ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

The synthesis of 2,5-lutidine and 2-ethyl-5-methylpyridine

I. Ježo, M. Karvaš, and K. Tihlárik

Slovak Academy of Sciences, Bratislava

Abstract: Dehydrobromation of Me₂CBrCH(OEt)₂, b. 162°, n20D 1.4388, d20 1.1728, gave 83% CH₂:CMeCH(OEt)₂, b. 139-40°, n20D 1.4069, d20 0.845, which gave with 1 mole Br 88% BrCH₂CBrMeCH(OEt)₂, b8 108-9°, n20D 1.4862, d20 1.502, dehydrobromated to 73% BrCH:CMeCH(OEt)₂ (I), b8 80-1°, n20D 1.4578, d20 1.263. The condensation of H₂NCMe:CHCO2Et or H₂NCEt:CHCO₂Et with I gave, resp., Et 2,5-dimethylnicotinate, 40% yield, b10 120-2° [picrate m. 147-8° (EtOH)], and Et 2-ethyl-5-methylnicotinate, 48% yield, b12 125-6°, n21.5D 1.5000 [picrate m. 117-18° (EtOH)]. Hydrolysis of the acids with concd. HCl gave, resp., 2,5-dimethylnicotinic acid-HCl, m. 240-1° (decompn.) (EtOH), and 2-ethyl-5-methylnicotinic acid-HCl, m. 223-4° (decompn.) (EtOH). Distn. with CaO gave, resp., 2,5-dimethylpyridine and 2-butyl-5-methylpyridine (II). Another synthesis of II was described. Condensation of 1-chloropenten-3-one with NaCMe(CO₂Et)₂ gave 75% EtCOCH:CHCMe(CO2Et)₂, b0.3 129-31°, n20D 1.4555, d20 1.057, which was catalytically hydrogenated to EtCOCH₂CH₂CMe(CO₂Et)₂ (III), b0.3 112°; semicarbazone-EtOH m. 122° (dil. EtOH). III oxime, b0.15, 138°, n20D 1.4583, d20 1.067, was hydrogenated with Raney Ni at 130-50°/140 atm. to form Et 2-oxo-3-methyl-6-ethylnipecotinate, yield 82%, b0.3 132-5°, d20 1.065, n20D 1.4733, After the hydrolysis, decarboxylation and redn. with LiAlH₄ gave 82% 2-ethyl-5-methylpiperidine, b. 152°, n20D 1.4432, d20 0.8362 [HCl salt m. 157-8° (EtOH); styphnate m. 203° (decompn.) (EtOH)], which was dehydrogenated with powd. Se at 300° to give II.

Full paper in Portable Document Format: 152a120.pdf (in Slovak)

Chemical Papers 15 (2) 120–130 (1961)