ORGANIC
LETTERS
2008
Vol. 10, No. 2
221-223
Asymmetric Synthesis of C2-Symmetric
Vicinal Diamines via Reductive
Dimerization of N-Acylpyridinium and
Related Salts
Pandi Bharathi and Daniel L. Comins*
Department of Chemistry, North Carolina State UniVersity,
Raleigh, North Carolina 27695-8204
Received October 25, 2007
ABSTRACT
A new route to C2-symmetric diamines via an asymmetric reductive dimerization of 1-acylpyridinium salts and their benzo derivatives is
described. This method is practical as the starting heterocycles and chiral auxiliaries are readily available. The titanium reducing agent is
inexpensive and easy to prepare. Several novel enantiopure C2-symmetric diamine derivatives were synthesized using this method.
C2-Symmetric 1,2-diamines and their derivatives are impor-
tant in medicinal chemistry, natural products, coordination
chemistry, and asymmetric catalysis.1 They have been
extensively used as ligands and catalysts in asymmetric
synthesis with impressive results.2 Because they are so
effective as chiral ligands, much work has been reported on
the development of methods for their preparation.3 An
attractive approach to vicinal diamines is the reductive
coupling of imine species promoted by a metal reducing
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10.1021/ol702595d CCC: $40.75
© 2008 American Chemical Society
Published on Web 12/20/2007