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Silyl‐Mediated Halogen/Halogen Displacement in Pyridines and Other Heterocycles
Author(s) -
Schlosser Manfred,
Cottet Fabrice
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200212)2002:24<4181::aid-ejoc4181>3.0.co;2-m
Subject(s) - halogen , chemistry , chlorine , bromine , silylation , inert , halogenation , iodine , medicinal chemistry , halogen bond , organic chemistry , catalysis , alkyl
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 compound 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002)