Silyl-mediated halogen/halogen displacement in pyridines and other heterocycles

Heating with bromotrimethylsilane converts 2-chloropyridine into 2-bromopyridine and 2-chloro-6-methylpyridine into 2-bromo-6-methylpyridine. Both 2-chloropyridines and 2-bromopyridines give the corresponding iodo compd. when treated with in situ generated iodotrimethylsilane. Although 3- and 4-chloropyridine are completely inert, 2,4-dichloropyridine undergoes the halogen/halogen exchange simultaneously at the 2- and 4-position. Halogen displacement takes place exclusively at the 2-position with 2,3-dichloropyridine and 2,5-dichloropyridine. In agreement with the intermediacy of N-trimethylsilylpyridinium salts as a prerequisite for the occurrence of halogen exchange, neither 2-fluoropyridine and 2-fluoro-6-methylpyridine nor any 2,6-dihalopyridine reacts. Finally, bromine/chlorine and iodine/chlorine substitution can also be accomplished with 2- or 4-chloroquinoline, 1-chloroisoquinoline, 2-chloropyrimidine, chloropyrazine, and 2,3-dichloroquinoxaline as substrates. [on SciFinder (R)]

Published in:
European Journal of Organic Chemistry, 24, 4181-4184
CAN 138:321108 27-16 Heterocyclic Compounds (One Hetero Atom) Institut de Chimie moleculaire et biologique,Ecole Polytechnique Federale,Lausanne,Switz. Journal 1434-193X written in English. 86-98-6 (4,7-Dichloroquinoline); 109-09-1 (2-Chloropyridine); 612-62-4 (2-Chloroquinoline); 1722-12-9 (2-Chloropyrimidine); 2213-63-0; 2402-77-9 (2,3-Dichloropyridine); 2857-97-8 (Bromotrimethylsilane); 14508-49-7 (Chloropyrazine); 16029-98-4 (Iodotrimethylsilane); 16110-09-1 (2,5-Dichloropyridine); 18368-63-3 (2-Chloro-6-methylpyridine); 19493-44-8 (1-Chloroisoquinoline); 26452-80-2 (2,4-Dichloropyridine) Role: RCT (Reactant), RACT (Reactant or reagent) (silyl-mediated halogen/halogen exchange reactions of pyridines and other heterocycles); 109-04-6P (2-Bromopyridine); 5315-25-3P (2-Bromo-6-methylpyridine) Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (silyl-mediated halogen/halogen exchange reactions of pyridines and other heterocycles); 624-28-2P (2,5-Dibromopyridine); 1532-71-4P (1-Bromoisoquinoline); 2005-43-8P (2-Bromoquinoline); 4595-60-2P (2-Bromopyrimidine); 5029-67-4P (2-Iodopyridine); 6560-83-4P (2-Iodoquinoline); 19658-77-6P (1-Iodoisoquinoline); 23719-78-0P (2,3-Dibromoquinoxaline); 56423-63-3P (Bromopyrazine); 58530-53-3P (2,4-Dibromopyridine); 62674-71-9P (2-Iodo-6-methylpyridine); 77332-89-9P (2-Iodo-3-chloropyridine); 96424-68-9P (2-Bromo-3-chloropyridine); 98519-65-4P; 244221-57-6P Role: SPN (Synthetic preparation), PREP (Preparation) (silyl-mediated halogen/halogen exchange reactions of pyridines and other heterocycles)
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 Record created 2006-03-03, last modified 2018-01-27

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