ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
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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)

Tuesday, June 25, 2024

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