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GENERAL PROCEDURE: The general procedure for the synthesis of tert-butyl 2-benzylidenehydrazinium carboxylate from tert-butyl hydrazinium carboxylate and benzaldehyde in continuous flow hydrazonium synthesis (Products 3a-j) was as follows: after the control script was started, the setup as shown in Fig. 3 was used to flush the system with methylene chloride and an aqueous extractive solvent for a few minutes until no air gaps were present in the flow path. Benzaldehyde (0.20 M) and pyridinium p-toluenesulfonate (PPTS) (0.10 M) dissolved in dichloromethane (7.5 mL) were injected into the corresponding 7.5 mL injection loop. Simultaneously, tert-butyl carbazate (0.4 M) dissolved in dichloromethane (10.0 mL) was injected into the 10.0 mL injection ring. The tert-butyl carbazate solution was injected into the system 30 seconds prior to the injection of the mixed solution of benzaldehyde and PPTS. The organic phase solution effluent from the system was collected for 40 minutes. Subsequently, the solvent was removed by distillation under reduced pressure to give the target product tert-butyl 2-benzylidenehydrazinylcarboxylate as a solid.

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