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A mixture of 5.3 g of 2-(2-pyridinyl)-6-(1H)-pyridinone and 100 ml of phosphorus oxychloride was heated on a steam bath for 18 hours and then concentrated to dryness under vacuum. Crushed ice was added to the oil residue and the mixture made basic with solid potassium carbonate. The mixture was then extracted with dichloromethane, the extracts treated with activated carbon, filtered and concentrated, giving a solid which was purified by chromatography on silica gel with ethyl acetate as solvent, giving 4.1 g of 6'-chloro-2,2'-bipyridine as white crystals, mp 60-62 C.
To 100 ml of phosphorus oxychloride, cooled in an ice bath, was added 5.3 g of [2,2'-bipyridin]-6(1H)-one. The mixture was warmed to room temperature and then heated on a steam bath for 18 hours, then concentrated under vacuum. Crushed ice was added to the residual oil and the solution was basified with solid potassium carbonate. This mixture was extracted with methylene chloride, the extract was dried and evaporated in vacuo to a solid This solid was dissolved in ethyl acetate and placed on a silica gel column. The column was eluted with ethyl acetate and the obtained solid recrystallized from heptane, giving 6'-chloro-2,2'-bipyridine as white crystals, mp 60-62 C., which was then treated as described in Example 1, giving the desired product.