[75-61-6]  · CBr2F2  · Dibromodifluoromethane  · (MW 209.82)

(fluorinating reagent; can function as a precursor for the introduction of CF2Br, CF3, and =CF2 groups into organic compounds)

Physical Data: bp 22.78 °C.1

Solubility: sol ether, acetone, alcohol, benzene.

Form Supplied in: colorless liquid.

Preparative Methods: dibromodifluoromethane is prepared by the reaction of CFBr3 with AgF (50-60%),2 by the reaction of CBr4 with SbBr2F3 (80%),3 or by the reaction of CBrF2CO2Ag with Br2 (81%).4 Industrially, gas-phase reactions are employed to prepare CF2Br2. For example, CF2Br2 is formed from the reaction of CF2H2 and Br2 at 500 °C,5 the reaction of CF2BrCl and HBr at 600 °C,6 and the reaction of ClCF2C(O)CF2Cl and Br2 at 580-650 °C.7

Handling, Storage, and Precautions: use in a fume hood.

Addition to Alkenes and Alkynes.

Radical addition of CF2Br2 to alkenes and alkynes is initiated by irradiation,8 metals,9 boranes,10 and peroxide11 to give the corresponding adducts (eq 1). Reaction of CF2Br2 with an enamine (without any initiator) followed by hydrolysis produces a-bromodifluoromethylated ketones.12

Reactions with Nucleophiles.

Treatment of carbanions, such as [(EtO2C)2CR]-,13 RC&tbond;C-,14 and [PhCH=NC(Me)CO2Me]-15 with CF2Br2 gives the corresponding bromodifluoromethylated compounds. Reaction of CF2Br2 with phosphines or phosphites affords high yields of bromodifluoromethylphosphonium salts and bromodifluoromethylphosphonates, respectively (eqs 2 and 3).16 CF2Br2 also reacts with sulfur and oxygen nucleophiles to produce bromodifluoromethyl sulfides17 and ethers,18 respectively. Reaction of pyrazole with CF2Br2 and NaH yields N1-bromodifluoromethylpyrazole.19


CF2Br2 is a precursor in the Wittig reaction for the introduction of the =CF2 moiety into organic molecules. In the presence of CF2Br2 and Hexamethylphosphorous Triamide or Triphenylphosphine, aldehydes and ketones can be converted to the corresponding 1,1-difluoroalkenes (eq 4).20 Alternatively, in the presence of phosphines or metals (Zinc or Cd), treatment of the phosphonium salt [R3PCF2Br]+ Br- with aldehydes and ketones also gives the corresponding 1,1-difluoroalkenes.21

Formation and Reactions of CF3Cu.

CF3Cu is readily prepared from CF2Br2. Treatment of CF2Br2 and Zn or Cd in DMF forms CF3ZnX or CF3CdX.22 Metathesis of the CF3ZnX or CF3CdX with CuX gives the CF3Cu reagent,23 which couples with aryl and vinyl iodides, allyl chloride,23 and activated aryl chlorides (eq 5 and 6).24

Formation and Reactions of Difluorocarbene.

CF2Br2 is a precursor of difluorocarbene. In the presence of Zn or Lithium Aluminum Hydride-Titanium(IV) Chloride, reaction of CF2Br2 with alkenes gives 1,1-difluorocyclopropane derivatives (eq 7);25 difluorocarbene has been proposed as the active intermediate in the reaction. Alternatively, difluorocarbene has been generated from [Ph3PCF2Br]+ Br- and fluoride ion, which is prepared from the reaction of CF2Br2 and triphenylphosphine (eq 8).26 More conveniently, difluorocarbene has also been generated from CF2Br2, a tertiary phosphine, and fluoride ion.26a Treatment of aldehydes or ketones with the CF2Br2/Zn reagent gives gem-difluoroalkanes.27

1. Kudchadker, A. P.; Kudchadker, S. A.; Shukla, R. P.; Patnaik, P. R. J. Phys. Chem. Ref. Data 1979, 8, 499.
2. Rathsburg, H. CB 1918, 51, 669.
3. Rzepczynski, W. Pol. Patent 1970, 60 068 (CA 1971, 74, 41 877).
4. Haszeldine, R. N. JCS 1952, 4259.
5. Dow Chem. Co. U.S. Patent 1953, 2 639 300 (CA 1954, 48, 3382f).
6. Du Pont Co. U.S. Patent 1956, 2 729 687 (CA 1956, 50, 11 360i).
7. Allied Chem. Co. U.S. Patent 1959, 2 885 450 (CA 1959, 53, 16 961d).
8. (a) Tarrant, P.; Stump, E. C., Jr. JOC 1964, 29, 1198. (b) Molines, H.; Wakselman, C. JFC 1987, 37, 183.
9. (a) Burton, D. J.; Kehoe, L. J. TL 1966, 5163. (b) Elsheimer, S.; Michael, M.; Landavazo, A.; Slattery, D.; Weeks, J. JOC 1988, 53, 6151. (c) Nohair, K.; Lachaise, I.; Paugam, J.-P.; Nedelec, J.-Y. TL 1992, 33, 213. (d) Hu. C.-M.; Chen, J. CC 1993, 72.
10. Sugimoto, J.; Miura, K.; Oshima, K.; Utimoto, K. CL 1991, 1319.
11. (a) Tarrant, P.; Lovelace, A. M. JACS 1954, 76, 3466. (b) Durrell, W.; Lovelace, A. M.; Adamczak, R. L. JOC 1960, 25, 1661.
12. Rico, I.; Cantacuzene, D.; Wakselman, C. TL 1981, 3405.
13. Everett, T. S.; Purrington, S. T.; Bumgardner, C. L. JOC 1984, 49, 3702.
14. Rico, I.; Cantacuzene, D.; Wakselman, C. JCS(P1) 1982, 1063.
15. Bey, P.; Vevert, J. P. TL 1978, 1215.
16. (a) Naae, D. G.; Kesling, H. S.; Burton, D. J. TL 1975, 3789. (b) Burton, D. J.; Flynn, R. M. JFC 1977, 10, 329.
17. (a) Rico, I.; Wakselman, C. T 1981, 37, 4209. (b) Burton, D. J.; Wiemers, D. M. JFC 1981, 18, 573. (c) Suda, M.; Hino, C. TL 1981, 1997.
18. (a) Rico, I.; Wakselman, C. TL 1981, 22, 323. (b) Li, X.; Pan, H.; Xi Kui, J. TL 1984, 25, 4937.
19. Morimoto, K.; Makino, K.; Yamamoto, S.; Sakata, G. JHC 1990, 27, 807.
20. (a) Naae, D. G.; Burton, D. J. JFC 1971, 1, 123. (b) Naae, D. G.; Burton, D. J. SC 1973, 3, 197. (c) Damon, D. B.; Hoover, D. J. JACS 1990, 112, 6439.
21. (a) Hayashi, S.-I.; Nakai, T.; Ishikawa, N.; Burton, D. J.; Naae, D. G.; Kesling, H. S. CL 1979, 983. (b) Burton, D. J.; Kesling, H. S.; Naae, D. G. JFC 1981, 18, 293.
22. Burton, D. J.; Wiemers, D. M. JACS 1985, 107, 5014.
23. Wiemers, D. M.; Burton, D. J. JACS 1986, 108, 832.
24. Clark, J. H.; Denness, J. E.; McClinton, M. A.; Wynd, A. J. JFC 1990, 50, 411.
25. (a) Dolbier, W. R., Jr.; Wojtowicz, H.; Burkholder, C. R. JOC 1990, 55, 5420. (b) Dolbier, W. R., Jr.; Burkholder, C. R. JOC 1990, 55, 589.
26. (a) Burton, D. J.; Naae, D. G. JACS 1973, 95, 8467. (b) Bessard, Y.; Schlosser, M. T 1991, 47, 7323.
27. Hu, C.-M.; Qing, F.-L.; Shen, C.-X. JCS(P1) 1993, 335.

Donald J. Burton & Weiming Qui

University of Iowa, Iowa City, IA, USA

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