Selective Reduction of Nitroarenes with Silanes Catalyzed by Nickel N‐Heterocyclic Carbene Complexes

Abstract

An efficient catalytic system for the reduction of nitroarenes to amines was developed using a well‐defined nickel–NHC (N‐heterocyclic carbene) complex as catalyst and phenylsilane as reducing agent. The excellent activity of the catalyst provides access to anilines containing a wide array of reactive functionalities at 20 °C, and without using any base or additive. Notably, the catalytic system allows the reduction of 5,10,15,20‐tetra‐(nitrophenyl)porphyrin (TNPP) and CuII β‐nitroporphyrin to the corresponding aminoporphyrins.

Reduction of Nitro Compounds Using 3d-Non-Noble Metal Catalysts

“…429 A faster reduction of a number of nitroarenes was obtained using either an abnormal N-heterocyclic carbene based nickel complex, NiCl2(aNHC)2, (aNHC = 1,3-bis(2,6-diisopropylphenyl)-2,4-diphenyl-2,3-dihydro-1H-imidazole) 439 or a half-sandwich Ni-NHC complexes (Scheme 45). 440 Scheme 45 Half-sandwich Ni-NHC (left) 440 and abnormal NHC-Ni complex (right) 439 for the reduction of nitroarenes with silanes.…”

Highly Modular Piano-Stool N-Heterocyclic Carbene Iron Complexes: Impact of Ligand Variation on Hydrosilylation Activity

“…Despite these facts, iron was for a long time scarce in the catalytic literature compared to some of the more expensive, rare, and toxic metals in the periodic system. The application of iron as a molecular catalyst has been catching up with other metals over the last 20 years, however, and is now covering a plethora of organic reactions. − Hydrosilylation, one of the fields that has received much attention in iron catalysis during the past decades, − is a versatile methodology for the reduction of a variety of substrates under base-free conditions and without the need for highly reducing conditions as imparted by H 2 pressure. − In particular, hyydrosilylation of alkenes is industrially important due to the increasing demand for silanes and siloxanes …”

Microwave‐assisted reduction of aromatic nitro compounds with novel oxo‐rhenium complexes

“…[16,64,65] The organometallic catalysts containing a N-heterocyclic carbene that we considered perform as good as our systems, but they require milder condition than ours. [48,53,66] An interesting solution is the one offered by Sobhani et al, [66] which realized a catalyst (Pd-NHC-g-Fe 2 O 3 -nbutyl-SO 3 H) in which Pd is bound to an NHC anchored to a magnetic bead that is easy to recover thank to the use of an external magnetic field. This could be a useful system in cases like ours in which the amount of catalyst used is really tiny and the recovery of the catalyst for its reuse becomes challenging.…”

“…After that the S C H E M E 5 Proposed catalytic cycle for the reduction of nitro benzene performed by the catalytic system 5/PhSiH 3 . The reduction of nitrobenzene, took here as an example, takes place after an initial nitrosyl activation (step 2) and the loss of one of the pyridines as Py*HBr Sun et al [45] Ni-NHC 2.0 PhSiH 3 (5.0) 1.0 20 15 91 Lopes et al [48] PtIPr 0.05 H 2 (1 bar) 0.75 30 1.5 100 Lara et al [49] Pd (OAc) 2 0.05 PMHS(4.0) 1.0 RT 0.5 Solid mass…”

“…[ 16,64,65 ] The organometallic catalysts containing a N‐heterocyclic carbene that we considered perform as good as our systems, but they require milder condition than ours. [ 48,53,66 ]…”