Catalytic constructive deoxygenation of lignin-derived phenols: new C-C bond formation processes from imidazole-sulfonates and ether cleavage reactions

Funding: UK Engineering and Physical Sciences Research Council (EPSRC)As part of a programme aimed at exploiting lignin as a chemical feedstock for less oxygenated fine chemicals, several catalytic C-C bond forming reactions utilising guaiacol imidazole sulfonate are demonstrated. These include the cross-coupling of a Grignard, a non-toxic cyanide source, a benzoxazole, and nitromethane. A modified Meyers reaction is used to accomplish a second constructive deoxygenation on a benzoxazole functionalised anisole.Publisher PDFPeer reviewe

Rhodium/phospholane-phosphite catalysts give unusually high regioselectivity in the enantioselective hydroformylation of vinyl arenes

Using the phospholane-phosphite ligand, BOBPHOS, almost perfect regioselectivities and high enantioselectivities (up to 92% ee) are observed in Rh catalysed enantioselective hydroformylation of vinyl arenes. This can be achieved under solvent-free conditions.PostprintPeer reviewe

Towards practical earth abundant reduction catalysis : design of improved catalysts for manganese catalysed hydrogenation

The authors thank EPSRC (grant code: 1654521) for DTG funding for MBW.Manganese catalysts derived from tridentate P,N,N ligands can be activated easily using weak bases for both ketone and ester hydrogenations. Kinetic studies indicate the ketone hydrogenations are 0th order in acetophenone, positive order in hydrogen and 1st order in catalyst. This implies that the rate determining step of the reaction was the activation of hydrogen. New ligand systems with varying donor strength were studied and it was possible to make the hydrogen activation significantly more efficient; a catalyst displaying around a 3-fold increase in initial Turn-Over Frequencies for the hydrogenation of acetophenone relative to the parent system was discovered as a result of these kinetic investigations. Ester hydrogenations and ketone transfer hydrogenation (isopropanol as reductant) are first order for both the substrate and catalysts. Kinetic studies also gained insight into catalyst stability and identified a working range in which the catalysts is stable throughout the catalytic reaction (and a larger working range where high yields can still be achieved). The new more active catalyst, combining an electron-rich phosphine with an electron-rich pyridine is capable of hydrogenating acetophenone using as little as 0.01 mol% catalyst at 65 oC. In all, protocols for reduction of 21 ketones and 15 esters are described.PostprintPeer reviewe

Remarkable co-catalyst effects on the enantioselective hydrogenation of unfunctionalised enamines : both enantiomers of product from the same enantiomer of catalyst

During studies on the enantioselective hydrogenation of unfunctionalised enamines, a very surprising switch in enantiopreference was observed; [((R,R)-Et-DUPHOS)-Rh(COD)]BF4 hydrogenates an enamine to give (R)-amine with up to 73% ee, but when iodine is added as a co-catalyst, the (S)-amine is formed with up to 61% ee. Mechanistic studies implicate a protonation-iminium ion reduction pathway.PostprintPeer reviewe

A consecutive process for C–C and C–N bond formation with high enantio-and diastereocontrol : direct reductive amination of chiral ketones using hydrogenation catalysts

Authors thank the University of St Andrews, and the EPSRC Centre for Doctoral Training in Critical Resource Catalysis (CRITICAT) for financial support [PhD studentship to SG; Grant code: EP/L016419/1].High diastereoselectivity was observed in the Rh-catalysed reductive amination of 3-arylcyclohexanones to form tertiary amines. This was incorporated into a one-pot enantioselective conjugate addition and diastereoselective reductive amination, including an example of assisted tandem catalysis.PostprintPeer reviewe

Towards the Industrial Implementation of Mn-based Catalyst for the Hydrogenation of Ketones and Carboxylic Esters

There is a constant pressure in industry to move away from platinum group metals (PGM) and achieve more environmentally friendly and sustainable production processes in the future. Recently developed Mn-based catalysts offer an interesting opportunity to complement established catalysts based on Ru. In this article, recent achievements in the field are highlighted and recent achievements in the collaboration of Solvias AG with the group of Prof. M. Clarke towards the implementation of these catalysts on industrial scale are outlined

The patient burden of screening mammography recall.

OBJECTIVE: The aim of this article is to evaluate the burden of direct and indirect costs borne by recalled patients after a false positive screening mammogram. METHODS: Women aged 40-75 years undergoing screening mammography were identified from a U.S. commercial claims database. Women were required to have 12 months pre- and 6 months post-index enrollment to identify utilization and exclude patients with subsequent cancer diagnoses. Recall was defined as the use of diagnostic mammography or breast ultrasound during 6 months post-index. Descriptive statistics were presented for recalled and non-recalled patients; differences were compared using the chi square test. Out-of-pocket costs were totaled by utilization type and in aggregate for all recall utilization. RESULTS: Of 1,723,139 patients with a mammography screening that were not diagnosed with breast cancer, 259,028 (15.0%) were recalled. Significant demographic differences were observed between recalled and non-recalled patients. The strongest drivers of patient costs were image-guided biopsy (mean $351 among 11.8$50; 80.1%), and ultrasound ($58; 65.7%), which accounted for 29.9%, 29.0%, and 27.5% of total recall costs, respectively. For many patients the entire cost of recall utilization was covered by the health plan. Total costs were substantially greater among patients with biopsy; one-third of all patients experienced multiple days of recall utilization. CONCLUSION: After a false positive screening mammography, recalled women incurred both direct medical costs and indirect time costs. The cost burden for women with employer-based insurance was dependent upon the type of utilization and extent of health plan coverage. Additional research and technologies are needed to address the entirety of the recall burden in diverse populations of women

Less hindered ligands give improved catalysts for the nickel catalysed Grignard cross-coupling of aromatic ethers

The authors thanks the EPSRC for funding in the initial stages of this work from EP/J018139/1 and from the DTG.The challenging reaction of unactivated ortho-substituted aromatic ethers with Grignard reagents has been found to be most effectively catalysed using nickel complexes of less sterically hindered ligands. Air stable, cheap, commercially available [NiCl2(PnBu3)2] stands out as an improved catalyst for this type of transformation. The improved results with this catalyst even extend to some couplings of a more activated substrate when examined at higher temperatures and at catalyst loadings down to 0.1 mol%. Unusual induction periods in these latter reactions have been related to the by-product magnesium salts acting as co-catalysts.PostprintPeer reviewe

Manganese catalyzed hydrogenation of enantiomerically pure esters

The authors thank the EPSRC for DTG funding for MBW. The technical support staff at St Andrews are also gratefully acknowledged. The research data supporting this publication can be accessed at: dx.doi.org/10.17630/29308cf7-b6b6- 4b1b-809b-a12fe91b250fA manganese-catalyzed hydrogenation of esters has been accomplished with TON up to 1000, using cheap, environmentally benign, potassium carbonate and simple alcohols as activator and solvent, respectively. The weakly basic conditions lead to good functional group tolerance and enable the hydrogenation of enantiomerically enriched α-chiral esters with essentially no loss of stereochemical integrity.PostprintPeer reviewe

Control via electron count of the competition between magnetism and superconductivity in cobalt and nickel doped NaFeAs

Using a combination of neutron, muon and synchrotron techniques we show how the magnetic state in NaFeAs can be tuned into superconductivity by replacing Fe by either Co or Ni. Electron count is the dominant factor, since Ni-doping has double the effect of Co-doping for the same doping level. We follow the structural, magnetic and superconducting properties as a function of doping to show how the superconducting state evolves, concluding that the addition of 0.1 electrons per Fe atom is sufficient to traverse the superconducting domain, and that magnetic order coexists with superconductivity at doping levels less than 0.025 electrons per Fe atom.Comment: 4 pages, 6 figure