Iron-Catalyzed Formation of 2-Aminopyridines from Diynes and Cyanamides
Timothy K. Lane, Brendan R D'Souza, and Janis Louie
http://pubs.acs.org.libproxy.mit.edu/doi/abs/10.1021/jo3012418
In this work, Fe(0) catalyzed 2+2+2 cycloaddition reactions of diynes or
terminal alkynes (2 equivalents) and cyanamides are reported. Fe(0) is
generated from the combination of Fe(II) complexes and Zn. This is an
exciting development b/c it allows relatively rapid and high yield
construction of highly (and even asymmetrically) substituted pyridines;
moreover, as mentioned above, one can use 2 equivalents of a terminal
alkyne instead of a diyne and get desired pyridine in high yield. In
addition, this reaction doesn't require large excess of nitrile
component, uses a simple ligand for Fe, and works well with a low
catalyst loading (5%). No other reagent system for similar
transformation can boast having these qualities.
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