CN1[C:7](C)(C)[CH2:6][CH2:5][CH2:4][C:3]1(C)[CH3:10].C#CCCCC.Cl[C:19]([O:21][CH2:22][CH2:23][CH2:24][CH3:25])=[O:20]>CN(C)C1C=CN=CC=1.C1C=CC([P]([Pd]([P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)([P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)[P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1.ClCCl>[C:19]([O:21][CH2:22][CH2:23][CH2:24][CH3:25])(=[O:20])[C:10]#[C:3][CH2:4][CH2:5][CH2:6][CH3:7]3.25 g (2.75 mmol) of tetrakis(triphenylphosphine)palladium(0) are introduced into 250 ml of dichloromethane in a 500 ml round-bottomed flask under argon. The dark brown solution is stirred at room temperature for 1 h. Then 150 mg (1.25 mmol) of 4-dimethylaminopyridine, 21.5 g (137.5 mmol) of 1,2,2,6,6-pentamethylpiperidine and 10.25 g (125 mmol) of 1-hexyne are added and heated to reflux at 40° C. Subsequently, 17 g (125 mmol) of n-butyl chloroformate are added dropwise over the course of 60 min. After a reaction time of 24 h, the reaction mixture is worked up by distillation to isolate n-butyl 2-heptynoate in 90% yield.
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