[Mg].C(Br)C.[CH:5]1([C:8]#[CH:9])[CH2:7][CH2:6]1.CC.[CH3:12][O:13][CH:14](OC)[O:15][CH3:16]>O1CCCC1.C1(C)C=CC=CC=1>[CH3:12][O:13][CH:14]([O:15][CH3:16])[C:9]#[C:8][CH:5]1[CH2:7][CH2:6]1
Magnesium (26.7 g, 1.1 mol) was suspended in 350 ml tetrahydrofurane and ethylbromide (74.6 ml, 1 mol) was added at such a rate, that the tetrahydrofurane continued to reflux. After completion of the addition the mixture was stirred one hour at 50-60° C. to complete the reaction. After cooling to room temperature ethynyl-cyclopropane 7 (80.6 ml, 70% in toluene, 0.95 mol) was added slowly during 30 minutes (evolution of ethane!) to the Grignard-reagent. After the addition the mixture was stirred one more hour at RT before trimethylorthoformate (120.3 ml, 1.1 mol) and toluene (400 ml) were added. The mixture was heated up (oil-bath temperature 100°-120° C.) and the tetrahydrofurane was removed by distillation during 4 hours. After cooling to RT and stirring over night the reaction mixture was diluted by addition of TBME (500 ml) and water was slowly added (50 ml). The clear organic solution was decanted from the highly viscous magnesium hydroxide phase. The magnesium hydroxide phase was extracted two more times with TBME (2 times 100 ml) and the combined organic solutions were dried over magnesium sulfate, filtered and concentrated. Compound 8 was isolated through vacuum-distillation (10 mbar, bp: 55°-60° C., 99 g, 0.7 mol).
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