Enantioselective Hydrogenation of Racemic α-Arylamino Lactones to Chiral Amino Diols with Site-Specifically Modified Chiral Spiro Iridium Catalysts

Abstract

A protocol for highly enantioselective hydrogenation of racemic α-arylamino lactones with catalysis by site-specifically modified chiral spiro iridium complexes has been developed. With the optimized catalyst, racemic α-arylamino-γ-lactones and α-arylamino-δ-lactones could be hydrogenated to the corresponding chiral 2-amino diols with good to excellent enantioselectivities.

CuH-Catalyzed Atropoenantioselective Reduction of Bringmann’s Lactones via Dynamic Kinetic Resolution

“…In light of the precedence of CuH toward reduction of aryl lactones, we envisaged that asymmetric CuH catalysis would be a suitable choice to enable dynamically kinetic reduction of Bringmann’s lactones (Scheme ). A challenge is, however, anticipated since the reduction of esters with a chiral metal catalyst especially chiral CuH remains underdeveloped …”

Bifunctional Homogeneous Catalysts Based on Ruthenium, Rhodium and Iridium in Asymmetric Hydrogenation

“…AH of ketones, lactones and -ketoesters using an iridium catalyst based on a P(NH)N spiro ligand by Zhou, Xie and co-workers. [219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234] This method provides one of the most impressive recent applications of Ir-bifunctional catalysts in asymmetric hydrogenation, in terms of both catalytic efficiency, enantioselectivity, substrate scope and synthetic potential. It is worth to note that Zhang, Yin and co-workers reported in parallel the synthesis of rather similar oxaspirocyclic chiral ligands and applied them to iridium-catalyzed direct asymmetric hydrogenation of Bringmann's lactones (Scheme 73a).…”

“…[225][226][227][228][229][230][231][232] A recent application to the AH/Dynamic kinetic resolution of racemic α-arylamino-γ-lactones and α-arylamino-δlactones led to the corresponding chiral 2-amino diols with high yields and enantioselectivities (Scheme 72d). [233][234] According to theoretical studies, the hydride and proton transfer step proceeds via a cyclic 6membered transition state. The calculated transition state of lowest energy leads to the (S)-2-amino-diol, as observed experimentally.…”

Chiral Tridentate Ligands in Transition Metal-Catalyzed Asymmetric Hydrogenation

“…The corresponding chiral alcohols are important intermediates for the pharmaceutical industry and preparation of natural products. Apart from hydrogenation, PNN-Ir-1 was also efficient on kinetic resolution (KR) and dynamic kinetic resolution (DKR) − to form one or multiple chiral centers (Scheme ).…”