Coordination assembly enables highly selective catalytic hydroaminomethylation of olefins

Abstract

Hydroaminomethylation (HAM) of olefins constitutes one of the most promising and practical methods to produce amines, but control of the selectivity between linear and branched products is still challenging. Herein,...

Selective hydrogenation of phenols to cyclohexanols catalyzed by robust solid NHC–Rh coordination assemblies in water

“…Consequently, a hydrogenation curve of the model reaction of phenol was established, in which the key intermediate cyclohexanone accumulated in the first few hours and then was gradually hydrogenated. Based on these control experiments and previous reports, 52,62 a plausible mechanism is proposed in Fig. 3d.…”

“…To prevent the possible deactivation of NHC–Rh complexes via cluster formation during hydrogenation, 49 we employed the “self-supporting” strategy to fabricate NHC–Rh coordination assemblies. 52 Following our recent research interests in the development of novel NHC–metal catalysts, their immobilization strategy and further applications, 52–57 we demonstrated that NHC–Rh solid coordination assemblies were efficient catalysts for the selective hydrogenation of phenols (Fig. 1d).…”

“…58 Hence, a series of solid NHC–Rh coordination assemblies 5 and 6a–d were prepared according to our previous reports. 52 To our delight, solid 5 derived from the bis-benzoimidazolium salt resulted in a medium yield (65%). By increasing the aryl ring of the NHC ligand, a satisfactory conversion and high yield (94%) could be achieved using solid 6a in H 2 O under mild conditions (0.5 mol% catalyst loading at 30 °C and 5 bar H 2 ).…”

“…This might be due to the stronger σ-electron donor ability of the π-extended NHC ligands. 52 Inferior yields (45%-81%) were observed when using other solid assemblies 6b-d with different auxiliary ligands (CO) and counter-anions (I − or PF 6…”

“…Recently, we have demonstrated that “self-supporting” 52–57 is an effective strategy to improve the stabilities of NHC–M complexes due to the “isolation effect”. 58 Hence, a series of solid NHC–Rh coordination assemblies 5 and 6a–d were prepared according to our previous reports.…”