Strategies for the selective functionalization of dichloropyridines at various sites

Whereas 2,3-dichloropyridine and 2,5-dichloro-4-(lithiooxy)pyridine undergo deprotonation exclusively at the 4- and 2-positions, resp., optional site selectivity can be implemented with 2,5- and 3,4-dichloropyridine (which are attacked, depending on the choice of the reagents, at either the 4- or 6- and either the 2- or 5-positions, resp.). Upon treatment with lithium diisopropylamide, 2,4-dichloro-3-iodopyridine, 3,5-dichloro-4-bromopyridine, and 2,6-dichloro-3-iodopyridine afford 5-, 2-, and 4-lithiated intermediates, but the latter isomerize instantaneously to species in which lithium and iodine have swapped places, the driving force being the low basicity of C-Li bonds when flanked by two neighboring halogens. [on SciFinder (R)]

Published in:
European Journal of Organic Chemistry, 7, 1371-1376
CAN 135:33422 27-16 Heterocyclic Compounds (One Hetero Atom) Section de Chimie (BCh), Universite,Lausanne,Switz. Journal 1434-193X written in English. 109-09-1 (2-Chloropyridine); 626-60-8 (3-Chloropyridine); 2402-77-9 (2,3-Dichloropyridine); 2402-78-0 (2,6-Dichloropyridine); 2457-47-8 (3,5-Dichloropyridine); 16110-09-1 (2,5-Dichloropyridine) Role: RCT (Reactant), RACT (Reactant or reagent) (regioselective functionalization of dichloropyridines); 14482-51-0P (2-Bromo-3,5-dichloropyridine); 26452-80-2P (2,4-Dichloropyridine); 55934-00-4P (3,4-Dichloropyridine); 78607-36-0P (2-Chloro-3-iodopyridine); 98027-84-0P; 148493-37-2P; 153034-86-7P (2-Chloro-4-iodopyridine); 343781-36-2P; 343781-45-3P; 343781-49-7P; 343781-57-7P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (regioselective functionalization of dichloropyridines); 1702-17-6P (3,6-Dichloro-2-pyridinecarboxylic acid); 5398-44-7P (2,6-Dichloro-4-pyridinecarboxylic acid); 55304-78-4P (2,6-Dibromo-3,5-dichloropyridine); 73027-79-9P; 81719-53-1P (3,5-Dichloro-2-pyridinecarboxylic acid); 88912-26-9P (2,5-Dichloro-4-pyridinecarboxylic acid); 184416-84-0P (2,3-Dichloro-4-pyridinecarboxylic acid); 262423-77-8P; 343781-41-9P; 343781-50-0P; 343781-51-1P; 343781-52-2P; 343781-53-3P; 343781-54-4P; 343781-55-5P; 343781-56-6P; 343781-58-8P Role: SPN (Synthetic preparation), PREP (Preparation) (regioselective functionalization of dichloropyridines)

 Record created 2006-03-03, last modified 2018-12-03

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