An air- and moisture-stable ruthenium precatalyst for diverse reactivity.

Versatile, efficient and robust (pre)catalysts are pivotal in accelerating the discovery and optimization of chemical reactions, shaping diverse synthetic fields such as cross-coupling, C-H functionalization and polymer chemistry. Yet, their scarcity in certain domains has hindered the advancement and adoption of new applications. Here we present a highly reactive air- and moisture-stable ruthenium precatalyst [(tBuCN)5Ru(H2O)](BF4)2, featuring a key exchangeable water ligand. This versatile precatalyst drives an array of transformations, including late-stage C(sp2)-H arylation, primary/secondary alkylation, methylation, hydrogen/deuterium exchange, C(sp3)-H oxidation, alkene isomerization and oxidative cleavage, consistently outperforming conventionally used ruthenium (pre)catalysts. The generality and applicability of this precatalyst is exemplified through the potential for rapid screening and optimization of photocatalytic reactions with a suite of in situ generated ruthenium photocatalysts containing hitherto unknown complexes, and through the rapid discovery of reactivities previously unreported for ruthenium. The diverse applicability observed is suggestive of a generic platform for reaction simplification and accelerated synthetic discovery that will enable broader applicability and accessibility to state-of-the-art ruthenium catalysis.

Improving the sustainability of the ruthenium-catalysed N-directed C-H arylation of arenes with aryl halides.

Direct C-H functionalisation methodologies represent an opportunity to improve the overall 'green' credentials of organic coupling reactions, improving atom economy and reducing overall step count. Despite this, these reactions frequently run under reaction conditions that leave room for improved sustainability. Herein, we describe a recent advance in our ruthenium-catalysed C-H arylation methodology that aims to address some of the environmental impacts associated with this procedure, including solvent choice, reaction temperature, reaction time, and loading of the ruthenium catalyst. We believe that our findings demonstrate a reaction with improved environmental credentials and showcase it on a multi-gram scale within an industrial setting.

A Desaturative Approach for Aromatic Aldehyde Synthesis via Synergistic Enamine, Photoredox and Cobalt Triple Catalysis.

Aromatic aldehydes are fundamental intermediates that are widely utilised for the synthesis of important materials across the broad spectrum of chemical industries. Accessing highly substituted derivatives can often be difficult as their functionalizations are generally performed via electrophilic aromatic substitution, SE Ar. Here we provide an alternative and mechanistically distinct approach whereby aromatic aldehydes are assembled from saturated precursors via a desaturative process. This novel strategy harnesses the high-fidelity of Diels-Alder cycloadditions to quickly construct multi-substituted cyclohexenecarbaldehyde cores which undergo desaturation via the synergistic interplay of enamine, photoredox and cobalt triple catalysis.

Exploration of a Nitromethane-Carbonylation Strategy during Route Design of an Atropisomeric KRASG12C Inhibitor.

Route design and proof of concept synthesis was conducted on a synthetically challenging atropisomeric KRASG12C inhibitor to support clinical API manufacture. Improvements to the synthesis of a chiral piperazine fragment gave reduced step count and streamlined protecting group strategy via the formation and methanol ring opening of an N-carboxy-anhydride (NCA). The complex atropisomeric nitroquinoline was accessed via an early stage salt-resolution followed by a formal two-part nitromethane-carbonylation, avoiding a high temperature Gould-Jacobs cyclization that previously led to atropisomer racemization. The substrate scope of the formal nitromethane-carbonylation strategy was further explored for a range of ortho-substituted bromo/iodo unprotected anilines.

Photocatalysis in the Life Science Industry.

In the pursuit of new pharmaceuticals and agrochemicals, chemists in the life science industry require access to mild and robust synthetic methodologies to systematically modify chemical structures, explore novel chemical space, and enable efficient synthesis. In this context, photocatalysis has emerged as a powerful technology for the synthesis of complex and often highly functionalized molecules. This Review aims to summarize the published contributions to the field from the life science industry, including research from industrial-academic partnerships. An overview of the synthetic methodologies developed and strategic applications in chemical synthesis, including peptide functionalization, isotope labeling, and both DNA-encoded and traditional library synthesis, is provided, along with a summary of the state-of-the-art in photoreactor technology and the effective upscaling of photocatalytic reactions.

Radical hydroxymethylation of alkyl iodides using formaldehyde as a C1 synthon.

Radical hydroxymethylation using formaldehyde as a C1 synthon is challenging due to the reversible and endothermic nature of the addition process. Here we report a strategy that couples alkyl iodide building blocks with formaldehyde through the use of photocatalysis and a phosphine additive. Halogen-atom transfer (XAT) from α-aminoalkyl radicals is leveraged to convert the iodide into the corresponding open-shell species, while its following addition to formaldehyde is rendered irreversible by trapping the transient O-radical with PPh3. This event delivers a phosphoranyl radical that re-generates the alkyl radical and provides the hydroxymethylated product.

A photochemical dehydrogenative strategy for aniline synthesis.

Chemical reactions that reliably join two molecular fragments together (cross-couplings) are essential to the discovery and manufacture of pharmaceuticals and agrochemicals1,2. The introduction of amines onto functionalized aromatics at specific and pre-determined positions (ortho versus meta versus para) is currently achievable only in transition-metal-catalysed processes and requires halogen- or boron-containing substrates3-6. The introduction of these groups around the aromatic unit is dictated by the intrinsic reactivity profile of the method (electrophilic halogenation or C-H borylation) so selective targeting of all positions is often not possible. Here we report a non-canonical cross-coupling approach for the construction of anilines, exploiting saturated cyclohexanones as aryl electrophile surrogates. Condensation between amines and carbonyls, a process that frequently occurs in nature and is often used by (bio-)organic chemists7, enables a predetermined and site-selective carbon-nitrogen (C-N) bond formation, while a photoredox- and cobalt-based catalytic system progressively desaturates the cyclohexene ring en route to the aniline. Given that functionalized cyclohexanones are readily accessible with complete regiocontrol using the well established carbonyl reactivity, this approach bypasses some of the frequent selectivity issues of aromatic chemistry. We demonstrate the utility of this C-N coupling protocol by preparing commercial medicines and by the late-stage amination-aromatization of natural products, steroids and terpene feedstocks.

Practical and regioselective amination of arenes using alkyl amines.

The formation of carbon-nitrogen bonds for the preparation of aromatic amines is among the top five reactions carried out globally for the production of high-value materials, ranging from from bulk chemicals to pharmaceuticals and polymers. As a result of this ubiquity and diversity, methods for their preparation impact the full spectrum of chemical syntheses in academia and industry. In general, these molecules are assembled through the stepwise introduction of a reactivity handle in place of an aromatic C-H bond (that is, a nitro group, halogen or boronic acid) and a subsequent functionalization or cross-coupling. Here we show that aromatic amines can be constructed by direct reaction of arenes and alkyl amines using photocatalysis, without the need for pre-functionalization. The process enables the easy preparation of advanced building blocks, tolerates a broad range of functionalities, and multigram scale can be achieved via a batch-to-flow protocol. The merit of this strategy as a late-stage functionalization platform has been demonstrated by the modification of several drugs, agrochemicals, peptides, chiral catalysts, polymers and organometallic complexes.

Photoinduced decarboxylative azidation of cyclic amino acids.

The direct decarboxylative azidation of cyclic α-amino acids has been achieved via visible light-mediated organo-photoredox catalysis. This synthetic strategy allows the simple preparation of azide-contaning building blocks and has been used in the selective modification of N-terminal proline residues of two di-peptides.

Correction: A dual photoredox-nickel strategy for remote functionalization via iminyl radicals: radical ring-opening-arylation, -vinylation and -alkylation cascades.

[This corrects the article DOI: 10.1039/C9SC02616A.].

A dual photoredox-nickel strategy for remote functionalization via iminyl radicals: radical ring-opening-arylation, -vinylation and -alkylation cascades.

A divergent strategy for the remote arylation, vinylation and alkylation of nitriles is described. These processes proceed through the photoredox generation of a cyclic iminyl radical and its following ring-opening reaction. The distal nitrile radical is then engaged in nickel-based catalytic cycles to form C-C bonds with aryl bromides, alkynes and alkyl bromides.

Photoinduced Remote Functionalization of Amides and Amines Using Electrophilic Nitrogen Radicals.

The selective functionalization of C(sp3 )-H bonds at distal positions to functional groups is a challenging task in synthetic chemistry. Reported here is a photoinduced radical cascade strategy for the divergent functionalization of amides and protected amines. The process is based on the oxidative generation of electrophilic amidyl radicals and their subsequent transposition by 1,5-H-atom transfer, resulting in remote fluorination, chlorination and, for the first time, thioetherification, cyanation, and alkynylation. The process is tolerant of most common functional groups and delivers useful building blocks that can be further elaborated. The utility of this strategy is demonstrated through the late-stage functionalization of amino acids and a dipeptide.

Hydroxylamine Derivatives as Nitrogen-Radical Precursors in Visible-Light Photochemistry.

In recent years, hydroxylamines derivatives have been exploited as nitrogen-radical precursors in visible-light photochemistry. Their ability to serve as electrophores in redox chemistry has propelled the development of many novel transformations. Fundamental mechanistic aspects as well as the importance in the preparation of nitrogen-containing molecules will be highlighted.

Photoinduced Remote Functionalisations by Iminyl Radical Promoted C-C and C-H Bond Cleavage Cascades.

A photoinduced cascade strategy leading to a variety of differentially functionalised nitriles and ketones has been developed. These reactions rely on the oxidative generation of iminyl radicals from simple oximes. Radical transposition by C(sp3 )-(sp3 ) and C(sp3 )-H bond cleavage gives access to distal carbon radicals that undergo SH 2 functionalisations. These mild, visible-light-mediated procedures can be used for remote fluorination, chlorination, and azidation, and were applied to the modification of bioactive and structurally complex molecules.

Visible-light-mediated generation of nitrile oxides for the photoredox synthesis of isoxazolines and isoxazoles.

Visible-light photoredox catalysis enables the synthesis of biologically relevant isoxazolines and isoxazoles from hydroxyimino acids. The process shows broad functional group compatibility and mechanistic and computational studies support a visible-light-mediated generation of nitrile oxides by two sequential oxidative single electron transfer processes.

Elevated Plasma Angiopoietin-2 Levels Are Associated With Fluid Overload, Organ Dysfunction, and Mortality in Human Septic Shock.

OBJECTIVES: Angiopoietins modulate endothelial permeability via endothelial cell junctions. Angiopoietin-2 blocks the angiopoietin-1/Tie-2 interaction that stabilizes these junctions, and elevated plasma angiopoietin-2 levels are associated with vascular leakage. We hypothesized that plasma angiopoietin-1 and angiopoietin-2 levels are associated with indirect markers of increased vascular permeability, organ dysfunction, mortality, and plasma proinflammatory cytokine levels in human septic shock. DESIGN: Multicenter observational cohort study derived from a randomized controlled trial (Vasopressin and Septic Shock Trial of vasopressin versus norepinephrine in septic shock). SETTING: ICUs of hospitals in Canada, Australia, and the United States. PATIENTS: Three hundred forty-one patients in the randomized, controlled Vasopressin and Septic Shock Trial trial of vasopressin versus norepinephrine in septic shock. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: We measured plasma levels of angiopoietin-1 and angiopoietin-2 at study baseline and determined their association with percent fluid overload and acute organ dysfunction and generated a receiver operating characteristic curve for plasma angiopoietin-2 levels versus acute kidney injury. We also determined the association of angiopoietin-1 and angiopoietin-2 levels with hemodynamics, mortality, and plasma cytokine levels. Plasma angiopoietin-2 levels were directly associated with percent fluid overload at baseline (rs = 0.18; p = 0.0008) and at 6 hours (rs = 0.13; p = 0.023), but not at 24 hours (rs = 0.041; p = 0.46). Plasma angiopoietin-2 levels were associated with the development of hepatic (p < 0.0001) and coagulation (p < 0.0001) dysfunction and acute kidney injury (p < 0.0001). Receiver operating characteristic curve had an area under the curve of 0.73 for acute kidney injury. angiopoietin-2 levels were also inversely associated with days alive (r = -0.24; p = 0.010) and positively associated with increased 7-day (log-rank trend chi-square = 5.9; p = 0.015) and 28-day (log-rank chi square = 4.9; p = 0.027) mortality. A threshold of angiopoietin-2 levels above the first quartile (> 5,807 pg/mL) was observed to be associated with increased mortality risk, which aligns with prior studies. Plasma angiopoietin-2 levels were positively associated with plasma cytokine levels, including tumor necrosis factor-α and interleukin-6 at baseline (rs = 0.39; p < 0.0001 and rs = 0.51; p < 0.0001) and at 24 hours (rs = 0.29; p < 0.0001 and rs = 0.41; p < 0.0001). CONCLUSIONS: Increased plasma angiopoietin-2 levels are associated with increased fluid overload, hepatic and coagulation dysfunction, acute kidney injury, mortality, and plasma cytokines in human septic shock. angiopoietin-2 activation may increase vascular leakage leading to increased fluid requirements, organ dysfunction, and death from septic shock.

Photochemical Perfluoroalkylation with Pyridine N-Oxides: Mechanistic Insights and Performance on a Kilogram Scale.

The direct trifluoromethylation of (hetero)arenes is a process of high importance to the pharmaceutical industry. Many reagents exist for this purpose and have found widespread use in discovery efforts; however, the step-intensive preparation of these reagents and their corresponding cost have resulted in minimal use of these methods in large-scale applications. For the ready transition of direct trifluoromethylation methodologies to large-scale application, the further development of processes utilizing inexpensive CF3 sources available on a metric ton scale is highly desirable. We report the use of pyridine N-oxide derivatives in concert with trifluoroacetic anhydride to promote a high-yielding and scalable trifluoromethylation reaction. Key mechanistic insights include the observation of electron donor-acceptor complexes in solution as well as a high dependence on photon flux. These observations have culminated in the application of this chemistry on a kilogram scale, demonstrating the utility of this reagent combination for preparative applications.

The role of genomics to identify biomarkers and signaling molecules during severe sepsis.

Early strategies to diagnose, manage and predict outcome of sepsis are essential to further improve morbidity and mortality of sepsis. Whereas biomarkers have become mainstay in other fields of medicine, their clinical utility in sepsis remains generally much less proven and so biomarkers are much less used clinically. The Human Genome Project embellished genomics, transcriptomics, proteomics and metabolomics and continues to expand our knowledge of the genetic, gene expression, protein translational and metabolic discoveries that could lead to clinical biomarker tests related to sepsis thereby allowing insight into the disease as never seen before. We explore the genomic approach to biomarker identification and validation by reviewing pertinent studies related to the diagnosis (diagnostic biomarkers), prediction of response to therapies (predictive biomarkers) and (prognostic biomarkers) outcomes of sepsis.

A Visible-Light-Mediated Radical Smiles Rearrangement and its Application to the Synthesis of a Difluoro-Substituted Spirocyclic ORL-1 Antagonist.

A visible-light-mediated radical Smiles rearrangement has been developed to address the challenging synthesis of the gem-difluoro group present in an opioid receptor-like 1 (ORL-1) antagonist that is currently in development for the treatment of depression and/or obesity. This method enables the direct and efficient introduction of the difluoroethanol motif into a range of aryl and heteroaryl systems, representing a new disconnection for the synthesis of this versatile moiety. When applied to the target compound, the photochemical step could be conducted on 15 g scale using industrially relevant [Ru(bpy)3Cl2] catalyst loadings of 0.01 mol %. This transformation is part of an overall five-step route to the antagonist that compares favorably to the current synthetic sequence and demonstrates, in this specific case, a clear strategic benefit of photocatalysis.