Benzaldehyde → Piperazine
Reaktionsgleichung
[Zn:1].C[Si](C)(C)[Cl:4].C(=O)C1C=CC=CC=1.[Br:15]CC(OC)=O.C(Cl)(=O)C.[NH:25]1[CH2:30][CH2:29][NH:28][CH2:27][CH2:26]1>O1CCCC1>[Cl-:4].[Br-:15].[Zn+2:1].[NH:25]1[CH2:30][CH2:29][NH:28][CH2:27][CH2:26]1[Zn:1].C[Si](C)(C)[Cl:4].C(=O)C1C=CC=CC=1.[Br:15]CC(OC)=O.C(Cl)(=O)C.[NH:25]1[CH2:30][CH2:29][NH:28][CH2:27][CH2:26]1>O1CCCC1>[Cl-:4].[Br-:15].[Zn+2:1].[NH:25]1[CH2:30][CH2:29][NH:28][CH2:27][CH2:26]1
At room temperature, a three-neck flask equipped with a reflux condenser, internal thermometer, dropping funnel and stirrer under protective nitrogen gas was initially charged with 4.6 g of zinc powder (71 mmol) in 40 ml of tetrahydrofuran. After 0.8 ml of trimethylchlorosilane had been added, the mixture was heated to 50° C. for 15 min, and 6.5 g of benzaldehyde (57 mmol) were added undiluted. 10.4 g of methyl bromoacetate (68 mmol) were subsequently added dropwise at 45° C. within 5 min while maintaining the temperature at 50° C. by external cooling. The mixture was then stirred at 50° C. for 10 min (formation of the zinc alkoxide). After cooling to 10° C, 5.3 g of acetyl chloride (68 mmol) were added and the mixture was heated at 40° C. for 30 min. At 20° C., 7.4 g of piperazine (85 mmol) were subsequently added as solid. The mixture was then stirred at 50° C. for 3 h. After the tetrahydrofuran solvent had been virtually completely distilled off (recovery of the anhydrous solvent), 40 ml of pentane were added, the suspension was cooled to −20° C., stirred for 1 h and solid formed (complex of zinc bromide chloride and piperazine) was filtered off. The solid was washed three times with 10 ml of cold pentane each time. Pentane was distilled off under reduced pressure (recovery of pentane) and the desired product methyl 3-acetoxy-3-phenylpropionate was obtained in a yield of 11.3 g (89% of theory) and a purity of >95% (HPLC). The zinc content of the product is 20 ppm (ICP).
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