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Reduction of nitriles
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Diisopropylaminoborane [BH2N(iPr)2] in the
presence of a catalytic amount of lithium borohydride (LiBH4) reduces
a large variety of aliphatic and aromatic nitriles in excellent yields.BH2N(iPr)2
can also reduce nitriles in the presence of unconjugated alkenes and alkynes.
Unfortunately, selective reduction of a nitrile in the presence of an aldehyde
is not possible.
D. Haddenham, L. Pasumansky, J. DeSoto, S. Eagon, B. Singaram, J. Org. Chem., 2009,
74, 1964-1970.
A wide range of nitriles were reduced to primary amines by 1.2 equiv of
ammonia borane under thermal decomposition conditions without any catalyst to
primary amines in very good yields. The reactions are environmentally benign
with H2 and NH3 generated as byproducts. The reactions are
also tolerant of many functional groups.
M. Ding, J. Chang, J.-X. Mao, J. Zhang, X. Chen, J. Org. Chem., 2022, 87,
16230-16235.
The use of 9-BBN dimer as a catalyst and pinacolborane as a turnover reagent
enables an efficient hydroboration of nitriles to provide N,N-diborylamines,
which act as efficient synthons for the synthesis of primary amines and
secondary amides.
S. Pradhan, R. V. Sankar, C. Gunanathan, J. Org. Chem., 2022, 87,
12386-12396.
Solid amidophosphine boranes were synthesized to replace more commonly used
borane reagents. These compounds demonstrated excellent reactivity and
functional group tolerance toward a wide variety of nitriles, alkynes, and
carboxylic acids, affording the corresponding ammonium salts, alkenes, and
alcohols in good yield.
R. Kumar, R. K. Meher, J. Sharma, A. Sau, T. K. Panda, Org. Lett.,
2023, 25, 7923-7927.
A practical and cost-efficient reductive deuteration of nitriles under single-electron
transfer conditions enables the synthesis of α,α-dideuterio amines in
excellent yields using bench stable
and commercially available sodium dispersions and EtOD-d1.
Y. Ding, S. Luo, A. Adijiang, H. Zhao, J. An, J. Org. Chem., 2018, 83,
12269-12274.
Silylative reduction of nitriles under transition metal-free conditions converts
alkyl and (hetero)aryl nitriles efficiently to primary amines under mild
conditions. The use of sterically bulky silanes enabled a partial reduction
leading to N-silylimines.
N. Gandhamsetty, J. Jeong, Y. Park, S. Park, S. Chang, J. Org. Chem.,
2015,
80, 7281-7287.
The conversion of nitriles to silylated primary amines was achieved in the
presence of TMDS as the reducing agent, a catalytic
amount of Co(OPiv)2, and an isocyanide ligand. Acid hydrolysis or treatment with
acid chlorides provided the corresponding primary amines or imides in good yields.
A. Sanagawa, H. Nagashima, Org. Lett.,
2019, 21, 287-291.
Low loadings of AgSbF6 catalyze the hydroboration of nitriles,
alkens, and aldehydes under base- and solvent-free conditions. This
atom-economic chemoselective protocol shows excellent functional group tolerance
and compatibility with structurally and electronically diverse substrates.
V. K. Pandey, C. S. Tiwari, A. Rit, Org. Lett., 2021, 23,
1681-1686.
A conjugated bis-guanidinate (CBG)-supported aluminum dihydride complex
catalyzes a chemoselective hydroboration of various nitriles and alkynes. The
reaction leaves other reducible groups intact. Moreover, aluminum-catalyzed
hydroboration is expanded to more challenging substrates such as alkene,
pyridine, imine, carbodiimide, and isocyanides.
N. Sarkar, S. Bera, S. Nembenna, J. Org. Chem., 2020, 85,
4999-5009.
A simple [Ru(p-cymene)Cl2]2 complex is used as a
catalyst precursor in a catalyzed hydroboration of nitriles and imines using
pinacolborane with unprecedented catalytic efficiency.
A. Kaithal, B. Chatterjee, C. Gunanathan, J. Org. Chem.,
2016, 81, 11153-11161.
The ruthenium complex [(η6-p-cymene){(IMes)P}RuCl] was used
for efficient hydroborations of a wide range of nitriles, carboxylic
esters, and carboxamides in neat pinacolborane (HBpin) under comparatively mild
reaction conditions (60-80 �C, 3-5 mol % catalyst loading).
J. Bhattacharjee, D. Blockfeld, M. Tamm, J. Org. Chem., 2022, 87,
1098-1109.
A continuous flow method for the selective reduction of aromatic nitriles to the
corresponding primary amines is based on a ruthenium-catalysed
transfer-hydrogenation process with isopropanol as both solvent and reducing
agent.
R. Labes, D. Gonz�lez-Calder�n, C. Battilocchio, C. Mateos, G. R. Cumming, O.
de Frutos, J. A. Rinc�n, S. V. Ley,
Synlett, 2017, 28, 2855-2858.
Activation of SmI2 (Kagan’s reagent) with Lewis bases enables a mild
general reduction of nitriles to primary amines under single electron transfer
conditions. Activated samarium diiodide features excellent functional group
tolerance and is therefore an attractive alternative to pyrophoric alkali metal
hydrides. Notably, an electron transfer from Sm(II) to bench stable nitrile
precursors generates imidoyl-type radicals.
M. Szostak, B. Sautier, M. Spain, D. J. Procter, Org. Lett., 2014,
16, 1092-1095.
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.
The scope of nickel boride mediated reduction of nitriles has been extended
further to allow the preparation of Boc protected amines via a mild
catalytic process.
S. Caddick, D. B. Judd, A. K. de K. Lewis, M. T. Reich, M. R. V. Williams,
Tetrahedron, 2003, 59, 5417-5423.