An Umpolung Approach to Acyclic 1,4-Dicarbonyl Amides via Photoredox-Generated Carbamoyl Radicals.

A method for the generation and reaction of carbamoyl radicals from oxamate salts, followed by reaction with electron-poor olefins, is described. The oxamate salt acts as a reductive quencher in the photoredox catalytic cycle, allowing mild and mass-efficient formation of 1,4-dicarbonyl products; a challenging transformation in the context of functionalized amide formation. Increased understanding has been obtained by the use of ab initio calculations, in support of experimental observations. Furthermore, steps have been taken towards an environmentally-friendly protocol, by utilizing sodium as a cheap and low mass counterion, and demonstrating successful reactions using a metal-free photocatalyst and a sustainable, non-toxic solvent system.

Managing emerging mutagenicity risks: Late stage mutagenic impurity control within the atovaquone second generation synthesis.

The mutagenic-impurity control strategy for a second generation manufacturing route to the non-mutagenic antipneumocystic agent atovaquone (2-((1R,4R)-4-(4-chlorophenyl)cyclohexyl)-3-hydroxynaphthalene-1,4-dione) 1 is described. Preliminary assessment highlighted multiple materials of concern which were largely discharged either through returning a negative bacterial mutagenicity assay or through confidence that the impurity would be purged during the downstream processing from when it was first introduced. Additional genotoxicity testing highlighted two materials of concern where initial assessment suggested that testing for these impurities at trace levels within the drug substance would be required. Following a thorough review of process purging detail, spiking and purging experimentation, and an understanding of the process parameters to which they were exposed an ICH M7 Option 4 approach could be justified for their control. The development of two 1H NMR spectroscopy methods for measurement of these impurities is also described as well as a proposed summary table for describing the underlying rationale for ICH M7 control rationales to regulators. This manuscript demonstrates that process purging of potential mutagenic impurities can be realised even when they are introduced in the later stages of a process and highlights the importance of scientific understanding rather than relying on a stage-counting approach.

A Practical and General Amidation Method from Isocyanates Enabled by Flow Technology.

The addition of carbon nucleophiles to isocyanates represents a conceptually flexible and efficient approach to the preparation of amides. This general synthetic strategy has, however, been relatively underutilized owing to narrow substrate tolerance and the requirement for less favourable reaction conditions. Herein, we disclose a high-yielding, mass-efficient, and scalable method with appreciable functional group tolerance for the formation of amides by reaction of Grignard reagents with isocyanates. Through the application of flow chemistry and the use of substoichiometric amounts of CuBr2 , this process has been developed to encompass a broad range of substrates, including reactants found to be incompatible with previously published procedures.

Discovery of GSK143, a highly potent, selective and orally efficacious spleen tyrosine kinase inhibitor.

The lead optimisation of the diaminopyrimidine carboxamide series of spleen tyrosine kinase inhibitors is described. The medicinal chemistry strategy was focused on optimising the human whole blood activity whilst achieving a sufficient margin over liability kinases and hERG activity. GSK143 is a potent and highly selective SYK inhibitor showing good efficacy in the rat Arthus model.

Synthesis of small molecules with high scaffold diversity: exploitation of metathesis cascades in combination with inter- and intramolecular Diels-Alder reactions.

Our knowledge of the biological relevance of regions of chemical space is shaped, in large part, by the synthetic accessibility of small molecules. Historically, however, chemists have explored chemical space in an exceptionally uneven and unsystematic way. We have previously demonstrated that metathesis cascade chemistry may be harnessed to yield small molecule collections with high scaffold diversity. Here, we describe the extent to which inter- and intramolecular Diels-Alder reactions, when used in conjunction with metathesis cascades, can extend the range of molecular scaffolds that are accessible. A range of metathesis substrates was prepared from combinations of two or three building blocks. Metathesis cascades were exploited to "reprogram" the molecular scaffolds. In many cases, the metathesis products were 1,3-dienes, which were potential substrates for either inter- or intramolecular Diels-Alder reactions. The synthesis and functionalisation of the products was often facilitated by fluorous tagging, for example by using a "safety-catch" linker that we have developed. It was demonstrated that, in certain cases, Diels-Alder reactions could extend the range of molecular scaffolds that may be prepared by using metathesis cascade reactions.

Et3SiH + KO t Bu provide multiple reactive intermediates that compete in the reactions and rearrangements of benzylnitriles and indolenines.

The combination of potassium tert-butoxide and triethylsilane is unusual because it generates multiple different types of reactive intermediates simultaneously that provide access to (i) silyl radical reactions, (ii) hydrogen atom transfer reactions to closed shell molecules and to radicals, (iii) electron transfer reductions and (iv) hydride ion chemistry, giving scope for unprecedented outcomes. Until now, reactions with this reagent pair have generally been explained by reference to one of the intermediates, but we now highlight the interplay and competition between them.

New reductive rearrangement of N-arylindoles triggered by the Grubbs-Stoltz reagent Et3SiH/KO t Bu.

N-Arylindoles are transformed into dihydroacridines in a new type of rearrangement, through heating with triethylsilane and potassium tert-butoxide. Studies indicate that the pathway involves (i) the formation of indole radical anions followed by fragmentation of the indole C2-N bond, and (ii) a ring-closing reaction that follows a potassium-ion dependent hydrogen atom transfer step. Unexpected behaviors of 'radical-trap' substrates prove very helpful in framing the proposed mechanism.

N-Heterocyclic Carbene-Mediated Microfluidic Oxidative Electrosynthesis of Amides from Aldehydes.

A flow process for N-Heterocyclic Carbene (NHC)-mediated anodic oxidative amidation of aldehydes is described, employing an undivided microfluidic electrolysis cell to oxidize Breslow intermediates. After electrochemical oxidation, the reaction of the intermediate N-acylated thiazolium cation with primary amines is completed by passage through a heating cell to achieve high conversion in a single pass. The flow mixing regimen circumvented the issue of competing imine formation between the aldehyde and amine substrates, which otherwise prevented formation of the desired product. High yields (71-99%), productivities (up to 2.6 g h(-1)), and current efficiencies (65-91%) were realized for 19 amides.

N-Heterocyclic Carbene-Mediated Oxidative Electrosynthesis of Esters in a Microflow Cell.

An efficient N-heterocyclic carbene (NHC)-mediated oxidative esterification of aldehydes has been achieved in an undivided microfluidic electrolysis cell at ambient temperature. Productivities of up to 4.3 g h(-1) in a single pass are demonstrated, with excellent yields and conversions for 19 examples presented. Notably, the oxidative acylation reactions were shown to proceed with a 1:1 stoichiometry of aldehyde and alcohol (for primary alcohols), with remarkably short residence times in the electrolysis cell (<13 s), and without added electrolyte.

Developing a general ward nursing dashboard.

The seventh and final article in the series on Leading Better Care explores some of the challenges in clinical practice relating to the use of data and making information meaningful to senior charge nurses and ward sisters. It describes the collaborative approach taken by NHS Lanarkshire, which involved nursing staff, programme leads and the eHealth team in the development of a general ward nursing dashboard as a means of ensuring safe, effective person-centred care. The article also illustrates how this web-based data-reporting programme is used to support clinical practice.

TEMPO-mediated electrooxidation of primary and secondary alcohols in a microfluidic electrolytic cell.

A general procedure for the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated electrooxidation of primary and secondary alcohols modified for application in a microfluidic electrolytic cell is described. The electrocatalytic system utilises a buffered aqueous tert-butanol reaction medium, which operates effectively without the requirement for additional electrolyte, providing a mild protocol for the oxidation of alcohols to aldehydes and ketones at ambient temperature on a laboratory scale. Optimisation of the process is discussed along with the oxidation of 15 representative alcohols.

A fluorous-tagged linker from which small molecules are released by ring-closing metathesis.

A fluorous-tagged linker for the parallel synthesis of small- and medium-ring and macrocyclic nitrogen heterocycles using ring-closing metathesis is described. The linker was designed such that "cyclization-release" of the cyclic heterocyclic products was coupled with liberation of the active catalyst. The design of the linker was validated using a non-fluorous-tagged model. A wide range of unsaturated alcohols were used as reagents to functionalize a fluorous-tagged sulfonamide, (Z)-{N-[4-(2-(N'-3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)-4-methylsulfonamido)methylallyloxy]but-2-enyl}-2-nitrobenzenesulfonamide, using Fukuyama-Mitsunobu reactions; in each case, fluorous-solid-phase extraction (F-SPE) was used to purify the functionalized linker from the excess reagents. In general, the "cyclization-release" of cyclic products was triggered using a light-fluorous tagged derivative of the Grubbs-Hoveyda second-generation catalyst. After the metathesis step, F-SPE was used to purify released cyclic compounds from the fluorous-tagged linker and the fluorous-tagged catalyst. The scope and limitations of the approach were determined using a range of substrates which probed different aspects of the functionalization and metathesis steps. In the study as a whole, a wide range of small- and medium-ring and macrocyclic nitrogen heterocycles were prepared using polyene and polyenyne metathesis cascades.

An efficient method for synthesising unsymmetrical silaketals: substrates for ring-closing, including macrocycle-closing, metathesis.

Diisopropylsilyl ethers were activated with N-bromosuccinimide, and reacted with a fluorous-tagged alcohol, to yield tethered substrates for ring-closing metathesis reactions.