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Synlett 2011(14): 2039-2042  
DOI: 10.1055/s-0030-1261173
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Me3Ga-Mediated Addition of Acetylenes to α-Keto Esters: A New Method for the Synthesis of α-Hydroxy Esters

Honglai Jianga, Aijun Lina, Hao Penga, Yuhua Zhua, Yi Pana, Chengjian Zhu*a,b, Yixiang Cheng*a
a School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, P. R. of China
Fax: +86(25)83594886; e-Mail: cjzhu@nju.edu.cn;
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. of China
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Publication History

Received 24 April 2011
Publication Date:
10 August 2011 (online)

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Abstract

Trimethylgallium reagent was found to promote the addition of acetylenes to various α-keto esters. This reaction was efficiently carried out in anhydrous hexane at room temperature under mild conditions, and the corresponding α-hydroxy esters were obtained in good to excellent yields.

Key words

trimethylgallium - alkynylation - α-keto ester - α-hydroxy ester - acetylene

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General Experimental Procedure
In a 20 mL Schlenk reaction tube, 1 M solution of Me3Ga (0.15 mL, 0.15 mmol, 1 M in toluene) and 4-methoxy-phenylacetylene (20 mg, 0.15 mmol) were dissolved in anhyd hexane (1 mL) and stirred for 1 h at r.t. under an nitrogen atmosphere. Then the mixture was cooled to 0 ˚C and methyl benzoylformate (0.1 mmol) was added, and stirred at r.t. for indicated time in Table  [²] , then sat. NH4Cl (1 mL) was added to quench the reaction. The aqueous layer was separated and further extracted with EtOAc, the organic layers were combined and dried. Evaporation of the solvent gave the crude product, which was further purified by preparative TLC (PE-EtOAc = 10:1) to give corresponding α-hydroxy esters.