Reductive functionalization of the C=O unit in carboxylic acids, carbonic acid derivatives, and ultimately in carbon dioxide itself is a challenging task of key importance for the synthesis of value-added chemicals. In particular, it can open novel pathways for the valorization of non-fossil feedstocks. Catalysts based on earth-abundant, cheap, and benign metals would greatly contribute to the development of sustainable synthetic processes derived from this concept. Herein, a manganese pincer complex [Mn(Ph2PCH2SiMe2)2NH(CO)2Br] (1) is reported to enable the reduction of a broad range of carboxylic acids, carbonates, and even CO2 using pinacolborane as reducing agent. The complex is shown to operate under mild reaction conditions (80–120 °C), low catalyst loadings (0.1–0.2 mol%) and runs under solvent-less conditions. Mechanistic studies including crystallographic characterisation of a borane adduct of the pincer complex (1) imply that metal-ligand cooperation facilitates substrate activation.

A detailed overview for homogeneously catalyzed strategies and synthesis pathways using a combination of CO2, CO, and H2 as active building blocks to selectively obtain C1–C4 alcohols is presented. Conceptual strategies applying homologation, carbonylation, hydrocarboxylation, and hydrogenation reactions will be discussed, finally combining the individual reaction approaches towards potential new pathways to the envisaged alcohol products. Also, tailored reactor concepts with adapted recycling/separation methods for the molecular catalyst systems will be shown and discussed.

Herein, we report the synthesis, characterization, and catalytic performance of cationic Pd(II)−Anthraphos complexes in the intermolecular hydroamination of aromatic alkynes with aromatic amines. The reaction proceeds with 0.18 mol % of catalyst loading, at 90 °C for 4 h under neat conditions. Good to excellent yields could be obtained for a broad range of amines and alkynes.

Abstract:The catalytic reduction of esters using H2 offers a more sustainable alternative compared to classic stoichiometric reagents. Nowadays a wide range of highly efficient homogeneous catalysts are known, but these suffer from poor catalyst recoverability. Therefore, most industrial applications are based on heterogeneous catalysts but these processes are generally operated under harsh conditions (>200 °C, >100 bar). Here we describe the first catalytic system which combines the activity of homogeneous catalysts with the recoverability of a heterogeneous catalyst. The presented system is capable of hydrogenating esters under very mild conditions (25 °C, 50 bar) and could easily be recovered. The catalyst is based on phosphorus ligands covalently attached to a polymeric support and could be readily obtained via a facile solidphase synthetic protocol in high yields with minimal work-up.