Benzaldehyde (1.04 mL, 10 mmol) was slowly added dropwise to a solution of hydrazine hydrate (2.5 mL, 30 mmol) in ethanol (10 mL) under nitrogen protection for a controlled time of 10 minutes. The reaction mixture was stirred continuously for 1.5 h at room temperature. Upon completion of the reaction, an appropriate amount of water was added and the ethanol was subsequently removed by distillation under reduced pressure. The aqueous phase was extracted with dichloromethane (DCM, 4 times). The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford (phenylmethylene) hydrazine as a yellow oil (Product 2, 1.2 g, quantitative yield). Mass spectrometry (MS) analysis showed [MH]+ m/z 121.1.
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