Iridium catalyzed asymmetric hydrogenation of cyclic imines of benzodiazepinones and benzodiazepines

Recent Advances in the Enantioselective Synthesis of Chiral Amines via Transition Metal-Catalyzed Asymmetric Hydrogenation

Chiral amines are key structural motifs present in a wide variety of natural products, drugs, and other biologically active compounds. During the past decade, significant advances have been made with respect to the enantioselective synthesis of chiral amines, many of them based on catalytic asymmetric hydrogenation (AH). The present review covers the use of AH in the synthesis of chiral amines bearing a stereogenic center either in the α, β, or γ position with respect to the nitrogen atom, reported from 2010 to 2020. Therefore, we provide an overview of the recent advances in the AH of imines, enamides, enamines, allyl amines, and N-heteroaromatic compounds.

Asymmetric three-component reaction of diazo compound with alcohol and seven-membered imine

A dirhodium and chiral phosphoric acid co-catalyzed asymmetric three-component reaction of diazo compound with alcohol and seven-membered imine has been developed via Mannich-type interception of transient oxonium ylide. This reaction...

Iron(III) Chloride as a Mild Catalyst for the Dearomatizing Cyclization of N-Acylindoles

A catalytic approach for the preparation of indolines by dearomatizing cyclization is presented. FeCl₃ acts as a catalyst to afford tetracyclic 5a,6-dihydro-12H-indolo[2,1-b][1,3]benzoxazin-12-ones in good yields. The cyclization also proceeds with tosylamides forming C-N bonds in 53% yield.

Organocatalytic asymmetric synthesis of benzazepinoindole derivatives with trifluoromethylated quaternary stereocenters by chiral phosphoric acid catalysts

An enantioselective aza-Friedel-Crafts reaction of trifluoromethyl dihydrobenzoazepinoindoles with pyrroles catalyzed by a chiral spirocyclic phosphoric acid was developed. This methodology provides a facile route to CF₃- and pyrrole-containing benzazepinoindoles bearing quaternary stereocenters in good yields and with moderate to excellent enantioselectivities (up to 93% ee). Indoles were also investigated as electron-rich aromatic substrates to afford the corresponding chiral heterocycles with good yields and considerable enantioselectivities. The introduction of CF₃ shows a remarkable fluorine effect and increases the activation and stereoinduction.

Iridium-catalyzed asymmetric hydrogenation of quinazolinones

Herein, we reported iridium-catalyzed asymmetric hydrogenation of quinazolinones with up to 98% ee and excellent yields.

Synthesis of chiral seven-membered cyclic sulfonamides through palladium-catalyzed arylation of cyclic imines

An enantioselective palladium-catalyzed addition of arylboronic acids to seven-membered cyclic N-sulfonyl aldimines and ketimines has been developed, giving the chiral cyclic sulfonamides with excellent yields and up to 99% ee.

Enantioselective synthesis of tunable chiral pyridine–aminophosphine ligands and their applications in asymmetric hydrogenation

A small library of tunable chiral pyridine–aminophosphine ligands were synthesized based on tetrahydroquinoline scaffolds obtained via Ru-catalyzed asymmetric hydrogenation. The ligands were applied in the Ir-catalyzed asymmetric hydrogenation of olefins and imines.

Access to Chiral Seven-Member Cyclic Amines via Rh-Catalyzed Asymmetric Hydrogenation

A highly efficient asymmetric hydrogenation of azepine/oxazepine-type seven-member cyclic imine hydrochlorides was successfully developed using Rh/bisphosphine-thiourea ligand ZhaoPhos, affording various chiral seven-member cyclic amines with full conversions, high yields, and excellent enantioselectivities (up to 96% yield, >99% ee). Additionally, this asymmetric hydrogenation can proceed well on gram scale with excellent ee value. Moreover, control experimental results displayed that the anion-bonding interaction between the chloride ion of the substrate and thiourea motif of the ZhaoPhos played an important role to obtain excellent enantioselectivity.

Ru-Catalyzed asymmetric transfer hydrogenation of substituted dibenzo[b,f][1,4]oxazepines in water

A phosphine free, additive free catalytic ATH protocol of dibenzo[b,f][1,4]oxazepine compounds using an (R,R)-Ru-Ts-DPEN complex was developed for the first time using HCOOH–HCOONa as a green hydrogen source.

An Update on the Synthesis of Pyrrolo[1,4]benzodiazepines

Pyrrolo[1,4]benzodiazepines are tricyclic compounds that are considered “privileged structures” since they possess a wide range of biological activities. The first encounter with these molecules was the isolation of anthramycin from cultures of Streptomyces, followed by determination of the X-ray crystal structure of the molecule and a study of its interaction with DNA. This opened up an intensive synthetic and biological study of the pyrrolo[2,1-c][1,4]benzodiazepines that has culminated in the development of the dimer SJG-136, at present in Phase II clinical trials. The synthetic efforts have brought to light some new synthetic methodology, while the contemporary work is focused on building trimeric pyrrolo[2,1-c][1,4]benzodiazepines linked together by various heterocyclic and aliphatic chains. It is the broad spectrum of biological activities of pyrrolo[1,2-a][1,4]benzodiazepines that has maintained the interest of researchers to date whereas several derivatives of the even less studied pyrrolo[1,2-d][1,4]benzodiazepines were found to be potent non-nucleoside HIV-1 reverse transcriptase inhibitors. The present review is an update on the synthesis of pyrrolo[2,1-c][1,4]benzodiazepines since the last major review of 2011, while the overview of the synthesis of the other two tricyclic isomers is comprehensive.

Chiral phosphine-phosphoramidite ligands for highly enantioselective hydrogenation of N-arylimines

The asymmetric hydrogenation of N-arylimines with the chiral phosphine-phosphoramidite ligand, (Sc,Sa)-PEAPhos 2b, has been developed, in which high turnover numbers and excellent enantioselectivity were achieved.

Iridium-catalyzed asymmetric hydrogenation of dibenzo[b,f][1,4]thiazepines

Highly enantioselective hydrogenation of substituted dibenzo[b,f][1,4]thiazepines was achieved with up to 96 % ee (enantiomeric excess) using [Ir(COD)Cl]2/(R)-SynPhos complex as catalyst in the presence of iodine. This method provides an efficient access to optically active 11-substituted-10,11-dihydrodibenzo[b,f][1,4]thiazepines.