Phosphorus oxychloride → Pyrazine, 2-chloro-3-ethyl-

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Reaction Steps

3-Ethyl-2-hydroxypyrazine (5 g) was heated with phosphorus oxychloride (15 ml) at reflux for 3 hours. The reaction was allowed to cool to ambient temperature and then poured onto 200 g of crushed ice. The mixture was extracted with dichloromethane (3×150 ml) and the combined extracts were dried (MgSO4). Volatile material was removed by evaporation to give a brown oil. The oil was purified by chromatography on silica gel, eluting with dichloromethane, to give 2-chloro-3-ethylpyrazine as a colourless oil (5.64 g, 98%); 1H NMR (d6 -DMSO, 200 MHz): 1.25 (t,3H), 2.93 (q,2H), 8.36 (d,1H), 8.59 (d,1H); mass spectrum (+ve CI): 143 (M+H)+.

Provenance & Evidence