Diglyme → 2-Butylcyclopropane-1-carboxylic acid

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A solution of triethylphosphonoacetate (22.4 g, 0.1 mol) in 13 mL of diglyme is added to a mixture of 13 mL of diglyme and sodium hydride (60%, 5.7 g, 0.12 mol) in mineral oil. When hydrogen evolution ceased, 1,2-epoxyhexane (12 g, 0.12 mol) in diglyme (12 mL) is added. The mixture is stirred for 1 day at 25 degrees C. and 3 hours at 140 degrees C. A mixture of sodium hydroxide (15 g in 25 mL of water) is added in the cold. The mixture is refluxed 15 hours, diluted with cold water (100 mL), and washed with ether (3×50 mL). Acidification to pH=2 with sulfuric acid (25%), extraction with ether (5×25 mL), drying the ether over anhydrous sodium sulfate, filtration and concentration gives 2-butylcyclopropanecarboxylic acid. The acid (5.0 g, 0.035 mmol) in dichloromethane (15 mL) is heated with thionyl chloride (5.1 g, 3.1 mL) for 15 hours at 60 degrees C. The reaction mixture is distilled (76 degrees C.-80 degrees C.) to give the acid chloride which is dissolved in acetone (15 mL), cooled to −10 degrees C. and treated with sodium azide (2.2 g, 33.8 mmol) in water (5 mL). The reaction mixture is stirred at −10 degrees C. for another 1 hour and then poured onto ice/water, extracted with ether (3×10 mL), dried, and cautiously evaporated to dryness at 20-25 degrees C. under reduced pressure. The residue is dissolved in toluene (15 mL) and carefully warmed to 100 degrees C. while vigorously stirring for 1 hour. Concentrated hydrochloric acid (7 mL) is added and the reaction mixture is refluxed for 15 minutes. The acidic layer is evaporated to dryness to give the title compound, MH+=114.2.

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