Catalytic hydrogenation of α,β-unsaturated carboxylic acid derivatives using copper(i)/N-heterocyclic carbene complexes

Abstract

A simple and air-stable copper(i)/N-heterocyclic carbene complex enables the catalytic hydrogenation of enoates and enamides, hitherto unreactive substrates employing homogeneous copper catalysis and H2 as a terminal reducing agent.

A Bifunctional Copper Catalyst Enables Ester Reduction with H2: Expanding the Reactivity Space of Nucleophilic Copper Hydrides

“…When ester 13b was subjected to identical conditions, a similarly high isotope labeling was found in the α-position of the alcohol 14b- d 4 , in addition to significant deuteration (92% D) in the β-position. The latter can be explained by a prior formation of an ester enolate of 13b under the basic reaction conditions followed by quenching with DO t Bu, stemming from the heterolytic activation of D 2 . − …”

“…In earlier studies from our laboratories we have studied the generation of nucleophilic copper­(I) hydrides from dihydrogen (H 2 ) . In this vein, we have established that copper­(I)/ N -heterocyclic carbene (NHC) complexes bearing a Cu–O bond are preactivated for the heterolytic cleavage of H 2 into a formal proton and hydride equivalent. , The thus-generated copper­(I) hydrides can be employed in a catalytic setting for hydrogenations or hydride transfer reactions …”

Mild and Efficient Heterogeneous Hydrogenation of Nitroarenes Facilitated by a Pyrolytically Activated Dinuclear Ni(II)-Ce(III) Diimine Complex

“…Additionally, the described heterogeneous hydrogenation also worked out well with isophorone d7 whereas the attachment of an amino group directly to the C-C double bond proved to be deleterious for the conjugate hydrogenation since we did not detect any tagged cyclohexanone e8 . Of note, the chemoselective reduction of α,β -unsaturated carbonyl compounds using gaseous H 2 is usually the realm of copper catalysis [ 124 , 125 ], whereas only recently a manganese-based system was described [ 126 ].…”

Catalytic Performances of Platinum Containing PLLA Macrocomplex in the Hydrogenation of α,β-Unsaturated Carbonyl Compounds

“…This normally induces a severe decrement of the hydrogenation selectivity and an interesting case study is represented by the α,β-unsaturated carbonyl compounds [9]. Over the years, several systems have been developed for the selective hydrogenation of these substrates based on a plethora of metal frameworks (i.e., Cu [10], Au [11], Ni [12], Rh [13], Ru [14], Pd [15], and Pt [16,17]) with the aim to obtain a selective reduction of carbon-carbon or carbon-oxygen double bond or both. Among all available catalysts, noble metal based nanoparticles have astonishing properties of selectivity but still require a complex multi-step synthesis [18][19][20][21].…”