To a stirred suspension of anhydrous MgSO4 in dichloromethane (25 mL) was sequentially added paraformaldehyde (0.56 g, 18.7 mmol) and freshly distilled n-propylamine (18.7 mmol). The reaction mixture was stirred at room temperature. Upon completion of the reaction, the MgSO4 was removed by filtration and the filtrate was concentrated in vacuum to afford the crude product of 1,3,5-tripropyl-1,3,5-triazacyclohexane, which could be used in the subsequent steps without further purification.
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