2,6-Dibromopyridine

Description

2,6-Dibromopyridine is a halogenated pyridine compound used as a pharmaceutical intermediate in the synthesis of the migraine drug (Lasmiditan).Lasmiditan is an oral prescription drug used to treat acute migraine headaches with or without aura. It is important to note that it is not used for migraine prevention.

Chemical Properties

White to light yellow crystalline powder

Uses

2,6-Dibromopyridine is used as a tridentate chelating ligand and in the formation of macrocycles containing the terpyridine moiety. It is also used to produce 6-bromo-2-methoxypyridine.

Application

2,6-Dibromopyridine is an important organic chemical reagent with a wide range of uses:
(1) Spectroscopic studies: There is a satisfactory correlation between the normal Raman spectra of 2,6-dibromopyridine in aqueous solution and the surface enhanced Raman (SER) spectra in silver-pure sols. In the SER spectra, the compounds are notable for the stretching of the vibrational modes of (py)CBr and (CC,CN)(py) in 2,6-dibromopyridine to give enhanced vibrational intensities at 1175 and 1369 cm-1 , respectively^[1].
(2) Reaction reagent: Friedel–Crafts-type acylation of alkenes with acyl chlorides has been successfully conducted with a wide substrate scope by the combined use of AlCl3 and 2,6-dibromopyridine. Trisubstituted alkenes afford allylketones or vinylketones depending on the presence or absence of hydrogen atom(s) at the β-position to the acylation site, while monosubstituted alkenes exclusively afford vinylketones^[2]. In addition, 2,6-Dibromopyridine can be brominated to form 2,4,6-tribromopyridine by reacting with a mixture of bromine at 450~ 550 °C^[3]. It can also be lithiated with butyl lithium for the synthesis of L-739,010^[4].
(3) A selective palladium-catalysed arylation of 2,6-dibromopyridine has been developed by employing N-heterocyclic carbene ligands. Selective mono-arylation was performed in water/acetonitrile solvent system at ambient temperature with catalyst loading of 0.1 mol%. This reaction was also found to proceed smoothly in water although at a slightly elevated temperature of 80 °C. 2,6-Disubstituted and diversely substituted 2,6-pyridines were also obtained in high yields which will be of importance to organic and medicinal chemists^[5].

Purification Methods

Purify 2,6-dibromopyridine by steam distillation, then recrystallise it twice from EtOH. It does not form an HgCl2 salt. [den Hertog & Wibaut Recl Trav Chim Pays Bas 51 381 1932, Beilstein 20/5 V 435.]

References

[1] S. CHATTOPADHYAY S. K B. Surface-enhanced Raman spectroscopy of 2,5-dibromopyridine and 2,6-dibromopyridine[J]. Spectrochimica acta. Part A: Molecular spectroscopy, 1992. DOI:10.1016/0584-8539(92)80253-S.
[2] SHINYA TANAKA*. Acylation of Alkenes with the Aid of AlCl3 and 2,6-Dibromopyridine[J]. Organic Letters, 2019. DOI:10.1021/acs.orglett.9b02688.
[3] H. J. HERTOG C. R K ;W Combe. Substitution reactions in the pyridine nucleus at elevated temperatures (I). The bromination of 2,6‐dibromopyridine[J]. Recueil des Travaux Chimiques des Pays-Bas, 2010. DOI:10.1002/RECL.19580770109.
[4] D. CAI T. V D Hughes. A study of the lithiation of 2,6-dibromopyridine with butyllithium, and its application to synthesis of L-739,010[J]. Tetrahedron Letters, 1996. DOI:10.1016/0040-4039(96)00336-X.
[5] PRAJAPATI D, SCHULZKE C, KINDERMANN M K, et al. Selective palladium-catalysed arylation of 2,6-dibromopyridine using N-heterocyclic carbene ligands[J]. RSC Advances, 2015. DOI:10.1039/C5RA10561G.