Categories: C-H Bond Formation >
Reduction of amides to amines
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Recent Literature
Y[N(TMS)2]3 is an efficient homogeneous
catalyst for the hydroboration of secondary amides and tertiary amides
to provide the corresponding amines. The reaction tolerates various functional
groups such as cyano, nitro, and vinyl groups.
P. Ye, Y. Shao, X. Ye, F. Zhang, R. Li, J. Sun, B. Xu, J. Chen,
Org. Lett., 2020, 22, 1265-1269.
The combination of triethylborane
with an alkali metal base catalyzes the reduction of amides with silanes
to form amines under mild conditions. In addition, a selective transformation
of secondary amides to aldimines and primary amides to nitriles can also be
achieved.
W. Yao, H. Fang, Q. He, D. Peng, G. Liu, Z. Huang, J. Org. Chem., 2019, 84,
6084-6093.
Transition-metal-free catalytic protocols for controlled reduction of amide
functions using cheap and bench-stable hydrosilanes as reducing agents enable
the selective reduction of unactivated C-O bonds in amides. By altering the
hydrosilane and solvent, the C-N bonds selectively breaks via a
deacylative cleavage.
W. Yao, L. He, D. Han, A. Zhong, J. Org. Chem., 2019, 84,
14627-14635.
A nickel-catalyzed reduction of secondary and tertiary amides provides amines.
The reaction transforms various amide substrates, proceeds in the presence of
esters and epimerizable stereocenters, and can be used to achieve the reduction
of lactams. Moreover, this methodology provides a simple tactic for accessing
medicinally relevant α-deuterated amines.
B. J. Simmons, M. Hoffmann, J. Hwang, M. K. Jackl, N. K. Garg, Org. Lett.,
2017, 19, 1910-1913.
1,1,3,3-tetramethyldisiloxane and 1,2-bis(dimethylsilyl)benzene are found to be
effective reducing agents for a platinum-catalyzed reduction of carboxamides to
amines. The reaction tolerates other reducible functional groups such as NO2,
CO2R, CN, C═C, Cl, and Br. The product is obtained by simple
extraction.
S. Hanada, E. Tsutsumi, Y. Motoyama, H. Nagashima, J. Am. Chem. Soc., 2009,
131, 15032-15040.
A zinc-catalyzed reduction of tertiary amides shows remarkable chemoselectivity
and substrate scope tolerating ester, ether, nitro, cyano, azo, and keto
substituents.
S. Das, D. Addis, S. Zhou, K. Junge, M. Beller, J. Am. Chem. Soc., 2010,
132, 1770-1771.
The combination of amide activation by Tf2O with B(C6F5)3-catalyzed
hydrosilylation with TMDS enables a one-pot reduction of secondary amides to
amines under mild conditions with broad applicability and excellent
chemoselectivity for many sensitive functional groups.
P.-Q. Huang, Q.-W. Lang, Y.-R. Wang, J. Org. Chem.,
2016,
81, 4235-4243.
Diethylzinc (Et2Zn) is an efficient and chemoselective catalyst for
the reduction of tertiary amides under mild reaction conditions employing
polymeric silane (PMHS) as a cost-effective hydride source. Crucial for the
catalytic activity was the addition of a substoichiometric amount of lithium
chloride. A series of amides containing different additional functional groups
were reduced to their corresponding amines in very good yields.
O. O. Kovalenko, A. Volkov, H. Adolfsson, Org. Lett.,
2015,
17, 446-449.
Tris(pentafluorophenyl)boron B(C6F5)3 is an
effective catalyst for the reduction of tertiary and N-phenyl secondary
amides in the presence of a silane. Various amides can be reduced in near
quantitative yield, with minimal purification, at low temperatures, and with
short reaction times. This reduction tolerates alkenes, nitro groups, and aryl
halides, including aryl iodides.
R. C. Chadwick, V. Kardelis, P. Lim, A. Adronov, J. Org. Chem., 2014,
79, 7728-7733.
Reduction of secondary amides to imines and secondary amines has been achieved
using low catalyst loadings of readily available iridium catalysts such as
[Ir(COE)2Cl]2 with diethylsilane as reductant. The
stepwise reduction to secondary amine proceeds through an imine intermediate
that can be isolated when only 2 equiv of silane is used. This system shows high
efficiency and an appreciable level of functional group tolerance.
C. Cheng, M. Brookhart, J. Am. Chem. Soc., 2012,
134, 11304-11307.
An expeditious and practical method for the reduction of various amides and
lactams to amines in good to excellent yields is consisted of activation with Tf2O
followed by reduction with sodium borohydride in THF at room temperature. This
method offers TBDPS-group tolerance, short reaction time, and a simple workup.
S.-H. Xiang, J. Xu, H.-Q. Yuan, P.-Q. Huang, Synlett, 2010,
1829-1832.
A chemoselective activation of a secondary amide with triflic anhydride in the
presence of 2-fluoropyridine enables a mild reduction using triethylsilane, a
cheap and rather inert reagent. Imines can be isolated after a basic workup or
readily transformed to the aldehydes following an acidic workup. The amine
moiety can be accessed by addition of Hantzsch ester to the reaction mixture.
G. Pelletier, W. S. Bechara, A. B. Charette, J. Am. Chem. Soc., 2010,
132, 12817-12819.
A triruthenium cluster catalyzes the reaction of secondary amides with
hydrosilanes, yielding a mixture of secondary amines, tertiary amines, and silyl
enamines. Production of secondary amines with complete selectivity is achieved
by the use of higher concentration of the catalyst and bifunctional hydrosilanes
such as 1,1,3,3-tetramethyldisiloxane followed by acidic workup.
S. Hanada, T. Ishida, Y. Motoyama, H. Nagashima, J. Org. Chem.,
2007,
72, 7551-7559.
The combination of B2pin2 and KOtBu enables a
chemoselective, metal-free reduction of aromatic nitro compounds to the
corresponding amines in very good yields in isopropanol. The reaction tolerates
various reducible functional groups.
H. Lu, Z. Geng, J. Li, D. Zou, Y. Wu, Y. Wu, Org. Lett.,
2016, 18, 2774-2776.
Phenol carbamates undergo an anionic ortho-Fries rearrangement to
their corresponding amides in the presence of LDA. Sterically hindered
substrates can be converted with s-BuLi/TMEDA at -90°C. The amides can be efficiently reduced with lithium aluminum hydride
to the corresponding Mannich bases.
N. Assimomytis, Y. Sariyannis, G. Stavropoulos, P. G. Tsoungas, G. Varvounis, P.
Cordopatis, Synlett, 2009,
2777-2782.
Odorless Dod-S-Me and MMS are developed as efficient borane carriers. The
yields of hydroborations and reductions with the borane complex of Dod-S-Me
are very high. The recovery of Dod-S-Me after the reaction is quantitative.
P. K. Patra, K. Nishide, K. Fuji, M. Node, Synthesis, 2004,
1003-1006.