Categories: N-H Bond Formation >
Reduction of imines
| Related |  Reductive Amination |
Recent Literature
Asymmetric reduction of ketimines with trichlorosilane can be catalyzed by
N-methylvaline-derived Lewis-basic formamides with high enantioselectivity
and low catalyst loading at room temperature in toluene. Appending a fluorous
tag to the catalyst simplifies the isolation procedure and allows the catalyst
to be recycled.
A. V. Malkov, M. Figlus, S. Stončius, P. Kočovský, J. Org. Chem., 2007,
72, 1315-1325.
L-Piperazine-2-carboxylic acid derived N-formamides are highly
enantioselective Lewis basic catalysts for the hydrosilylation of imines
with trichlorosilane. High isolated yields and enantioselectivities were
obtained for a broad range of substrates, including aromatic and aliphatic
ketimines.
Z. Wang, M. Cheng, P. Wu, S. Wei, J. Sun, Org. Lett.,
2006, 8, 3045-3048.
L-Pipecolinic acid derived formamides are highly efficient and
enantioselective Lewis basic organocatalysts for the mild reduction of
various N-aryl imines with trichlorosilane.
Z. Wang, X. Ye, S. Wei, P. Wu, A. Zhang, J. Sun, Org. Lett.,
2006, 8, 999-1001.
α-Imino esters derived from aryl and alkyl keto esters could be reduced
to the corresponding α-amino esters in excellent yields and in high enantiomeric
excesses using 5 mol-% of a chiral phosphoric acid as catalyst, Hantzsch ester
as hydride donor, and toluene as solvent.
G. Li, Y. Liang, J. C. Antilla, J. Am. Chem. Soc., 2007,
129, 5830-5831.
A simple and convenient procedure allows the reductive amination of aldehydes
and ketones using sodium borohydride as reducing agent and boric acid, p-toluenesulfonic
acid monohydrate or benzoic acid as activator under solvent-free conditions.
B. T. Cho, S. K. Kang, Tetrahedron, 2005,
61, 5725-5734.
The combination of HMPA and SmBr2 in THF is a powerful reductant
that is capable of reducing ketimines and alkyl chlorides at room
temperature.
B. W. Knettle, R. A. Flowers, II, Org. Lett., 2001, 3,
2321-2324.
The organic reductant 1-acetyl-2,3-dimethylimidazolidine is able to directly
reduce a series of aromatic, aliphatic and α,β-unsaturated aldehydes as well as
imines in high yields.
D. Li, Y. Zhang, G. Zhou, W. Guo, Synlett, 2008,
225-228.
Various benzaldimines and ketimines can be hydrosilated efficiently with PhMe2SiH
employing B(C6F5)3 as a catalyst. Spectral
evidence supports the intermediacy of a silyliminium cation with a hydridoborate
counterion formed via abstraction of a hydride from PhMe2SiH by B(C6F5)3
in the presence of imines.
J. M. Blackwell, E. R. Sonmor, T. Scoccitti, W. E.
Piers, Org. Lett., 2000, 2, 3921-3923.
A novel process for the efficient, enantioselective hydrosilylation of
ketimines based on catalytic amounts of copper hydride, (R)-DTBM-SEGPHOS,
and an inexpensive silane (tetramethyldisiloxane, TMDS) has been developed.
The resulting products are converted to their free-base form upon mild
hydrolysis.
B. H. Lipshutz, H. Shimizu, Angew. Chem. Int. Ed., 2004,
43, 2228-2230.
An aryloxotitanium complex is a highly chemo- and regioselective catalyst for
intermolecular hydroamination of terminal alkynes. Branched imines are obtained
in good yield with various primary aromatic and aliphatic amines.
V. Khedkar, A. Tillak, M. Beller, Org. Lett., 2003, 5,
4767-4770.
