Heart of gold: enabling ligands for oxidative addition of haloorganics in Au(I)/Au(III) catalysed cross-coupling reactions

The field of Au-catalysis has been an area rich with new discoveries due to the unique properties of the lustrous element. In the past decade, developments in Au(I)/Au(III) cross-coupling methodology have been made possible with the use of external oxidants that facilitate the challenging oxidation of Au(I) to Au(III) in a stable and catalytically competent fashion. Until recently, Au-chemistry was not known to undergo catalytic transformations that feature oxidative addition of haloarenes like those that were made famous by transition metals such as Pd and Ni. The discovery that ligand modification could facilitate the oxidative addition of Au(I) with haloorganics to provide Au(III) intermediates that are competent in other areas of catalysis (i.e. Lewis acid catalysis) has revolutionized this field and has led to the invention of new cross-coupling methodology. The recent advances at the leading edge in the emerging field of Au(I)/Au(III) catalysis under redox-neutral conditions are highlighted.

Harnessing Radical Chemistry via Electrochemical Transition Metal Catalysis

The merger of transition metal catalysis and electroorganic synthesis has recently emerged as a versatile platform for the development of highly enabling radical reactions in a sustainable fashion. Electrochemistry provides access to highly reactive radical species under extremely mild reaction conditions from abundant native functionalities. Transition metal catalysts can be used as redox-active electrocatalysts to shuttle electrons, chiral information to organic substrates, and the reactive intermediates in the electrolytic systems. The combination of these strategies in this mechanistic paradigm thus makes the generation and utilization of radical species in a chemoselective manner and allows further application to more synthetically attractive enantioselective radical transformations. This perspective discusses key advances over the past few years in the field of electrochemical transition metal catalysis and demonstrates how the unique features of this strategy permit challenging or previously elusive transformations via radical pathways to be successfully achieved.

Recent Advances in Titanium Radical Redox Catalysis

New catalytic strategies that leverage single-electron redox events have provided chemists with useful tools for solving synthetic problems. In this context, Ti offers opportunities that are complementary to late transition metals for reaction discovery. Following foundational work on epoxide reductive functionalization, recent methodological advances have significantly expanded the repertoire of Ti radical chemistry. This Synopsis summarizes recent developments in the burgeoning area of Ti radical catalysis with a focus on innovative catalytic strategies such as radical redox-relay and dual catalysis.

Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols

Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely, bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton transfer/electron transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.

Hydrogen Atom Transfer Reactions via Photoredox Catalyzed Chlorine Atom Generation

The selective functionalization of chemically inert C-H bonds remains to be fully realized in achieving organic transformations that are redox-neutral, waste-limiting, and atom-economical. The catalytic generation of chlorine atoms from chloride ions is one of the most challenging redox processes, where the requirement of harsh and oxidizing reaction conditions renders it seldom utilized in synthetic applications. We report the mild, controlled, and catalytic generation of chlorine atoms as a new opportunity for access to a wide variety of hydrogen atom transfer (HAT) reactions owing to the high stability of HCl. The discovery of the photoredox mediated generation of chlorine atoms with Ir-based polypyridyl complex, [Ir(dF(CF₃ )ppy)₂ (dtbbpy)]Cl, under blue LED irradiation is reported.

Transformations of Isonitriles with Bromoalkanes Using Photoredox Gold Catalysis

Isonitriles have excellent electronic compatibility to react with free radicals. Recently, photoredox catalysis has emerged as a powerful tool for the construction of C-C bonds with few protocols for alkylative heterocycle synthesis through isonitrile addition. Herein, we describe the photocatalytic generation of alkyl radicals from unactivated bromoalkanes as part of an efficient cross-coupling strategy for the diversification of isonitriles using a dimeric gold(I) photoredox catalyst, [Au₂(dppm)₂]Cl₂.

Recent advances in mono and binuclear gold photoredox catalysis

In this minireview, recent developments in the field of photoredox catalysis and the applications of mono and binuclear Au(i) complexes in organic transformations are discussed.

The photochemical alkylation and reduction of heteroarenes

The functionalization of heteroarenes has been integral to the structural diversification of medicinally active molecules such as quinolines, pyridines, and phenanthridines. Electron-deficient heteroarenes are electronically compatible to react with relatively nucleophilic free radicals such as hydroxyalkyl. However, the radical functionalization of such heteroarenes has been marked by the use of transition-metal catalyzed processes that require initiators and stoichiometric oxidants. Herein, we describe the photochemical alkylation of quinolines, pyridines and phenanthridines, where through direct excitation of the protonated heterocycle, alcohols and ethers, such as methanol and THF, can serve as alkylating agents. We also report the discovery of a photochemical reduction of these heteroarenes using only iPrOH and HCl. Mechanistic studies to elucidate the underlying mechanism of these transformations, and preliminary results on catalytic methylations are also reported.

Photoredox meets gold Lewis acid catalysis in the alkylative semipinacol rearrangement: a photocatalyst with a dark side

The alkylative semipinacol rearrangement of a variety of TMS protected α-styrenyl substituted cyclic alcohols with unactivated bromoalkanes that merge photoredox and Au(i)/Au(iii) catalysis has been achieved.

Direct alkylation of heteroarenes with unactivated bromoalkanes using photoredox gold catalysis

Although visible light photoredox catalysis has emerged as a powerful tool for the construction of C-C bonds, common catalysts and/or their photoexcited states suffer from low redox potentials, limiting their applicability to alkyl radical generation from substrates with activated carbon-halogen bonds. Radicals derived from these activated compounds, being highly electrophilic or stabilized, do not undergo efficient addition to heteroarenes. Herein we describe the photocatalytic generation of nucleophilic alkyl radicals from unactivated bromoalkanes as part of a universal and efficient cross-coupling strategy for the direct alkylation of heteroarenes using a dimeric gold(i) photoredox catalyst, [Au2(bis(diphenylphosphino)methane)2]Cl2. The method proves to be efficient for alkylation of arenes under mild conditions in the absence of directing groups.

Polynuclear gold(i) complexes in photoredox catalysis: understanding their reactivity through characterization and kinetic analysis

The light mediated reduction of unactivated carbon–halogen bonds using polynuclear gold(i) complexes provides a mild and temporally controlled route to the generation of C–H, and C–C bonds.

Unilateral renal agenesis associated with congenital bilateral absence of the vas deferens: phenotypic findings and genetic considerations

An association between congenital bilateral absence of the vas deferens (CBAVD), normal renal anatomy and cystic fibrosis (CF) gene mutations is well established (CF/CBAVD). We postulate that unilateral renal agenesis (URA) and CBAVD (URA/CBAVD) may have a non-CF mutation-mediated genetic basis that leads to abnormal development of the entire mesonephric duct at a very early stage in embryo development (< or =7 weeks). The physical, laboratory and radiographic findings of men with URA/CBAVD (n = 17) and CF/CBAVD (n = 97) were compared; the fertilization and pregnancy rates in the URA/CBAVD population calculated, and the incidence of renal agenesis in immediate family members and offspring of men with URA/CBAVD analysed. No statistical differences could be identified within any of the above comparisons. The fertilization rate for the URA/CBAVD group was 58.2 +/- 26.3%. Eight infants and two fetuses had normal renal anatomy, while one terminated male fetus had bilateral renal and vasal agenesis. Thirty first-order relatives had normal renal units. Anatomical expression of the reproductive ductal derivatives in men with URA/CBAVD and CF/CBAVD was similar, but the phenotypic outcome of the renal portion of the mesonephric duct was different. The potential for transmission of this fatal anomaly reinforces the need for prenatal ultrasounds with all pregnancies involving URA/CBAVD men.

Introducing annamarie jagose

SUMMARY Annamarie Jagose's fiction can be loosely divided into the early short stories and the later novels. The stories are generally feminist and lesbian in content and characters, and contain many traditional story elements. The novels, In Translation and Lulu,are more complex works. In these texts, Jagose is interested in "queering" identity, both heterosexual and homosexual, and in questioning the effectiveness of these traditional taxonomies. Both the stories and novels feature an exquisite control of language, a wry humour, and a deft understanding of human relationships.

Furazolidone-induced injury in the isolated perfused chicken heart

The Langendorff isolated heart preparation was adapted to determine the effect of furazolidone (0.5 and 2 micrograms/ml of perfusate) on hearts of 3-week-old broiler chickens. Following 115 minutes of perfusion, both concentrations of furazolidone caused approximately a two-fold increase in myocardial vascular resistance and a six-fold increase in lactate dehydrogenase release into the effluent fluid, compared with a control perfused group of isolated hearts (P less than 0.01). Ultrastructural alteration differences were not found between the drug-treated and control groups. It was concluded that: (i) furazolidone, at concentrations only moderately above therapeutic plasma concentrations, caused detrimental changes in myocardial vascular resistance and lactate dehydrogenase release and (ii) the isolated chicken heart preparation is an example of a cost-effective, reliable laboratory tool for screening potential cardiotoxins.