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Structural and Synthetic Insights into Pyridine Homocouplings Mediated by a β‐Diketiminato Magnesium Amide Complex
Author(s) -
Davin Laia,
Clegg William,
Kennedy Alan R.,
Probert Michael R.,
McLellan Ross,
Hevia Eva
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201803297
Subject(s) - regioselectivity , chemistry , steric effects , pyridine , amide , reactivity (psychology) , yield (engineering) , stereochemistry , bipyridine , ligand (biochemistry) , medicinal chemistry , magnesium , combinatorial chemistry , organic chemistry , catalysis , crystal structure , receptor , medicine , biochemistry , materials science , alternative medicine , pathology , metallurgy
The reaction of [( Dipp Nacnac)Mg(TMP)] ( 1 ) with 4‐subtituted pyridines proceeds via sequential regioselective metallation and 1,2‐addition to furnish a range of symmetric 4,4′‐R 2 ‐2,2′‐bipyridines in good yield, representing a new entry into bipyridine synthesis. Interestingly, the reaction of 1 with 2‐OMe‐pyridine led to formation of asymmetric bipyridine 6 , resulting from the C6‐magnesiation of the heterocycle followed by a C−C coupling step by addition to the C2 position of a second, non‐metallated molecule, and subsequent elimination of [ Dipp NacnacMgOMe] 2 ( 7 ). Synthesis combined with spectroscopic and structural analysis help rationalise the underlying processes resulting in the observed reactivity, and elucidate the key role that the sterically encumbered β‐diketiminate ligand plays in determining regioselectivity.