Cl[C:2]1[C:3]([C:9]#[N:10])=[N:4][C:5]([Cl:8])=[CH:6][CH:7]=1.CS(C)=O.[CH2:15]([SH:17])[CH3:16].CC([O-])(C)C.[K+]>C1COCC1>[Cl:8][C:5]1[N:4]=[C:3]([C:9]#[N:10])[C:2]([S:17][CH2:15][CH3:16])=[CH:7][CH:6]=1
In a reaction flask with condenser, mechanical stirrer, thermometer and dropping funnel were placed 53.4 g of 3,6-dichloro-2-pyridinecarbonitrile and 300 ml of DMSO. The mixture was chilled to about 10°-15° C. and then 19.8 g of ethanethiol was added. While maintaining the temperature at <20° C., 34.8 g of t-BuOK in 300 ml of THF was added in small portions. After the addition was complete, the reaction mixture was warmed to 20° C. and stirred for about 40 hrs. The reaction mixture was then poured onto about 2 kilograms (kg) of ice, stirred and filtered leaving a solid residue. The residue was washed with water, dissolved in CH2Cl2, dried over MgSO4, concentrated and diluted with hexane to give 19.0 g of 6-chloro-3-ethylthio-2-pyridinecarbonitrile. The filtrate was concentrated and separated on a Water's Prep LC 500 instrument using 15% ethyl acetate in hexane to give another 10.1 g of the same isomer. Total yield of 6-chloro-3-ethylthio-2-pyridinecarbonitrile was 29.1 g (46.5%), m.p. 79°-81° C. Further separation on the Prep LC 500 instrument gave a small amount of 3-chloro-6-ethylthio-2-pyridinecarbonitrile (m.p. 46°-48° C.) and 3,6-bis-ethylthio-2-pyridinecarbonitrile (m.p. 63°-64° C.).
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