Categories: N-H Bond Formation >
Deoxygenation of aza-aromatics
Recent Literature
A convenient and chemoselective method for deoxygenation of pyridine N-oxide
derivatives by transfer oxidation of triethylamine under microwave irradiation
is catalysed by [Pd(OAc)2]/dppf.
J. A. Fuentes, M. L. Clarke, Synlett, 2008,
2579-2582.
An electrochemical deoxygenation of N-heteroaromatic N-oxide provides the
corresponding N-heteroaromatics such as pyridines, quinolines, isoquinolines,
and phenanthridines efficiently in aqueous solution without the need for
transition-metal catalysts and waste-generating reducing reagents.
P. Xu, H.-C. Xu, Synlett, 2019,
30,
1219-1221.
Sulfoxides and aza-aromatic N-oxides were deoxygenated using a system
of indium and pivaloyl chloride at room temperature to give the
corresponding sulfides and aza-aromatics in high yields.
E. S. Park, S. Hwan, Lee, J. H. Lee, H. J. Rhee, C. M. Yoon, Synthesis, 2005, 3499-3501.
A mild and efficient general method for the deoxygenation of organic N-oxides
such as azoxybenzenes, N-arylnitrones, and N-heteroarene N-oxides
uses the environmentally friendly Lewis acids Zn(OTf)2 and
Cu(OTf)2.
A. Saini, S. Kumar, J. S. Sandhu, Synlett,
2006, 395-398.
Visible light-mediated metallaphotoredox catalysis enables a highly
chemoselective deoxygenation of N-heterocyclic N-oxides using
Hantzsch esters as the stoichiometric reductants and only a tiny amount of the
catalyst within a few minutes at room temperature. The reaction tolerates a wide
range of functional groups, such as carbamates, esters, ketones, nitrile groups,
nitro groups, and halogens.
J. H. An, K. D. Kim, J. H. Lee, J. Org. Chem., 2021, 86,
2876-2894.
Visible-light mediates a scalable and operationally simple method for the
chemoselective deoxygenation of a wide range of N-heterocyclic N-oxides
at room temperature using only commercially available reagents. This protocol
offers an unprecedented chemoselective removal of the oxygen atom in a quinoline
N-oxide in the presence of a pyridine N-oxide through the
judicious selection of the photocatalyst.
K. D. Kim, J. H. Lee, Org. Lett.,
2018, 20, 7712-7716.