Asymmetric hydrogen transfer reactions promoted by homogeneous transition metal catalysts

Enantioselective Synthesis of Alcohols and Amines by Iridium‐Catalyzed Hydrogenation, Transfer Hydrogenation, and Related Processes

“…[4] Nonetheless, recent developments have demonstrated the great potential of chiral iridium complexes also as catalysts for ketone reductions. [3] As expected, many of the catalytic systems based on iridium have drawn inspiration from ruthenium and rhodium analogues. An array of chiral ligands have been combined with Ir I and Ir III precursors to provide efficient catalysts for both ATH and AH of ketones.…”

“…[3] Much effort has been devoted to the design and synthesis of ligands and the catalytic efficiency has been evaluated, in particular, with Ru, Rh, Ir, and recently also Fe complexes. [98] In 1995, Noyori, Ikariya, and co-workers reported the first example of what has become the most notable type of catalysts used in the ATH of ketones: Ruthenium complexes with monotosylated diamines, such as [ Figure 1, left) were able to reduce simple ketones into chiral alcohols with exceptional efficiency.…”

“…Selected examples from early contributions to the latest achievements are discussed. [3] Iridium-catalyzed asymmetric transfer hydrogenation of ketones Early reports: The first example of iridium-catalyzed TH (transfer hydrogenation) was reported already in 1967 by Henbest. [107] It took several more years for the first ATH reports using iridium catalysis to appear.…”

“…Our intention is to give the reader an overview of the results obtained in the area, and to highlight successful examples for which iridium complexes have been used in asymmetric reductions of carbonyls and imines, and in related processes. [1][2][3][4] We have chosen pioneering reports and the most outstanding examples in terms of high enantioselectiviy, high turnover number (TON), and frequency (TOF), mild conditions (i.e., reactivity at low hydrogen pressures), and hydrogenation of challenging substrates. The review examines literature up to December 2012, with the aim of complementing some of the existing excellent reviews reported on this matter.…”

Synthetic Route to Novel Asymmetric Tetradentate Ligands Containing Both Amino and Imino Groups

“…To achieve this, a careful design of the ligand is necessary. In this connection, unsymmetrical ligands are also required to imitate many of the active sites of the metalloproteins [4][5][6].…”