Iridium-Catalyzed Transfer Hydrogenation of 1,10-Phenanthrolines using Formic Acid as the Hydrogen Source

Co(II)-Catalyzed Additive-Free Transfer Hydrogenation of N-Heteroarenes at Room Temperature

Traditional catalyst development relies on multistep synthesis and isolation of ligand and precatalyst. Designing a catalytic system that can be assembled in situ from easily accessible starting materials can decrease the reaction complexity and enhance the synthetic utility. Herein, we report an inexpensive and commercially available CoBr2·H2O/terpyridine-catalyzed effective and straightforward transfer hydrogenation (TH) protocol for N-heteroarenes, utilizing NH3·BH3 (AB) under ambient conditions. Synthesis of diverse substrates and bioactive molecules demonstrated a practical applicability. Control experiments and DFT studies elucidate the mechanism.

Methyl Formate, an Alternative Transfer Hydrogenating Agent for Chemoselective Reduction of N-Heteroarenes and Azoarenes

The search for efficient molecular hydrogen precursors and their catalytic exploration is necessary for the evolution of catalytic transfer hydrogenation. Methyl formate (MF) having high hydrogen content still remains unexplored for such transformations. Herein, we disclosed a bifunctional Ir(III)-complex catalyzed chemoselective TH protocol for N-heteroarenes and azoarenes using MF. A variety of substrates including ten bioactive molecules have been synthesized under mild reaction conditions. A probable mechanistic pathway was proposed based on control experiments and mechanistic studies.

Fluorine in metal-catalyzed asymmetric transformations: the lightest halogen causing a massive effect

This review aims at providing an overview of the most significant applications of fluorine-containing ligands reported in the literature starting from 2001 until mid-2021. The ligands are classified according to the nature of the donor atoms involved. This review highlights both metal-ligand interactions and the structure-reactivity relationships resulting from the presence of the fluorine atom or fluorine-containing substituents on chiral catalysts.

The mechanism of direct reductive amination of aldehyde and amine with formic acid catalyzed by boron trifluoride complexes: insights from a DFT study

A volcano diagram of BF3 catalytic species and their activities was proposed for the DRA of aldehyde and amine with formic acid.

Enhanced Catalytic Activity of Iridium(III) Complexes by Facile Modification of C,N-Bidentate Chelating Pyridylideneamide Ligands

A set of aryl-substituted pyridylideneamide (PYA) ligands with variable donor properties owing to a pronounced zwitterionic and a neutral diene-type resonance structure were used as electronically flexible ligands at a pentamethylcyclopentadienyl (Cp*) iridium center. The straightforward synthesis of this type of ligand allows for an easy incorporation of donor substituents such as methoxy groups in different positions of the phenyl ring of the C,N-bidentate chelating PYA. These modifications considerably enhance the catalytic activity of the coordinated iridium center toward the catalytic aerobic transfer hydrogenation of carbonyls and imines as well as the hydrosilylation of phenylacetylene. Moreover, these PYA iridium complexes catalyze the base-free transfer hydrogenation of aldehydes, and to a lesser extent also of ketones. Under standard transfer hydrogenation conditions including base, aldehydes are rapidly oxidized to carboxylic acids rather than reduced to the corresponding alcohol, as is observed under base-free conditions.