Azole-Directed Cobalt-Catalyzed Asymmetric Hydrogenation of Alkenes

Cobalt-Catalyzed Asymmetric Hydrogenation of α-Hydroxy Ketones Enabled by a Carboxylic Acid Additive Promotion Strategy

Highly enantioselective hydrogenation of α-hydroxy ketones was achieved by applying the catalytic combination of cobalt acetate and chiral Ph-BPE ligand, supplemented by a carboxylic acid additive promotion strategy. The carboxylic acid additive significantly increases both reactivity and enantioselectivity, allowing for the highly efficient generation of chiral 1,2-diols with up to 99% ee. The application utility is proved through derivations and a total synthesis of (R)-(-)-eliprodil. Mechanistic studies, including control experiments and DFT calculations, support the proposed catalytic mechanism and explain the origin of enantioselectivity.

Chiral bisphosphine Ph-BPE ligand: a rising star in asymmetric synthesis

Chiral 1,2-bis(2,5-diphenylphospholano)ethane (Ph-BPE) is a class of optimal organic bisphosphine ligands with C2-symmetry. Ph-BPE with its excellent catalytic performance in asymmetric synthesis has attracted much attention of chemists with increasing popularity and is growing into one of the most commonly used organophosphorus ligands, especially in asymmetric catalysis. Over two hundred examples have been reported since 2012. This review presents how Ph-BPE is utilized in asymmetric synthesis and how powerful it is as a chiral ligand or even a catalyst in a wide range of reactions including applications in the total synthesis of bioactive molecules.

Asymmetric Hydrogenation of Indazole-Containing Enamides Relevant to the Synthesis of Zavegepant Using Neutral and Cationic Cobalt Precatalysts

The cobalt-catalyzed asymmetric hydrogenation of indazole-containing enamides relevant to the synthesis of the calcitonin gene-related peptide (CGRP) receptor antagonist, zavegepant (1), approved for the treatment of migraines, is described. Both neutral bis(phosphine)cobalt(II) and cationic bis(phosphine)cobalt(I) complexes served as efficient precatalysts for the enamide hydrogenation reactions, providing excellent yield and enantioselectivities (up to >99.9%) for a range of related substrates, though key reactivity differences were observed. Hydrogenation of indazole-containing enamide, methyl (Z)-2-acetamido-3-(7-methyl-1H-indazol-5-yl)acrylate, was performed on a 20 g scale.

Cobalt-Catalyzed Asymmetric Hydrogenation: Substrate Specificity and Mechanistic Variability

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area.

Cobalt-Catalyzed Efficient Asymmetric Hydrogenation of α-Primary Amino Ketones

Based on an amino-group-assisted coordination strategy and a proton-shuttle-activated outer-sphere mode, the cobalt-catalyzed asymmetric hydrogenation of α-primary amino ketones has been developed, resulting in the efficient synthesis of chiral vicinal amino alcohols bearing functionalized aryl rings in high yields and enantioselectivities (up to 99% enantiomeric excess (ee)) within 0.5 h.