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

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.

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

References and Notes

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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.

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