Bis(trifluoromethyl)diazomethane (CAS NO.: ), which is also known as , 2-diazo-1,1,1,3,3,3-hexafluoro-, could be produced through the following synthetic routes.

A. Hexafluoroacetone hydrazone (CAS NO.: 1588-41-6). A 100-ml., three-necked, round-bottomed flask fitted with a thermometer, a gas-inlet tube, a Dewar condenser, and a magnetic stirring bar is charged with 16 g. (0.50 mole) of anhydrous hydrazine and cooled in an ice-methanol bath. The condenser is filled with a cooling mixture of ice and methanol, the magnetic stirrer is started, and 82.5 g. (0.500 mole) of hexafluoroacetone imine is slowly distilled into the flask through the gas-inlet tube, while the temperature is maintained below 10°. After the addition, which requires about 1 hour, the cooling bath is removed and the reaction mixture is allowed to warm to room temperature, then poured rapidly into a 500-ml., single-necked, round-bottomed flask containing 150 g. of phosphorus pentoxide. A spatula is used to partially mix the liquid with the phosphorus pentoxide; the flask is quickly fitted with a simple still head with condenser and heated with a heating mantle until no further distillation occurs. The crude distillate is redistilled through a 45-cm. spinning-band column, giving 48–53 g. (53–59% conversion) of hexafluoroacetone hydrazone as a colorless liquid, b.p. 95.5–96°, n25D 1.3298.

B. Bis(trifluoromethyl)diazomethane (CAS NO.: ). A 1-l., three-necked, round-bottomed flask is equipped with a sealed mechanical stirrer and a 100-ml., pressure-equalizing dropping funnel. The third neck is connected with pressure tubing to a 50-ml. capacity cold trap immersed in an acetone-dry ice cooling bath and protected from the atmosphere with a calcium chloride drying tube. The system is purged with nitrogen, and 375 ml. of benzonitrile and 120 g. (0.271 mole) of lead tetraäcetate are placed in the flask. Stirring is started and the flask is cooled with an ice bath before a solution of 45 g. (0.25 mole) of hexafluoroacetone hydrazone in 50 ml. of benzonitrile is added with the dropping funnel over a period of 1 hour. The ice bath is removed and the reaction mixture is stirred for an additional hour at room temperature. During this time some product collects in the cold trap. The remaining product is distilled into the trap at 10 mm. pressure by removing the drying tube and connecting the trap to a pump or aspirator (a small amount of acetic acid and other impurities can be removed by trap-to-trap distillation), yielding 20–21 ml. or 34–35 g. (76–79%) of bis(trifluoromethyl)diazomethane as a yellow liquid, b.p. 12–13°. The product is neither impact- nor static-sensitive and is stable to long storage at -78°; however, it partly decomposes with loss of nitrogen after several weeks at room temperature.

Notice: This procedure should be carried out in a good hood and behind a shield to avoid exposure to the toxic compounds, hexafluoroacetone imine and hydrazine.