a stirred suspension of Ni(cod)2 (14 mg, 0.05 mmol) in THF (2.5 mL) was added DBU (0.37 mL, 2.5 mmol) at 0 °C. The suspension was frozen in a liquid nitrogen bath and evacuated. A balloon filled with CO2 was attached to the flask, and the frozen mixture was slowly thawed. To this suspension was added a solution of 1a (54 mg, 0.25 mmol) in degassed THF (2.5 mL) and Me2Zn (1.0 M solution in hexane, 0.75 mL, 0.75 mmol) at 0 °C. After the mixture had been stirred at ambient temperature for 3 h, 10% HCl aq was added at 0 °C, and the aqueous layer was extracted with EtOAc. The combined organic layers were washed with brine, dried over Na2SO4, and concentrated in vacuo. The residue was treated with diazomethane according to the standard procedure. The obtained crude material was purified by silica gel column chromatography to afford 3a (64 mg, 76%). IR (neat): 2951, 1739, 1723, 1602, 1216 cm-1. 1H NMR (400 MHz, CDCl3): δ = 0.15 (s, 9 H), 1.90-1.99 (m, 1 H), 2.21-2.27 (m, 1 H), 2.61 (t, J = 7.6 Hz, 2 H), 3.54 (t, J = 7.2 Hz, 1 H), 3.68 (s, 3 H), 3.74 (s, 3 H), 6.32 (s, 1 H), 7.16-7.22 (m, 3 H), 7.26-7.30 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ = -0.12, 33.24, 33.80, 49.62, 51.73, 52.11, 125.81, 128.17, 128.24, 141.00, 143.92, 145.78, 166.77, 173.15. Anal. Calcd for C18H26O4Si: C, 64.64; H, 7.83. Found: C, 64.80; H, 7.93.