Synthesis of Chiral 1,2-Amino Alcohol-Containing Compounds Utilizing Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of Unprotected α-Ketoamines.

Herein, we disclose a facile synthetic strategy to access an important class of drug molecules that contain chiral 1,2-amino alcohol functionality utilizing highly effective ruthenium-catalyzed asymmetric transfer hydrogenation of unprotected α-ketoamines. Recently, the COVID-19 pandemic has caused a crisis of shortage of many important drugs, especially norepinephrine and epinephrine, for the treatment of anaphylaxis and hypotension because of the increased demand. Unfortunately, the existing technologies are not fulfilling the worldwide requirement due to the existing lengthy synthetic protocols that require additional protection and deprotection steps.

DFT investigation of coupling constant anomalies in substituted β-lactams.

β-lactams are a chemically diverse group of molecules with a wide range of biological activities. Having recently observed curious trends in J coupling values in studies on this structural class, we sought to obtain a more comprehensive understanding of these diagnostic NMR parameters, specifically interrogating J, J, and J, to differentiate 3- and 4-monosubstituted β-lactams. Further investigation using computational chemistry methods was employed to explore the geometric and electronic origins for the observed and calculated differences between the two substitution patterns.

Application of Chiral Transfer Reagents to Improve Stereoselectivity and Yields in the Synthesis of the Antituberculosis Drug Bedaquiline.

Bedaquiline (BDQ) is an important drug for treating multidrug-resistant tuberculosis (MDR-TB), a worldwide disease that causes more than 1.6 million deaths yearly. The current synthetic strategy adopted by the manufacturers to assemble this molecule relies on a nucleophilic addition reaction of a quinoline fragment to a ketone, but it suffers from low conversion and no stereoselectivity, which subsequently increases the cost of manufacturing BDQ.

Design and Discovery of Water-Soluble Benzooxaphosphole-Based Ligands for Hindered Suzuki-Miyaura Coupling Reactions with Low Catalyst Load.

We report a new class of highly effective, benzooxaphosphole-based, water-soluble ligands in the application of Suzuki-Miyaura cross-coupling reactions for sterically hindered substrates in aqueous media. The catalytic activities of the coupling reactions were greatly enhanced by the addition of catalytic amounts of organic phase transfer reagents, such as tetraglyme and tetrabutylammonium bromide. The optimized general protocol can be conducted with a low catalyst load, thereby providing a practical solution for these reactions.

A Practical Method for the Large-Scale Preparation of the -Chiral Dihydrobenzoazaphosphole Core by Chemical Resolution.

ZPhos, as an effective ligand in the Cu-catalyzed asymmetric hydrogenation of ketones and aminoboration of alkenes, is prepared efficiently from the corresponding triflate of -chiral dihydrobenzoazaphosphole . However, the previous approach to by chiral separation is time-consuming and costly, preventing its production and further application on a large scale. In this report, a practical method for the large-scale preparation of was developed via chiral chemical resolution with (1,2)-diaminocyclohexane as an effective resolution reagent.

Facile and Scalable Methodology for the Pyrrolo[2,1-][1,2,4]triazine of Remdesivir.

Pyrrolo[2,1-][1,2,4]triazine () is an important regulatory starting material in the production of the antiviral drug remdesivir. Compound was produced through a newly developed synthetic methodology utilizing simple building blocks such as pyrrole, chloramine, and formamidine acetate by examining the mechanistic pathway for the process optimization exercise. Triazine was obtained in 55% overall yield in a two-vessel-operated process.

Carbamoyl Anion Addition to Azirines.

The addition of carbamoyl anions to azirines affords synthetically useful 2-aziridinyl amide building blocks. The reaction scope was explored with respect to both formamide and azirine, and the addition was found to be highly diastereoselective. A one-pot conversion of a ketoxime to an aziridinyl amide was demonstrated.

A Noncoordinating Acid-Base Catalyst for the Mild and Nonreversible -Butylation of Alcohols and Phenols.

A mild and nonreversible -butylation of alcohols and phenols can be achieved in high yields using the noncoordinating acid-base catalyst [bis(trifluoromethane)sulfonimide and 2,6-lutidine] with a -butylation reagent, -butyl 2,2,2-trichloroacetimidate. This method allows the use of substrates containing acid sensitive groups such as ketal, Boc, and boronate esters.

Atom-Economical Cross-Coupling of Internal and Terminal Alkynes to Access 1,3-Enynes.

Selective carbon-carbon (C-C) bond formation in chemical synthesis generally requires prefunctionalized building blocks. However, the requisite prefunctionalization steps undermine the overall efficiency of synthetic sequences that rely on such reactions, which is particularly problematic in large-scale applications, such as in the commercial production of pharmaceuticals. Herein, we describe a selective and catalytic method for synthesizing 1,3-enynes without prefunctionalized building blocks.

Rational Design of New Dihydrobenzooxophosphole-Based Lewis Base Organocatalysts.

A series of new dihydrobenzooxophosphole-based Lewis Base organocatalysts were designed and synthesized. They are demonstrated effective in trichlorosilane-mediated stereoselective conjugate reductions of C=C bonds. DFT calculations reveal that the strong hydrogen bond between the amide linker and the chloride on silicon in the transition state contributes to the high reactivity of the catalyst .

Sulfone-Mediated SAr Reaction as a Powerful Tool for the Synthesis of 4-Quinolinyl Ethers and More-Application to the Synthesis of HCV NS3/4a Protease Inhibitor .

An efficient general methodology for the synthesis of 4-quinolinyl ethers is demonstrated via a highly reactive SAr reaction of 4-quinolinyl sulfones with a range of structurally diversified 1°, 2°, and 3° alcohols with a wide substrate scope and high yields. By adapting this methodology, a convergent synthesis of a complex target of HCV NS3/4a protease inhibitor was accomplished.

Nickel-Catalyzed Cross-Electrophile Reductive Couplings of Neopentyl Bromides with Aryl Bromides.

5-Cyanoimidazole was identified as an inexpensive ligand for nickel-catalyzed cross-electrophile couplings by screening a diverse set of pharmaceutical compound library. A strategic screening approach led to the discovery of this novel ligand, which was successfully applied in the preparation of various alkylated arene products with good to high yields. Furthermore, the properties of this ligand allowed expanding the scope of reductive couplings to challenging substrates, such as sterically hindered neopentyl halides, which are known to generate motifs that are prevalent in biologically active molecules.

Cu-Catalyzed Asymmetric Aminoboration of -Vinylarenes with ZPhos as the Ligand.

A Cu-catalyzed enantioselective aminoboration of -vinylarenes with ZPhos as a ligand is reported. Enantioenriched aminoborates are prepared with excellent regio- and enantioselectivities up to >99:1 er under the optimized conditions. The utility of the current method was further established by rapid conversion of an adduct to a chiral benzo[][1,4]oxazepine.

Asymmetric Library Synthesis of P-Chiral t-Butyl-Substituted Secondary and Tertiary Phosphine Oxides.

An asymmetric synthesis, amenable to library preparation of structurally diverse P-chiral t-butyl substituted secondary phosphine oxides (SPOs) and tertiary phosphine oxides (TPOs), was developed. A P-chiral H-phosphinate building block was prepared via a two-step, one-pot condensation of a chiral auxiliary with t-BuPCl, followed by hydrolysis. Nucleophilic displacement of the chiral auxiliary with Grignard reagents, followed by hydrolysis, provided a library of P-chiral SPOs.

P-Chiral Phosphorus Ligands Based on a 2,3-Dihydrobenzo[ d][1,3]oxaphosphole Motif for Asymmetric Catalysis.

Despite the rapid progress in the field of asymmetric catalysis, the search for new, efficient, and practical asymmetric catalytic transformations to facilitate the green synthesis of chiral natural products and drugs will continue to be a major ongoing effort in organic chemistry. Chiral phosphorus ligands have played a significant role in recent advances in transition-metal-catalyzed asymmetric transformations. However, there remain numerous challenging issues of reactivity and selectivity in catalysis.

Enantioselective Synthesis of 4-Methyl-3,4-dihydroisocoumarin via Asymmetric Hydroformylation of Styrene Derivatives.

Enantioenriched aldehydes are produced through asymmetric hydroformylation of styrene derivatives using BIBOP-type ligands. The featured example is enantioselective synthesis of 4-methyl-3,4-dihydroisocoumarin, which was prepared in a 95.1:4.

Application of a Preformed Pd-BIDIME Precatalyst to Suzuki-Miyaura Cross-Coupling Reaction in Flow.

The application of a Buchwald's third generation palladacycle containing a dihydrobenzooxaphosphole-based ligand (e.g., BIDIME) was reported in the Suzuki cross-coupling reaction.

Synthesis of highly potent lymphocyte function-associated antigen-1 antagonists labeled with carbon-14 and with stable isotopes, part 3.

The drug candidates (2) and (3) are highly potent LFA-1 inhibitors. They were efficiently prepared labeled with carbon-14 using a palladium-catalyzed carboxylation of an iodo-precursor (5) and sodium formate- C to afford acid [ C]-(6), which was coupled via an amide bond to chiral amines (7) and (8) in 52% and 48% overall yield, respectively, and with specific activities higher than 56 mCi/mmol and radiochemical purities of 99%. For stable isotopes synthesis, the amine [ H ]-(7) was synthesized in three steps from 2-cyanopyridine- H using Kulinkovich-Szymonik aminocyclopropanation, followed by coupling to L-alanine-2,3,3,3- H -N-t-BOC, and then removal of the BOC-protecting group.

Computationally Assisted Mechanistic Investigation and Development of Pd-Catalyzed Asymmetric Suzuki-Miyaura and Negishi Cross-Coupling Reactions for Tetra-Substituted Biaryl Synthesis.

Metal-catalyzed cross-coupling reactions are extensively employed in both academia and industry for the synthesis of biaryl derivatives for applications to both medicine and material science. Application of these methods to prepare tetra--substituted biaryls leads to chiral atropisomeric products that introduces the opportunity to use catalyst-control to develop asymmetric cross-coupling procedures to access these important compounds. Asymmetric Pd-catalyzed Suzuki-Miyaura and Negishi cross-coupling reactions to form tetra--substituted biaryls were studied employing a collection of -chiral dihydrobenzooxaphosphole (BOP) and dihydrobenzoazaphosphole (BAP) ligands.

Copper-catalyzed asymmetric hydrogenation of 2-substituted ketones dynamic kinetic resolution.

A new class of tunable heterophosphole dimeric ligands have been designed and synthesized. These ligands have enabled the first examples of Cu-catalyzed hydrogenation of 2-substituted-1-tetralones and related heteroaryl ketones dynamic kinetic resolution, simultaneously creating two contiguous stereogenic centers with up to >99 : 1 dr and 98 : 2 er. The ligand-Cu complexes were isolated and characterized by single crystal X-ray, and DFT calculations revealed a novel heteroligated dimeric copper hydride transition state.

Potent and selective CC chemokine receptor 1 antagonists labeled with carbon-13, carbon-14, and tritium.

1-(4-Fluorophenyl)-1H-pyrazolo[3,4-c]pyridine-4-carboxylic acid (2-methanesulfonyl-pyridin-4-ylmethyl)-amide (1) and its analogs (2) and (3) are potent CCR1 antagonists intended for the treatment of rheumatoid arthritis. The detailed syntheses of these 3 compounds labeled with carbon-13 as well as the preparation of (1) and (2) labeled with carbon-14, and (1) labeled with tritium, are described.

BABIPhos Family of Biaryl Dihydrobenzooxaphosphole Ligands for Asymmetric Hydrogenation.

Novel bidentate phosphine ligands BABIPhos featuring a biaryl bis-dihydrobenzooxaphosphole core are presented. Their synthesis was achieved via Pd-catalyzed reductive homocoupling of dihydrobenzooxaphosphole aryl triflates. An efficient route toward various analogues was also established, giving access to phosphines with different electronic and steric properties.

Ligand-Enabled γ-C(sp)-H Activation of Ketones.

We report the first example of Pd(II)-catalyzed γ-C(sp)-H activation of ketones directed by a practical 2,2-dimethyl aminooxyacetic acid auxiliary. 2-Pyridone ligands are identified to enable C(sp)-H activation for the first time. A rare six-membered palladacycle intermediate is isolated and characterized to elucidate the reaction mechanism.

Enantioselective Synthesis of α-(Hetero)aryl Piperidines through Asymmetric Hydrogenation of Pyridinium Salts and Its Mechanistic Insights.

Enantioselective synthesis of α-aryl and α-heteroaryl piperidines is reported. The key step is an iridium-catalyzed asymmetric hydrogenation of substituted N-benzylpyridinium salts. High levels of enantioselectivity up to 99.