Asymmetric Synthesis of Vabicaserin via Oxidative Multicomponent Annulation and Asymmetric Hydrogenation of a 3,4-Substituted Quinolinium Salt

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.

Exploration of chiral diastereomeric spiroketal (SPIROL)-based phosphinite ligands in asymmetric hydrogenation of heterocycles

New and readily available chiral SPIROL-based diphosphinite ligands (SPIRAPO) have been prepared and employed for iridium-catalyzed asymmetric hydrogenations of quinolines, quinoxalines and 2H-1,4-bezoxazin-2-ones. While the structurally similar (R,R,R)-SPIRAPO and (R)-SPINOL-based phosphinites were not the best ligands for these transformations, the (S,R,R)-diastereomer of SPIRAPO was found to be highly effective ligand for the reduction of 20 different heterocyclic systems with loadings as low as S/C = 10 000. This dearomatizative hydrogenation provided direct access to optically active tetrahydroquinolines in high enantioselectivities (up to 94% ee) and excellent yields (up to 99%), and was used to generate 1.75 g of natural alkaloid (-)-(R)-angustureine. This protocol was subsequently extended to achieve asymmetric hydrogenation of quinoxalines and 2H-1,4-benzoxazin-2-ones in good to excellent enantioselectivities.

Regioselective Opening of Nitroepoxides with Unsymmetrical Diamines

Nitroepoxides are easily transformed into benzodiazepines, tetrahydrobenzodiazepines, imidazopyridines, and N-alkyl tetrahydroquinoxalines by treatment with 2-aminobenzylamines, 2-aminopyridines, and N-alkyl 1,2-diaminobenzenes, respectively. Regioselectivity is controlled through attack of the most nucleophilic nitrogen of the unsymmetrical diamine to the β position of the epoxide. These reactions represent an efficient way to prepare privileged bioactive structures.

Modern advances in heterocyclic chemistry in drug discovery

New advances in synthetic methodologies that allow rapid access to a wide variety of functionalized heterocyclic compounds are of critical importance to the medicinal chemist as it provides the ability to expand the available drug-like chemical space and drive more efficient delivery of drug discovery programs. Furthermore, the development of robust synthetic routes that can readily generate bulk quantities of a desired compound help to accelerate the drug development process. While established synthetic methodologies are commonly utilized during the course of a drug discovery program, the development of innovative heterocyclic syntheses that allow for different bond forming strategies are having a significant impact in the pharmaceutical industry. This review will focus on recent applications of new methodologies in C-H activation, photoredox chemistry, borrowing hydrogen catalysis, multicomponent reactions, regio- and stereoselective syntheses, as well as other new, innovative general syntheses for the formation and functionalization of heterocycles that have helped drive project delivery. Additionally, the importance and value of collaborations between industry and academia in shaping the development of innovative synthetic approaches to functionalized heterocycles that are of greatest interest to the pharmaceutical industry will be highlighted.

β-Hydroxy-tetrahydroquinolines from Quinolines Using Chloroborane: Synthesis of the Peptidomimetic FISLE-412

A new synthetic protocol provides a simple and direct method to generate functionalized β-hydroxy-tetrahydroquinolines (THQs). Hydroboration of quinolines using chloroboranes followed by oxidation with NaBO3 ⋅H2 O led to the formation of functionalized β-hydroxy THQs. High regio- and diastereoselectivities were observed in α and γ substituted quinolines and the trans diastereomer of the β-hydroxy-THQ was the major isostere. This new protocol was utilized to build the novel antibody-targeted lupus peptidomimetic, FISLE-412.

A phosphine mediated sequential annulation process of 2-tosylaminochalcones with MBH carbonates to construct functionalized aza-benzobicyclo[4.3.0] derivatives

A novel phosphine mediated sequential annulation process to construct functionalized aza-benzobicyclo[4.3.0] derivatives has been developed involving a one-pot process.