| 摘要 |
Disclosed are preferred processes for the preparation of 2-halo-nicotinic acid derivatives of formula (IV): <IMAGE> (IV) by cyclocondensation of a 4-halo-4-cyanocarbonyl compound of formula (III): <IMAGE> (III) wherein X is Cl or Br; Y is a carbonyl group and R1, R2 and R3 are each, independently, H, Cl, Br or an organic radical. Further preferred aspects include the preparation of the above-noted 4-halo-4-cyanocarbonyl compound via Michael addition of a 2-halonitrile with an alpha , beta -unsaturated aldehyde or ketone, and the preparation of the 2-halonitrile by redistribution of halogen between a 2,2-dihalonitrile and a parent nitrile.
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