Mild and selective hydrogenation of aromatic and aliphatic (di)nitriles with a well-defined iron pincer complex

Abstract

The catalytic hydrogenation of carboxylic acid derivatives represents an atom-efficient and clean reduction methodology in organic chemistry. More specifically, the selective hydrogenation of nitriles offers the possibility for a green synthesis of valuable primary amines. So far, this transformation lacks of useful, broadly applicable non-noble metal-based catalyst systems. In the present study, we describe a molecular-defined iron complex, which allows for the hydrogenation of aryl, alkyl, heterocyclic nitriles and dinitriles. By using an iron PNP pincer complex, we achieve very good functional group tolerance. Ester, ether, acetamido as well as amino substituents are not reduced in the presence of nitriles. Moreover, nitriles including an α,β-unsaturated double bond and halogenated derivatives are well tolerated in this reaction. Notably, our complex constitutes the first example of an homogeneous catalyst, which permits the selective hydrogenation of industrially important adipodinitrile to 1,6-hexamethylenediamine.

Isomerization of Allylic Alcohols to Ketones Catalyzed by Well‐Defined Iron PNP Pincer Catalysts

“…[11] The groups of Schneider, [11g] Guan, [12] and Beller [13] independently reportedt he synthesis of iron compound A (Scheme 2), which is an effective catalyst for the hydrogenation of esters, [12][13][14] nitriles, [15] and heterocycles. [11] The groups of Schneider, [11g] Guan, [12] and Beller [13] independently reportedt he synthesis of iron compound A (Scheme 2), which is an effective catalyst for the hydrogenation of esters, [12][13][14] nitriles, [15] and heterocycles.…”

Iron-catalyzed reduction of carboxylic and carbonic acid derivatives

“…investigated their use in hydrogenation of nitrile derivatives[50]. After screening all the reaction parameters (solvent, temperature, hydrogen pressure, catalyst loading) in the reduction of 4-phenylbenzonitrile, the optimized conditions were the following: 30 bar of hydrogen at 70°C in iso-propanol in the presence of 1 mol% of [(PNP)Fe(H)(HBH 3 )(CO)] complex Fe11.…”

Amido PNP complexes of iridium: Synthesis and catalytic olefin and alkyne hydrogenation

“…Interestingly, stilbene, though an internal olefin that is produced from hydrogenation of diphenylacetylene (entries 17–18), is more reactive than styrene (entries 15–16). Attempts to hydrogenate nitriles, however, were not successful (entries 19–22). Collectively, the catalytic activity of 2a is comparable to that of 4b .…”