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(Dimethoxy‐ and Dihalopyridyl)boronic Acids and Highly Functionalized Heteroarylpyridines by Suzuki Cross‐Coupling Reactions
Author(s) -
Smith Amy E.,
Clapham Kate M.,
Batsanov Andrei S.,
Bryce Martin R.,
Tarbit Brian
Publication year - 2008
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/ejoc.200701156
Subject(s) - chemistry , boronic acid , suzuki reaction , pyridine , boron , metalation , coupling reaction , intramolecular force , ring (chemistry) , medicinal chemistry , organic chemistry , catalysis , palladium
We report the synthesis of (2,6‐dimethoxy‐3‐pyridyl)boronic acid ( 2 ), (2,3‐dimethoxy‐4‐pyridyl)boronic acid ( 4 ), (2,6‐difluoro‐3‐pyridyl)boronic acid ( 6 ), (2,6‐dichloro‐3‐pyridyl)boronic acid ( 8 ) and (2,3‐dichloro‐4‐pyridyl)boronic acid ( 10 ) by directed ortho ‐metalation reactions on the corresponding disubstituted pyridine precursor, followed by the reaction with triisopropyl borate (TPB) or trimethyl borate. Thereactivity of the pyridylboronic acids with heteroaryl halides in Suzuki–Miyaura cross‐coupling reactions has been evaluated. New highly functionalized heteroarylpyridine derivatives have thereby been obtained in moderate to high yields. The reaction of 8 and 3‐amino‐2‐chloropyridine yielded the rare 5 H ‐pyrrolo[2,3‐ b :4,5‐ b′ ]dipyridine (i.e. 1,5‐diazacarbazole) ring system by sequential cross‐coupling and intramolecular cyclisation reactions. The X‐ray crystal structures are reported for the pyridylboronic acids 2 , 4 , 8 and 10 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)