In a 500ml three-necked flask, add 60ml of water and 50ml of isopropanol. Under water bath cooling, add 49.5g (0.75mol) of potassium hydroxide in portions, stirring until completely dissolved. Slowly add 39g (0.75mol) of 85% hydrazine monohydrate at <20℃ over 10 minutes. Remove the water bath and replace it with an ice bath. Add 57.5g (0.75mol) of ice-cold carbon disulfide dropwise over 100 minutes at 10℃. Stir for 2 hours after the addition is complete. Then raise the temperature to 15℃ and add 94% ice-cold carbon disulfide dropwise over 2.5 hours.
Add 5 g (0.75 mol) of dimethyl sulfate, and continue stirring for 1 hour. Filter the resulting white precipitate, wash with a small amount of ice water, vacuum dry, and recrystallize from dichloromethane to obtain 55 g of colorless flaky crystals, yield 60%, mp. 81–82 °C.
