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Creating structural manifolds from a common precursor: basicity gradient-driven isomerization of halopyridines

5-Chloro-2,3-difluoropyridine, an intermediate in the manufg. process of an industrial pesticide, can be hydrolyzed to 5-chloro-3-fluoro-2H-pyridinone and the latter converted into 2,5-dichloro-3-fluoropyridine, 2-bromo-5-chloro-3-fluoropyridine, 5-chloro-3-fluoro-2-iodopyridine and 3-chloro-5-fluoropyridine. Consecutive treatment of these four substrates with lithium diisopropylamide and carbon dioxide or lithium diisopropylamide and iodine affords the corresponding 4-pyridinecarboxylic acids and 4-iodopyridines, resp. Amide-promoted deprotonation of such 4-iodopyridines triggers an isomerization in which lithium and iodine change places. The resulting species can be trapped with carbon dioxide to give the acids I (X = Cl, Br, I) or neutralized to give the halopyridines II. The iodopyridines II (X = Cl, Br) can be converted into the acids III, the latter product leading also to the congeners III (X = I, H). The diiodopyridine II (X = I) provides an entry to the halopyridine II (X = H), which at the same time may act as the precursor to 3-chloro-5-fluoro-2,6-diiodo-4-pyridinecarboxylic acid, 5-chloro-3-fluoro-6-iodo-2-pyridinecarboxyic acid or 3-chloro-5-fluoro-2,6-pyridinecarboxylic acid. Finally, 5-chloro-3-fluoro-2-pyridinecarboxylic acid is accessible from either 2-bromo-5-chloro-3-fluoropyridine or 5-chloro-3-fluoro-2-iodopyridineone. [on SciFinder (R)]

    Keywords: Substitution reaction (heteroarom.; isomerization of intermediate lithiated halopyridines and derivatization to polyhalopyridines and pyridinecarboxylic acids); Carboxylation; Isomerization (isomerization of intermediate lithiated halopyridines and deri ; halopyridine isomerization; pyridine polyhalo prepn; pyridinecarboxylic acid halo prepn; reductive dehalogenation halopyridine; halogen metal exchange halopyridine

    Note:

    CAN 138:321107 27-16 Heterocyclic Compounds (One Hetero Atom) Institut de Chimie moleculaire et biologique,Ecole Polytechnique Federale,Lausanne,Switz. Journal 1434-193X written in English. 514798-04-0P; 514798-05-1P; 514798-06-2P; 514798-08-4P; 514798-09-5P; 514798-10-8P; 514798-11-9P; 514798-17-5P; 514798-19-7P; 514798-20-0P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (isomerization of intermediate lithiated halopyridines and derivatization to polyhalopyridines and pyridinecarboxylic acids); 128073-01-8P; 207994-08-9P; 514798-00-6P; 514798-01-7P; 514798-02-8P; 514798-03-9P; 514798-07-3P; 514798-12-0P; 514798-13-1P; 514798-14-2P; 514798-15-3P; 514798-16-4P; 514798-18-6P; 514798-21-1P; 514798-22-2P Role: SPN (Synthetic preparation), PREP (Preparation) (isomerization of intermediate lithiated halopyridines and derivatization to polyhalopyridines and pyridinecarboxylic acids); 514797-98-9P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. of chlorofluoroiodopyridine via halogen/metal interconversion and subsequent addn. of iodine); 514797-99-0P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. of chlorofluoropyridine via reductive dehalogenation of bromochlorofluoropyridine); 89402-43-7 Role: RCT (Reactant), RACT (Reactant or reagent) (prepn. of dichlorofluoropyridine and bromochlorofluoropyridine via hydrolysis of chlorodifluoropyridine to chlorofluoropyridinone and subsequent treatment with corresponding phosphorous trihalide); 103999-77-5P; 514797-96-7P; 514797-97-8P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. of dichlorofluoropyridine and bromochlorofluoropyridine via hydrolysis of chlorodifluoropyridine to chlorofluoropyridinone and subsequent treatment with corresponding phosphorous trihalide)

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    Record created on 2006-03-03, modified on 2016-08-08

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