Saturday, August 4, 2012

Iron-Catalyzed Formation of 2-Aminopyridines from Diynes and Cyanamides

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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