[3252-43-5]  · C2HBr2N  · Dibromoacetonitrile  · (MW 198.84)

(reagent used to introduce an a-bromo acid1 or ester moiety1,2 directly on a substrate having a carbonyl group; can be also used for heterocyclic syntheses;8,10 and other miscellaneous reactions18,19)

Physical Data: bp 68-69 °C/24 mmHg; d 2.296 g cm-3; nD20 1.5390.

Solubility: insol H2O; sol ether, alcohol, THF.

Form Supplied in: colorless liquid.

Handling, Storage, and Precautions: dibromoacetonitrile is reputed to be relatively toxic, lachrymatory, and light sensitive. Usual precautions of storage in darkness between 0-5 °C and handling in a fume hood are recommended.

Homologation of Carbonyl Groups into a-Bromo Acids or Esters.

Divergent pathways have been described in the Darzens reaction of aldehydes or ketones with Dichloroacetonitrile3 and dibromoacetonitrile1 in a basic alcoholic medium. Whereas a-chlorinated glycidic imino ethers are obtained in the reaction with dichloroacetonitrile, a-bromo acids or a-bromo esters are the products of the Darzens reaction with dibromoacetonitrile. The reaction is carried out in one pot and leads to a-bromo acids or esters in rather good yields (eq 1).1,2 The reaction combined with a subsequent substitution of the bromine by ammonia4,5 or by potassium phthalimide6 on the a-bromo carbonyl compound holds important synthetic potential for the conversion of a carbonyl group into an a-amino acid.

Heterocycle Syntheses.

Very few methods exist for the introduction of halogen at the 2- and 3-positions of the pyridine ring.7 It was reported that dibromoacetonitrile adds smoothly under mild conditions to methacrolein, in the presence of a catalytic amount of Copper(I) Chloride and Tri-n-butylphosphine as co-catalysts, to afford an adduct that readily cyclizes to give 2,3-dibromo-5-methylpyridine. No trace of the primary adduct was detected in the isolated product (eq 2). Under the same reaction conditions, dichloroacetonitrile leads to a mixture of 2,3-dichloro-5-methylpyridine and 2,4-dichloro-4-methyl-5-oxopentanenitrile.8

Special emphasis has also been given to the development of synthetic procedures for the preparation of polyhalogenation products from trialkyl-1,3,5-triazines.9 Dibromoacetonitrile trimerizes in the presence of Aluminum Bromide in acidic medium and yields tris(dibromomethyl)-1,3,5-triazine (eq 3),10 which constitutes the precursor of a synthetic equivalent of the unstable triformyl-1,3,5-triazine (eq 4) not previously isolated.11,12 The alternative, classical method for the synthesis of tris(dibromomethyl)-1,3,5-triazine requires the availability of the trimethyl-1,3,5-triazine as starting material.9

Miscellaneous Reactions.

Addition of HCN to nitriles having hydrogen atoms on the a-carbon atom occurs in only a few special cases.13-15 For the addition to be successful, the cyano group has to be activated by one or more strongly electron-withdrawing groups on the a-carbon.16,17 A selected example reports that dichloro- and dibromoacetonitrile react with HCN to give b,b-dihalo-a-aminoacrylonitriles, a new class of acrylonitrile compounds, in good yields (eq 5).18

In certain reactions dibromoacetonitrile reacts as the bromocyanomethyl radical. For instance, CHBr2CN was used to prepare several 1-cyano-2-(trichloroethyl)cyclopropanes of importance in pyrethroid chemistry.19 The sequence of reactions involves homolytic displacement of cobaloxime(II) from an allylcobaloxime(II) complex by the bromocyanomethyl radical (bis(dimethylglyoximato)pyridine = (dmgH)2py). The bromocyanomethyl radical attacks regiospecifically at the g-carbon of the allyl ligand to afford the 2-bromo-4-phenylpent-4-enenitrile (eq 6).20 Subsequent treatment with the ((dmgH)2py)cobaltate(II) ion in aqueous methanol at ambient temperature (eq 7) and then with trichloromethanesulfonyl chloride leads to the corresponding 1-cyano-2-(trichloroethyl)cyclopropane (eq 8).19

Related Reagents.

Dichloroacetonitrile; Ethyl Dibromoacetate.

1. Coutrot, P.; Legris, C.; Villieras, J. BSF(2) 1974, 1971.
2. Legris, C.; Coutrot, P.; Villieras, J. CR(C) 1974, 278, 77.
3. Coutrot, P. BSF(2) 1974, 1965.
4. Carter, H. E.; West, H. D. OS 1940, 20, 101.
5. Marvel, C. S. OS 1941, 21, 60.
6. Sheehan, J. C.; Bolhofer, W. A. JACS 1950, 72, 2786.
7. Pyridine and its Derivatives; Abramovitch, R. A., Ed.; Wiley: New York, 1974; Part II p 407.
8. Pews, R. G.; Lysenko, Z. JOC 1985, 50, 5115.
9. Schaefer, F. C.; Ross, J. H. JOC 1964, 29, 1527.
10. Sumera, F.; Le Rouzic, A.; Raphalen, D.; Kerfanto, M. JHC 1987, 24, 793.
11. Schaefer, F. C. JOC 1962, 27, 3608.
12. Grundmann, C.; Mini, V. JOC 1964, 29, 678.
13. Von Hellmut, B. H.; Schmötzer, G.; Oehler, E. LA 1956, 600, 81.
14. Ferris, J. P.; Orgel, L. E. JACS 1965, 87, 4976; 1966, 88, 3829.
15. Atkinson, M.; Horsington, A. M. JCS(C) 1969, 2186.
16. Middleton, W. J.; Krespan, C. G. JOC 1968, 33, 3625.
17. Begland, R. W.; Cairncross, A.; Donald, D. S.; Hartter, D. R.; Sheppard, W. A.; Webster, O. W. JACS 1971, 9, 4953.
18. Matsumura, K.; Saraie, T.; Hashimoto, N. CC 1972, 705.
19. Bury, A.; Corker, S. T.; Johnson, M. D. JCS(P1) 1982, 3, 645.
20. Bury, A.; Cooksey, C. J.; Funabiki, T.; Gupta, B. D.; Johnson, M. D. JCS(P2) 1979, 8, 1050.

Philippe Coutrot & Claude Grison

Nancy I University, France

Jean Villieras

Nantes University, France

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