Indium-Mediated Addition of 4-Bromocrotonic Acid to Aldehydes and Ketones
137
available materials. Our approach is highly regioselective
facilitating the generation of only the α-adduct, and is tolerant
of a range of solvents and reaction conditions.
quota studentship and travel award, and a MacRobertson
Scholarship.
References
Experimental
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General Procedure for the Allylation of Carbonyl Compounds
using Indium
4-Bromocrotonic acid (0.198 g, 1.2 mmol) and indium powder (Aldrich,
99.99% 100 mesh; 0.114 g, 1.0 mmol) were added to 2.5 mL of solvent
(see Table 1) and stirred for a few minutes. The carbonyl compound
(1 mmol) was then added, and the reaction vessel stoppered and the
reaction mixture stirred at 30◦C or 50◦C for 16 h or 72 h. At the end of
the reaction different methods were employed for the workup, as listed
below.
(b) R. Hamasaki, Y. Chounan, H. Horino, Y. Yamamoto,
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Methanol: Remaining indium and indium hydroxide was removed
by filtration through a cotton wool/kieselguhr plug, then the solvent was
removed in vacuo.
Water: The products were extracted with diethyl ether (5 × 5 mL),
the extracts were combined and dried (MgSO4), then the solvent was
removed in vacuo.
[bmIm][BF4]: At the end of the reaction, the mixture was quenched
with deionized water (3 mL). The water/ionic liquid mixture was then
extracted with diethyl ether (5 × 5 mL), the extracts were combined and
dried (MgSO4), then the solvent was removed in vacuo.
Ethanol/water (20%): The products were extracted with diethyl
ether (5 × 5 mL), the extracts were combined and dried (MgSO4), then
the solvent was removed in vacuo.
Tetrahydrofuran: At the end of the reaction, the mixture was
quenched with deionized water (3 mL). The products were extracted
with diethyl ether (5 × 5 mL), the extracts were combined and dried
(MgSO4), then the solvent was removed in vacuo.
Soc., Perkin Trans.
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(00)01676-2
Products were purified by flash chromatography (ethyl acetate/
hexanes).
[6] C. M. Gordon, A. McCluskey, unpublished results.
[7] (a) X.-R. Li, T.-P. Loh, Tetrahedron Asym. 1996, 7, 1535.
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Representative Characterization Data
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Tetrahedron Lett. 2000, 41, 6511. doi:10.1016/S0040-
4039(00)01040-6
2-(Hydroxyphenylmethyl)-but-3-enoicacid:Yield44–87%. δH (CDCl3)
8.12 (1H, s, COOH), 5.94–5.88 (1H, q, CH(COOH)CHCH2), 5.29–
5.13 (2H, dd, J 10.2, 17.2, CHCH2), 5.08–5.06 (1H, d, J 5.6,
PhCH(OH)CH), 4.60–4.10 (1H, br, CH(OH)CH), 3.38–3.33 (1H, dd,
J 5.6 Hz, CH(OH)CH(COOH)). δC (CDCl3) 177.0, 140.3, 130.9, 128.4,
128.0, 126.4, 121.3, 73.7, 57.7.
[8] A. McCluskey, I. W. Muderawan, Muntari, D. J. Young, Synlett
1998, 909. doi:10.1055/S-1998-1807
Acknowledgements
This work received financial support from the University
of Newcastle. C.R. acknowledges the receipt of an EPSRC