2-chloro-5-methylpyridin-4-amine was synthesised by reaction with 2-chloro-5-methyl-4-nitropyridine 1-oxide. The synthesis steps are as follows:
A glass pressure reactor with cross-beam stirrer was charged under argon with 29 g (153.788 mmol) of 2-chloro-5-methyl-4-nitro-1-oxidopyridin-1-ium and 2.9 g of hydrogenation catalyst (0.8% Pt and 0.6% Mo on activated carbon (D505A-105 0.8% Pt+0.6% Mo on carbon powder, BASF) and 320 ml of ethanol were added. The reactor was closed and inertized three times, each time with 3 bar argon overpressure. Hydrogenation was then carried out for 20 hours at 30℃, under a 3 bar hydrogen overpressure (conversion >98%). The reactor was inertized with argon and the reaction solution filtered through 10 g of kieselguhr. The filtrate was concentrated to dryness under reduced pressure. Yield: 23.0 g (quantitative, product still contained ethanol), purity: 97.5% (HPLC) (0051) MS (EIpos): m/z=143 [M+H]+ (0052) 1H-NMR (300 MHz, DMSO-d6): δ=1.96 (s, 3H), 6.16 (br s, 2H), 6.50 (s, 1H), 7.68 (s, 1H) In an analogous manner, a conversion of approx. 98% was achieved with a catalyst consisting of 0.8% Pt and 0.3% Mo on activated carbon. Use of 1% Pt+2% V on activated carbon achieved a conversion of approx. 87%.
