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Comparative Study on the Reactivity of 6‐Haloimidazo[1,2‐ a ]pyridine Derivatives towards Negishi‐ and Stille ‐Coupling Reactions
Author(s) -
Hervet Maud,
Théry Isabelle,
Gueiffier Alain,
EnguehardGueiffier Cécile
Publication year - 2003
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200390290
Subject(s) - negishi coupling , stille reaction , chemistry , pyridine , yield (engineering) , coupling reaction , combinatorial chemistry , medicinal chemistry , organic chemistry , reagent , catalysis , materials science , metallurgy
The scope of the Suzuki ‐cross‐coupling reaction of 6‐haloimidazo[1,2‐ a ]pyridines is dependent on the availability of the (hetero)arylboronic acids. Thus, with the aim to develop expanded applications of (hetero)arylations of imidazo[1,2‐ a ]pyridines, we investigated the Negishi ‐ and Stille ‐cross‐coupling reactions at the 6‐position. Remarkably, attempts to apply the Negishi ‐cross‐coupling conditions to the organozinc derivative prepared from 6‐haloimidazo[1,2‐ a ]pyridine via a lithiumzinc exchange led to the 5‐phenyl compound 3 in 54% yield instead of the desired 6‐phenyl isomer ( Scheme 1 ). In contrast, various commercially available halogenated five‐ or six‐membered‐ring heterocycles were efficiently coupled to the 6‐(trialkylstannyl)imidazo[1,2‐ a ]pyridine under Stille conditions ( Table 2 ).