Acetic Acid → Dimethyl (3,3-dimethyl-2-oxohept-5-yn-1-yl)phosphonate

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Reaction Conditions

Reaction Steps

Under argon atmosphere, a solution of n-butyl lithium in hexane (33 ml, 0.054 mol, 1.04N) was added dropwise with stirring into a solution of dimethyl methylphosphonate (6.82 g, 0.055 mol) in anhydrous THF (100 ml) at -78° C. and the mixture was stirred for 30 min. at -78° C. To the mixture was added dropwise a solution of ethyl 2,2-dimethyl-4-hexynoate (3.7 g, 0.022 mol) in anhydrous THF (15 ml) and the mixture was stirred for 30 min. at -78° C. and then for one hour at room temperature. To the resulting mixture were added acetic acid (3.1 ml, 0.054 mol) and water (10 ml), and the mixture was then concentrated. The residue was diluted with water (20 ml) and extracted with ethyl acetate (100 ml×2). The combined ethyl acetate layers were washed with water (20 ml) and with brine (20 ml), dried over anhydrous sodium sulfate, and concentrated. Distillation of the residue in vacuo gave dimethyl 3,3-dimethyl-2-oxo-5-heptynylphosphonate (5.04 g, 0.020 mol, 93%, B.p.: 108°-110° C./0.15 mmHg). The product was assigned the structure by the following data.

Provenance & Evidence