Sodium cyanoborohydride, Sodium cyanotrihydroborate
Sodium cyanoborohydride is especially suitable for reductive aminations. Since the reaction rate for the reduction of iminium ions is much faster than for ketones or even aldehydes, the reductive amination can be carried out as a one-pot procedure by introducing the reducing agent into a mixture of the amine and carbonyl compound.
Contact with strong acids liberates the highly toxic gas HCN. A safer reducing agent with comparable reactivity is sodium triacetoxyborohydride.
Recent Literature
Branched imines were obtained in good to excellent yield (up to 99%) in a
highly regioselective intermolecular hydroamination of terminal alkynes with
various primary aromatic and aliphatic amines using an aryloxotitanium
complex. Subsequent reduction gave secondary amines in good yields.
V. Khedkar, A. Tillak, M. Beller, Org. Lett., 2003, 5, 4767-4770.
Manganese dioxide is employed as an in situ oxidant for the one-pot conversion
of alcohols into imines. In combination with polymer-supported cyanoborohydride
(PSCBH), a one-pot oxidation-imine formation-reduction sequence enables alcohols
to be converted directly into both secondary and tertiary amines.
L. Blackburn, R. J. K. Taylor, Org. Lett., 2001, 3, 1637-1639.
The selective aldimine cross-coupling represents a simple and flexible
method for the synthesis of highly substituted unsymmetrical
1,2-diamines. In addition, either the syn- or anti-configurated
vicinal diamine can be obtained, depending on the choice of the workup
and reduction conditions.
C. Kison, N. Meyer, T. Opatz, Angew. Chem., 2005, 117, 5807-5809.
A Lewis acid-catalyzed three-component, mild, highly atom econocial, direct-type
Mannich reaction of simple aromatic and enolizable aliphatic aldehydes,
secondary amines, and glycine derivatives affords various synthetically important
anti-α,β-diamino
ester derivatives in high yields with high diastereoselectivities.
M. M. Salter, J. Kobayashi, Y. Shimizu, S. Kobayashi, Org. Lett.,
2006, 8, 3533-3536.
