Structural and synthetic insights into pyridine homocouplings mediated by a β-diketiminato magnesium amide complex

Hevia, Eva and McLellan, Ross and Davin, Laia and Clegg, William and Kennedy, Alan and Probert, Michael R (2018) Structural and synthetic insights into pyridine homocouplings mediated by a β-diketiminato magnesium amide complex. Chemistry - A European Journal. ISSN 0947-6539

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    Abstract

    Reaction of [(DippNacnac)Mg(TMP)] (1) with 4‐subtituted pyridines proceeds via sequential regioselective metalation and 1,2‐addition to furnish a range of symmetric 4,4'R2‐2,2'‐bipyridines in good yield, representing a new entry into bipyridine synthesis. Interestingly, the reaction with 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 [DippNacnacMgOMe]2 (7). Synthesis combined with spectroscopic and structural analysis help rationalise the underlying processes resulting in the observed reactivity, and elucidates the key role of the sterically encumbered β‐diketiminate ligand plays in determining regioselectivity.