J. G. Zeevaart et al. / Tetrahedron Letters 48 (2007) 3289–3293
3293
Kondo, Y.; Inamoto, K.; Uchiyama, M.; Sakamoto, T.
Chem. Commun. 2001, 2704; (d) Beare, N. A.; Hartwig, J.
F. J. Org. Chem. 2002, 67, 541.
4d although inferior to the result achieved with the
corresponding iodo substrate. Further work is required
before a general procedure for utilising aryl bromides
can be proposed.
6. Zeevaart, J. G.; Parkinson, C. J.; de Koning, C. B.
Tetrahedron Lett. 2004, 45, 4261.
7. Xie, X.; Cai, G.; Ma, D. Org. Lett. 2005, 7, 4693.
8. (a) Klapars, A.; Huang, X.; Buchwald, S. L. J. Am. Chem.
Soc. 2002, 124, 7421; (b) Klapars, A.; Antilla, J. C.;
Huang, X.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 123,
7727.
9. (a) Beletskaya, I. P.; Cheprakov, A. V. Coordin. Chem.
Rev. 2004, 248, 2337; (b) Kiyomori, A.; Marcoux, J.-F.;
Buchwald, S. L. Tetrahedron Lett. 1999, 40, 2657; (c)
Gujadhur, R. K.; Bates, C. G.; Venkataraman, D. Org.
Lett. 2001, 3, 4315.
In conclusion, we have demonstrated the formation of
ethyl esters of 2-arylacetic acids from ethyl acetoacetate
and aryl iodides (as well as electron-deficient aryl bro-
mides) in high yield by using copper(I) catalysis in the
absence of additional ligands.11 At lower temperature,
the reaction is more selective in the conversion of ethyl
acetoacetate but results in a higher yield of the arylated
acetoacetate. Prolonged heating shifts the product distri-
bution towards the 2-arylacetic acid esters. Although
DMSO is the preferred solvent for this reaction, moder-
ate to good results were also possible in 1,4-dioxane with
the addition of ethylenediamine as ligand.
10. (a) Ma, D.; Cai, Q.; Zhang, H. Org. Lett. 2003, 5, 2453; (b)
Ma, D.; Cai, Q. Org. Lett. 2003, 5, 3799; (c) Deng, W.;
Wang, Y.; Zou, W.; Liu, L.; Guo, Q. Tetrahedron Lett.
2004, 45, 2311; (d) Deng, W.; Zou, Y.; Wang, Y. F.; Liu,
F.; Guo, Q. X. Synlett 2004, 1254; (e) Zhang, H.; Cai, Q.;
Ma, D. J. Org. Chem. 2005, 70, 5164; (f) Pan, X.; Cai, Q.;
Ma, D. Org. Lett. 2004, 6, 1809; (g) Ma, D.; Cai, Q.
Synlett 2004, 1, 128.
11. Typical experimental procedure for the CuI-catalysed
reaction between ethyl acetoacetate and an aryl halide:
A screw capped Pyrex tube (50 ml) was charged with
powdered potassium carbonate (2.1 g, 15 mmol), dry
solvent (8 ml), ethyl acetoacetate (1.3 g, 10 mmol) and
aryl halide (2 mmol). CuI (20–80 mg, 0.1–0.4 mmol, 5–
20 mol %) and naphthalene (internal standard) were
added. The tube was flushed with nitrogen, sealed and
heated to 80 ꢁC for 20 h. The amounts of ethyl acetoac-
etate, aryl halide and ethyl 2-arylacetate in the reaction
mixture were determined by GC analysis based on internal
standard calculation. Isolation was performed by dilution
with ethyl acetate (20 ml), water (10 ml) and acidification
with dilute hydrochloric acid (10% m/V). The organic
layer was diluted with hexane (40 ml) and washed with
brine (3 · 20 ml) before drying over anhydrous MgSO4
and concentration in vacuo. Column chromatography was
performed on silica gel eluting with 5–10% ethyl acetate in
hexane.
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