Organic Syntheses, Coll. Vol. 6, p.161 (1988); Vol. 50, p.6 (1970).
Caution! This procedure should be carried out in a good hood and behind a shield to avoid exposure to the toxic compounds, hexafluoroacetone imine
A. Hexafluoroacetone hydrazone
. 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
[Org. Synth., Coll. Vol. 6, 10 (1988)
] 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) (Note 1) of hexafluoroacetone imine
[Org. Synth., Coll. Vol. 6, 664 (1988)
] 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 (Note 2)
; the flask is quickly fitted with a simple still head with condenser and heated with a heating mantle until no further distillation occurs (Note 3)
. The crude distillate is redistilled through a 45-cm. spinning-band column
, giving 48–53 g.
conversion) of hexafluoroacetone hydrazone
as a colorless liquid, b.p. 95.5–96°
. 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 (Note 4)
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.
) (Note 5)
as a yellow liquid, b.p. 12–13°
. The product is neither impact- nor static-sensitive (Note 6)
and is stable to long storage at −78°; however, it partly decomposes with loss of nitrogen
after several weeks at room temperature.
If it is inconvenient to distill the hexafluoroacetone imine
directly from a cylinder, it may be condensed first in a calibrated cold trap cooled to −10°, then distilled from the trap into the reaction mixture. About 55 ml. of the imine, measured at −10°, corresponds to 0.5 mole.
Caution! A spontaneous reaction may result if mixing is prolonged beyond 1 minute. Rubber gloves should be worn to avoid exposure to hydrazine vapors.
About 14 g.
) of hexafluoroacetone imine
can be recovered during the redistillation step if the receivers for both distillations are cooled to −10° or lower. The yield of the hydrazone is about 67%
if the recovered imine is taken into account.
The submitters have obtained yields as high as 90%
on runs two times this scale.
Caution! Toxicity data on this material are not available; therefore, it should be assumed to be as toxic as other diazo compounds and handled only in an efficient hood. Although it has been stored in stainless-steel cylinders at autogenous pressure and handled without incident, contact with reagents likely to initiate rapid evolution of nitrogen should be carried out with caution.
is a reactive, electrophilic compound, in that it forms adducts with nucleophiles such as amines and phosphines3
and adds to olefins, acetylenes,3
and thiocarbonyl compounds, forming heterocycles. It has been used as a source of bis(trifluoromethyl)carbene
in reactions with benzene
saturated hydrocarbons,4 carbon disulfide
and transition metal compounds,6
and it undergoes a unique radical chain reaction with saturated hydrocarbons, giving hydrazone and azine adducts.4
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
acetic acid (64-19-7)
carbon disulfide (75-15-0)
Propane, 2-diazo-1,1,1,3,3,3-hexafluoro- (684-23-1)
Hexafluoroacetone imine (1645-75-6)
Hexafluoroacetone hydrazone (1588-41-6)
phosphorus pentoxide (1314-56-3)
lead tetraacetate (546-67-8)
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