Ruthenium‐Catalyzed Enantioselective Hydrogenation of 9‐Phenanthrols

Abstract

The enantioselective hydrogenation of arenols to corresponding chiral cyclic alcohols remains a challenge because of their aromaticity and the difficulty in controlling the regio‐, chemo‐, and stereoselectivity. In this work, the first highly efficient ruthenium‐catalyzed enantioselective hydrogenation of 9‐phenanthrols has been successfully realized under mild conditions via trapping the unstable keto tautomers. The method provides a facile access to a range of chiral 9,10‐dihydrophenanthren‐9‐ols with up to 98 % yield and >99 % ee. The hydrogenation pathway includes base‐promoted tautomerization of 9‐phenanthrols and Ru‐catalyzed asymmetric hydrogenation of the in situ generated unstable keto tautomers.

Visible-Light-Promoted 6π Photocyclization of ortho-Biaryl-Appended β-Ketoesters

“…5 Very recently, an elegant Ru-catalyzed asymmetric hydrogenation of the 9-phenanthrols for the direct synthesis of the chiral 9,10-dihydrophenanthren-9-ols was reported by Fan and Feng et al, but their substrates failed to produce substrates bearing electron-withdrawing substituents (Scheme 1C). 6 Despite the progress achieved in the synthesis of 9,10-dihydrophenanthren-9-ols, most of the existing methods require harsh reaction conditions, and extra superstoichiometric reductants and additives. Thus, the development of a mild and convenient approach to the direct construction of 9,10-dihydrophenanthren-9-ol analogues is highly desirable.…”

“…In 2021, Song and Wang reported a domino intramolecular [3 + 2] cycloaddition and ring-opening aromatization process between dialdehyde compounds and trans -4-hydroxy- l -proline or indoline-2-carboxylic acid for the efficient direct synthesis of substituted 9,10-dihydrophenanthren-9-ols (Scheme B) . Very recently, an elegant Ru-catalyzed asymmetric hydrogenation of the 9-phenanthrols for the direct synthesis of the chiral 9,10-dihydrophenanthren-9-ols was reported by Fan and Feng et al, but their substrates failed to produce substrates bearing electron-withdrawing substituents (Scheme C) . Despite the progress achieved in the synthesis of 9,10-dihydrophenanthren-9-ols, most of the existing methods require harsh reaction conditions, and extra superstoichiometric reductants and additives.…”

Low Onset‐Potential Z‐Scheme Ta3N5‐based Photoanode with Enhanced Light Harvesting and Charge Transport

“…To achieve low V on , Ta 3 N 5 photoanodes have implemented various strategies to increase V ph and decrease overpotential simultaneously. For instance, functional layers serving as charge transport (GaN, [ 14 ] NbN x [ 15 ] ), surface passivation (AlO x , [ 16 ] TiO x [ 17 ] ), and hole storage (Fh [ 18 ] ) can further increase V ph by boosting charge separation efficiency. Furthermore, OEC modifications, such as NiFeO x , [ 19 ] NiCoFe‐B i , [ 20 ] and Co(OH) 2 , [ 21 ] effectively reduce the overpotential by providing abundant catalytic active sites and prolonging hole lifetimes.…”

Ru-NHC-Catalyzed Asymmetric, Complete Hydrogenation of Indoles and Benzofurans: One Catalyst with Dual Function

“…The transformation and utilization of inexpensive and readily available arenes have become a principal area of research. − The complete hydrogenation of arenes − is one of the most effective methods for converting planar molecules into saturated three-dimensional structures, which are critical building blocks in many aspects of life. ,− However, asymmetric hydrogenation of arenes has historically been a major challenge due to the lack of enantioselective catalysts, and the successful cases have largely been confined to the rings with weak aromaticity, such as heteroaromatic rings ,− and fused arenes. − The combination of heterogeneous and homogeneous catalysis has proven to be a promising method for hydrogenation of aromatic compounds. − Recently, Andersson’s group utilized an excessive amount of ligands compared to the Rh precursor to generate both homo- and heterogeneous catalysts in the reaction. Subsequently, they took advantage of the high reaction rate of homogeneous hydrogenation and the induction period of heterogeneous hydrogenation to achieve an asymmetric and complete reduction of arenes (Figure a) .…”