Enantioselective Black rearrangement catalyzed by chiral bicyclic imidazole

Convergent Syntheses of Isomeric Imidazolospiroketones as Templates for Acetyl-CoA Carboxylase (ACC) Inhibitors

The synthesis of imidazole fused spirocyclic ketones as templates for acetyl-CoA carboxylase (ACC) inhibitors is reported. By completing the spirocyclic ring closure via divergent pathways, the synthesis of these regioisomers from common intermediates was developed. Through an aldehyde homologation/transmetalation strategy, one isomer was formed selectively. The second desired isomer was obtained via an intramolecular aromatic homolytic substitution reaction. Preparation of these isomeric spiroketones provided templates which, upon elaboration, led to key structure-activity relationship (SAR) points for delivery of potent ACC inhibitors.

Di-, tetra-, and perhydropyrrolo[1,2-a]imidazoles: The Methods of Synthesis and Some Aspects of Application

The review summarizes and systematizes the literature data on the synthesis and some aspects of application of pyrrolo[1,2-a]imidazoles. Synthetic approaches are grouped according to the degree of saturation of the product pyrroloimidazole ring. The bibliography of the review includes 110 sources over the last 15 years.

Cu-Catalyzed N-Arylation of Prolinamides: Access to Enantioenriched DMAP Analogues and Its Application in Black Rearrangement

A CuI-catalyzed C-N coupling reaction of 3-bromo-DMAP with l-prolinamides was conducted at 80 °C in 12-16 h, where the prolinamide's structure had an accelerating effect on the Ullmann-type reaction. This reaction was used to construct chiral 3-amino DMAP catalysts. Furthermore, enantioenriched DMAP analogue C8 was applied in an asymmetric Black rearrangement of 2-benzofuranylcarbonates, affording 3,3-disubstituted benzofuran-2-ones in up to 96% yield and 97% ee.

Catalytic Enantioselective Steglich-Type Rearrangement of Enol Lactones: Asymmetric Synthesis of Spirocyclic 1,3-Diketones

An example of asymmetric Steglich-type rearrangement of enol lactones is reported. This highly enantioselective acyl transfer reaction is catalyzed by chiral isothiourea at ambient temperature and provides a useful synthetic approach to access enantioenriched spirotricyclic β,β'-diketones from a broad range of indanone or tetralone-derived lactones. Preliminary mechanistic studies suggest the initial formation of an N-acylated iminium cation intermediate that induces a following facial selective condensation.

Design, Synthesis, and Application of Chiral Bicyclic Imidazole Catalysts

Asymmetric organocatalysis has been considered to be an efficient and reliable strategy for the stereoselective preparation of optically active chemicals. In particular, chiral tertiary amines as Lewis base organocatalysts bearing core structures including quinuclidine, dimethylaminopyridine (DMAP), N-methylimidazole (NMI), amidine, etc. have provided new and powerful tools for various chemical transformations. However, due to the limitations in structural complexity, synthetic difficulty, low catalytic efficiency, and high cost, the industrial application of such catalysts is still far from being widely adopted. Therefore, the development of new chiral tertiary amine catalysts with higher activity and selectivity is greatly desired.In order to address the contradiction between activity and selectivity caused by the ortho group, a bicyclic imidazole structure bearing a relatively large bond angle ∠θ was designed as the skeleton of our new catalysts. 6,7-Dihydro-5H-pyrrolo[1,2-a]imidazole (abbreviated as DPI) and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine (abbreviated as TIP) are two of the utilized skeletons. In addition to obtaining satisfactory catalytic activity, excellent enantioselectivity would also be expected because the stereocontrol R group is neither far nor close to the catalytic active site (sp²-N atom) and is adjustable. Based on this skeleton, a family of chiral bicyclic imidazole catalysts were easily prepared and successfully applied in several enantioselective reactions for the synthesis of a variety of valuable chiral compounds.6,7-Dihydro-5H-pyrrolo[1,2-a]imidazole (abbreviated as DPI) is the predominantly utilized skeleton. First, HO-DPI, the key intermediate of the designed chiral bicyclic imidazole catalysts, could be efficiently synthesized from imidazole and acrolein, then separated by kinetic resolution or optical resolution. Second, Alkoxy-DPI, the alkyloxy-substituted chiral bicyclic imidazole catalysts, were synthesized by a one-step alkylation from HO-DPI. This type of catalyst has been successfully applied in asymmetric Steglich rearrangement (C-acylation rearrangement of O-acylated azlactones), asymmetric phosphorylation of lactams, and a sequential four-step acylation reaction. Third, Acyloxy-DPI, the acyloxy-substituted chiral bicyclic imidazole catalysts, were synthesized with a one-step acetylative kinetic resolution from racemic HO-DPI or acylation from enantiopure HO-DPI. The catalyst AcO-DPI has been successfully applied in enantioselective Black rearrangement and in direct enantioselective C-acylation of 3-substituted benzofuran-2(3H)-ones and 2-oxindoles. Fourth, Alkyl-DPI was synthesized via a two-step reaction from racemic HO-DPI and separated easily by resolution. The catalyst Cy-DPI has been successfully applied in dynamic kinetic resolution of 3-hydroxyphthalides through enantioselective O-acylation. Cy-PDPI was synthesized through a Cu-catalyzed amidation from Cy-DPI and successfully applied in the kinetic resolution of secondary alcohols with good to excellent enantioselectivities. Finally, the carbamate type chiral bicyclic imidazole catalysts, Carbamate-DPI, were readily synthesized from HO-DPI, and the catalyst Ad-DPI bearing a bulky adamantyl group was successfully applied in the synthesis of the anti-COVID-19 drug remdesivir via asymmetric phosphorylation. Alongside our initial work, this Account also introduces four elegant studies by other groups concerning asymmetric phosphorylation utilizing chiral bicyclic imidazole catalysts.In summary, this Account focuses on the chiral bicyclic imidazole catalysts developed in our group and provides an overview on their design, synthesis, and application that will serve as inspiration for the exploration of new organocatalysts and related reactions.

Recent advances in catalytic asymmetric [1,3]-rearrangement reactions

This review covering the recent advances of asymmetric 1,3-rearrangement reactions is divided into four different fields, including transition metal catalysis, nucleophilic catalysis, Brønsted acid catalysis and Lewis acid catalysis.

Chemical Synthesis of the Anti-COVID-19 Drug Remdesivir

Remdesivir has become an important compound for the treatment of COVID‐19. Here, we describe the catalytic asymmetric synthesis of this anti‐COVID‐19 drug. First, the P‐racemic phosphoryl chloride is synthesized in a facile procedure. Then, it is possible to obtain the protected remdesivir via the organocatalytic asymmetric phosphorylation of protected nucleoside GS441524 with P‐racemic phosphoryl chloride catalyzed by chiral bicyclic imidazole. Finally, remdesivir is easily prepared by deprotection. © 2021 Wiley Periodicals LLC.

Basic Protocol 1: Synthesis of 2‐ethylbutyl (chloro(phenoxy)phosphoryl)‐l‐alaninate rac‐4

Basic Protocol 2: Synthesis of chiral bicyclic imidazole Ad‐DPI

Basic Protocol 3: Synthesis of remdesivir

Efficient synthesis of antiviral agent uprifosbuvir enabled by new synthetic methods

An efficient route to the HCV antiviral agent uprifosbuvir was developed in 5 steps from readily available uridine in 50% overall yield. This concise synthesis was achieved by development of several synthetic methods: (1) complexation-driven selective acyl migration/oxidation; (2) BSA-mediated cyclization to anhydrouridine; (3) hydrochlorination using FeCl₃/TMDSO; (4) dynamic stereoselective phosphoramidation using a chiral nucleophilic catalyst. The new route improves the yield of uprifosbuvir 50-fold over the previous manufacturing process and expands the tool set available for synthesis of antiviral nucleotides.

An efficient route to the HCV antiviral agent uprifosbuvir was developed in 5 steps from readily available uridine in 50% overall yield.

Catalytic Asymmetric Synthesis of the anti-COVID-19 Drug Remdesivir

The catalytic asymmetric synthesis of the anti-COVID-19 drug Remdesivir has been realized by the coupling of the P-racemic phosphoryl chloride with protected nucleoside GS441524. The chiral bicyclic imidazole catalyst used is crucial for the dynamic kinetic asymmetric transformation (DyKAT) to proceed smoothly with high reactivity and excellent stereoselectivity (96 % conv., 22:1 S_P :R_P ). Mechanistic studies showed that this DyKAT is a first-order visual kinetic reaction dependent on the catalyst concentration. The unique chiral bicyclic imidazole skeleton and carbamate substituent of the catalyst are both required for the racemization process, involving the phosphoryl chloride, and subsequent stereodiscriminating step. A 10 gram scale reaction was also conducted with comparably excellent results, showing its potential for industrial application.

Chiral Fe(ii) complex catalyzed enantioselective [1,3] O-to-C rearrangement of alkyl vinyl ethers and synthesis of chromanols and beyond

A highly efficient enantioselective [1,3] O-to-C rearrangement of racemic vinyl ethers that operates under mild conditions was developed. This method with chiral ferrous complex catalyst provided an efficient access to a wide range of chromanols with high yields and excellent enantioselectivities. In addition, an important urological drug (R)-tolterodine and others were easily obtained after simple transformations.

A step-economic and one-pot access to chiral Cα-tetrasubstituted α-amino acid derivatives via a bicyclic imidazole-catalyzed direct enantioselective C-acylation

C^α-Tetrasubstituted α-amino acids are ubiquitous and unique structural units in bioactive natural products and pharmaceutical compounds. The asymmetric synthesis of these molecules has attracted a lot of attention, but a more efficient method is still greatly desired. Here we describe the first sequential four-step acylation reaction for the efficient synthesis of chiral C^α-tetrasubstituted α-amino acid derivatives from simple N-acylated amino acids via an auto-tandem catalysis using a single nucleophilic catalyst. The synthetic efficiency is improved via a direct enantioselective C-acylation; the methodology affords the corresponding C^α-tetrasubstituted α-amino acid derivatives with excellent enantioselectivities (up to 99% ee). This step-economic, one-pot, and auto-tandem strategy provides facile access to important chiral building blocks, such as peptides, serines, and oxazolines, which are often used in medicinal and synthetic chemistry.

The first four-step sequential reaction for the synthesis of C^α-tetrasubstituted chiral α-amino acid derivatives via auto-tandem catalysis has been developed.

Development of a new bicyclic imidazole nucleophilic organocatalyst for direct enantioselective C-acylation

A new chiral nucleophilic organocatalyst bearing a 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine skeleton has been developed.

A novel chiral DMAP–thiourea bifunctional catalyst catalyzed enantioselective Steglich and Black rearrangement reactions

A novel chiral DMAP–thiourea bifunctional catalyst has been prepared and applied in the highly enantioselective Steglich and Black rearrangement reactions.

Enantioselective rearrangement of indolyl carbonates catalyzed by chiral DMAP-N-oxides

Bifunctional chiral DMAP-N-oxides, which utilize the oxygen atom as a nucleophilic site, have been reported for the highly enantioselective rearrangement of indolyl carbonates.

Direct enantioselective C-acylation for the construction of a quaternary stereocenter catalyzed by a chiral bicyclic imidazole

A direct enantioselective C-acylation of benzofuranones was developed using a chiral bicyclic imidazole catalyst and an achiral tertiary amine additive.

Ni-Catalyzed Enantioselective C-Acylation of α-Substituted Lactams

A new strategy for catalytic enantioselective C-acylation to generate α-quaternary-substituted lactams is reported. Ni-catalyzed three-component coupling of lactam enolates, benzonitriles, and aryl halides produces β-imino lactams that then afford β-keto lactams by acid hydrolysis. Use of a readily available Mandyphos-type ligand and addition of LiBr enable the construction of quaternary stereocenters on α-substituted lactams to form β-keto lactams in up to 94% ee.