Ferrocene-derived P,N ligands : synthesis and application in enantioselective catalysis

Due to their unique steric and electronic properties, air-stability and modular structure, chiral hybrid P,N-ferrocenyl ligands play a prominent role in the field of asymmetric catalysis. This report aims to give a concise introduction to the syntheses of chiral hybrid P,N-ferrocenyl ligands and presents an overview of their application in enantioselective catalysis. This review is of special interest to chemists working on ligand design and asymmetric catalysis, as well as to the broader organic and inorganic community

Synthesis and application of chiral dienes and chiral imidates as ligands for transition metal catalysis

In this dissertation, two main ligandclasses have been studied: chiral diene ligands and chiral imidate ligands. We developed a novel route to synthesize chiral disubstituted bicyclo[2.2.1]heptadienes (R= i-Bu, c-Hex, Benzyl and allyl) starting from enantiomerically pure bistriflate. The synthesized diene ligands were tested in the rhodium(I)-catalyzed 1,4-addition of phenylboronic acids to cyclic enones (up to 96% ee) and α-acetamido acrylic ester and in the rhodium(I)-catalyzed 1,2-addition of phenylboronic acids to benzaldehydes (up to 48% ee). We introduced chiral imidates as a novel nitrogen-based ligand family. These imidates, with an exocyclic nitrogen, have never before been reported in literature. We showed that these imidate ligands could be obtained readily via a one-step synthesis starting from a central precursor in excellent yields. Moreover, imidate ligands could further be fine-tuned when substituents were put on the aromatic ring of the imidate ligand precursor. The synthesized monodentate and bidentate ligands were tested in several asymmetric test reactions. In the copper(I)-catalyzed asymmetric aziridinations, we obtained usually high yields (up to 90% yield) and moderate enantioselectivity (51% ee) with a bidentate imidate ligand. The asymmetric addition of diethylzinc to benzaldehyde resulted in high yields (up to 87% yield) and good enantioselectivities (up to 76% ee). However, the best result was obtained in the asymmetric allylic alkylation with an imidate with a binaphtylbackbone: a moderate yield (53% yield) with an excellent selectivity (95% ee). Futhermore, we developed successfully hybrid imidate-phosphane ligands as a new type of P,N ligands. These ligands are easily accessible in one step via a condensation of a commercially available aminophosphane and an imidate ligand precursor. The ligands were demonstrated to be highly valuable in palladium-catalyzed allylic substitution reactions. Excellent performance of this catalyst system was observed in the allylic alkylation of 1,3-diphenyl-2-propenyl acetate with various nucleophiles (up to 99% yield and >99% ee). Moreover, the allylic alkylation of linear unhindered and cyclic substrates resulted in good conversions and enantioselectivities. The cyclic imidate ligand precursor could also be used efficiently as a synthetic intermediate for the synthesis of chiral oxazoline alcohol ligands and the synthesis of chiral imidazolidines

Membrane-based TBADT recovery as a strategy to increase the sustainability of continuous-flow photocatalytic HAT transformations

Photocatalytic hydrogen atom transfer (HAT) processes have been the object of numerous studies showcasing the potential of the homogeneous photocatalyst tetrabutylammonium decatungstate (TBADT) for the functionalization of C(sp(3))–H bonds. However, to translate these studies into large-scale industrial processes, careful considerations of catalyst loading, cost, and removal are required. This work presents organic solvent nanofiltration (OSN) as an answer to reduce TBADT consumption, increase its turnover number and lower its concentration in the product solution, thus enabling large-scale photocatalytic HAT-based transformations. The operating parameters for a suitable membrane for TBADT recovery in acetonitrile were optimized. Continuous photocatalytic C(sp(3))-H alkylation and amination reactions were carried out with in-line TBADT recovery via two OSN steps. Promisingly, the observed product yields for the reactions with in-line catalyst recycling are comparable to those of reactions performed with pristine TBADT, therefore highlighting that not only catalyst recovery (>99%, TON > 8400) is a possibility, but also that it does not happen at the expense of reaction performance

From Crossroads to Godzilla: the cinematic legacies of the first postwar nuclear tests

No abstract available

Oppenheimer the actor: the curious 1946 film Atomic Power featuring the scientist as himself

No abstract available

Examining the Gap: Compensation Disparities between Male and Female Physician Assistants.

BACKGROUND: Compensation disparities between men and women have been problematic for decades, and there is considerable evidence that the gap cannot be entirely explained by nongender factors. The current study examined the compensation gap in the physician assistant (PA) profession. METHODS: Compensation data from 2014 was collected by the American Academy of PAs in 2015. Practice variables, including experience, specialty, and hours worked, were controlled for in an ordinary least-squares sequential regression model to examine whether there remained a disparity in total compensation. In addition, the absolute disparity in compensation was compared with historical data collected by American Academy of PAs over the previous 1.5 decades. RESULTS: Without controlling for practice variables, a total compensation disparity of $16,052 existed between men and women in the PA profession. Even after PA practice variables were controlled for, a total compensation disparity of$9,695 remained between men and women (95% confidence interval, $8,438-$10,952). A 17-year trend indicates the absolute disparity between men and women has not lessened, although the disparity as a percent of male compensation has decreased in recent years. CONCLUSIONS: There remain challenges to ensuring pay equality in the PA profession. Even when compensation-relevant factors such as experience, hours worked, specialty, postgraduate training, region, and call are controlled for, there is still a substantial gender disparity in PA compensation. Remedies that may address this pay inequality include raising awareness of compensation disparities, teaching effective negotiation skills, assisting employers as they develop equitable compensation plans, having less reliance on past salary in position negotiation, and professional associations advocating for policies that support equal wages and opportunities, regardless of personal characteristics

Technological Innovations in Photochemistry for Organic Synthesis: Flow Chemistry, High-Throughput Experimentation, Scale-up, and Photoelectrochemistry

[Image: see text] Photoinduced chemical transformations have received in recent years a tremendous amount of attention, providing a plethora of opportunities to synthetic organic chemists. However, performing a photochemical transformation can be quite a challenge because of various issues related to the delivery of photons. These challenges have barred the widespread adoption of photochemical steps in the chemical industry. However, in the past decade, several technological innovations have led to more reproducible, selective, and scalable photoinduced reactions. Herein, we provide a comprehensive overview of these exciting technological advances, including flow chemistry, high-throughput experimentation, reactor design and scale-up, and the combination of photo- and electro-chemistry

Visible-light-mediated selective arylation of cysteine in batch and flow

A mild visible-light-mediated strategy for cysteine arylation is presented. The method relies on the use of eosin Y as a metal-free photocatalyst and aryldiazonium salts as arylating agents. The reaction can be significantly accelerated in a microflow reactor, whilst allowing the insitu formation of the required diazonium salts. The batch and flow protocol described herein can be applied to obtain a broad series of arylated cysteine derivatives and arylated cysteine-containing dipeptides. Moreover, the method was applied to the chemoselective arylation of a model peptide in biocompatible reaction conditions (room temperature, phosphate-buffered saline (PBS) buffer) within a short reaction time

The implications of K-Ar glauconite dating of the Diest Formation on the paleogeography of the Upper Miocene in Belgium

The glauconite-rich Diest Formation in central and north Belgium contains sands in the Campine subsurface and the hilly Hageland area that can be distinguished from each other. The Hageland Diest Sands member contains no stratigraphically relevant fossils while in the Campine subsurface dinoflagellate cysts are common and show a stratigraphic range covering the entire Tortonian stage. K-Ar dates were determined for glauconite from 13 selected samples spread over both areas. A glauconite date corresponding to the earliest Tortonian indicates newly formed glauconite was incorporated into a greensand at the base of the Diest Formation in the central Campine area. All other dates point at reworked glauconite and can be organized in two groups, one reflecting a Burdigalian age and another reflecting a Langhian age. These data and the thickness and glauconite content of the Diest Formation imply massive reworking of older Miocene deposits. The paleogeographic implications of these data lead to the tentative recognition of two Tortonian sedimentary sequences. An older one corresponding to dinoflagellate biochron DN8 comprises the Deurne Member, part of the Dessel Member, the Hageland Diest member, the eastern Campine Diest member and some basal sands of the Diest Formation in the central Campine. A younger sequence corresponding to dinoilagellate biochrons DN9 and 10 was strongly influenced by the prograding proto-Rhine delta front in the Roer Valley Graben to the northeast. The subsiding Campine basin was filled from east to west during this second cycle