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1. A Nontemplated Route to Macrocyclic Dibridgehead Diphosphorus Compounds: Crystallographic Characterization of a “Crossed‐Chain” Variant of in / out Stereoisomers

   https://doi.org/10.1002/asia.201800739  

   Kharel, Sugam ; Jia, Tiezheng ; Bhuvanesh, Nattamai ; Reibenspies, Joseph H. ; Blümel, Janet ; Gladysz, John A. ( August 2018 , Chemistry – An Asian Journal)

   Reactions of (O=)PH(OCH₂CH₃)₂and BrMg(CH₂)_mCH=CH₂(4.9–3.2 equiv;m=4 (a), 5 (b), 6 (c)) give the dialkylphosphine oxides (O=)PH[(CH₂)_mCH=CH₂]₂(2 a–c; 77–81 % after workup), which are treated with NaH and then α,ω‐dibromides Br(CH₂)_nBr (0.49–0.32 equiv;n=8 (a′), 10 (b′), 12 (c′), 14 (d′)) to yield the bis(trialkylphosphine oxides) [H₂C=CH(CH₂)_m]₂P(=O)(CH₂)_n(O=)P[(CH₂)_mCH=CH₂]₂(3 ab′,3 bc′,3 cd′,3 ca′; 79–84 %). Reactions of3 bc′and3 ca′with Grubbs’ first‐generation catalyst and then H₂/PtO₂afford the dibridgehead diphosphine dioxides(4 bc′,4 ca′; 14–19 %,n′=2m+2);³¹P NMR spectra show two stereoisomeric species (ca. 70:30). Crystal structures of two isomers of the latter are obtained,out,out‐4 ca′and a conformer ofin,out‐4 ca′that features crossed chains, such that the (O=)P vectors appearout,out. Whereas4 bc′resists crystallization, a byproduct derived from an alternative metathesis mode, (CH₂)₁₂P(=O)(CH₂)₁₂(O=)P(CH₂)₁₂, as well as3 ab′and3 bc′, are structurally characterized. The efficiencies of other routes to dibridgehead diphosphorus compounds are compared.

    

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2. Temporal trends in molecular markers of drug resistance in Plasmodium falciparum in human blood and profiles of corresponding resistant markers in mosquito oocysts in Asembo, western Kenya

   https://doi.org/10.1186/s12936-022-04284-6  

   Zhou, Zhiyong ; Gimnig, John E. ; Sergent, Sheila B. ; Liu, Ying ; Abong’o, Bernard ; Otieno, Kephas ; Chebore, Winnie ; Shah, Monica P. ; Williamson, John ; ter Kuile, Feiko O. ; et al ( September 2022 , Malaria Journal)

   Over the last two decades, the scale-up of vector control and changes in the first-line anti-malarial, from chloroquine (CQ) to sulfadoxine-pyrimethamine (SP) and then to artemether-lumefantrine (AL), have resulted in significant decreases in malaria burden in western Kenya. This study evaluated the long-term effects of control interventions on molecular markers ofPlasmodium falciparumdrug resistance using parasites obtained from humans and mosquitoes at discrete time points.

   Dried blood spot samples collected in 2012 and 2017 community surveys in Asembo, Kenya were genotyped by Sanger sequencing for markers associated with resistance to SP (Pfdhfr, Pfdhps), CQ, AQ, lumefantrine (Pfcrt, Pfmdr1)and artemisinin (Pfk13).Temporal trends in the prevalence of these markers, including data from 2012 to 2017 as well as published data from 1996, 2001, 2007 from same area, were analysed. The same markers from mosquito oocysts collected in 2012 were compared with results from human blood samples.

   The prevalence of SPdhfr/dhpsquintuple mutant haplotype C₅₀I₅₁R₅₉N₁₀₈I₁₆₄/S₄₃₆G₄₃₇E₅₄₀A₅₈₁A₆₁₃increased from 19.7% in 1996 to 86.0% in 2012, while an increase in the sextuple mutant haplotype C₅₀I₅₁R₅₉N₁₀₈I₁₆₄/H₄₃₆G₄₃₇E₅₄₀A₅₈₁A₆₁₃containingPfdhps-436H was found from 10.5% in 2012 to 34.6% in 2017. ResistantPfcrt-76 T declined from 94.6% in 2007 to 18.3% in 2012 and 0.9% in 2017. MutantPfmdr1-86Y decreased across years from 74.8% in 1996 to zero in 2017, mutantPfmdr1-184F and wildPfmdr1-D1246 increased from 17.9% to 58.9% in 2007 to 55.9% and 90.1% in 2017, respectively.Pfmdr1haplotype N₈₆F₁₈₄S₁₀₃₄N₁₀₄₂D₁₂₄₆ increased from 11.0% in 2007 to 49.6% in 2017. No resistant mutations inPfk13were found. Prevalence ofPfdhps-436H was lower while prevalence ofPfcrt-76 T was higher in mosquitoes than in human blood samples.

   This study showed an increased prevalence ofdhfr/dhpsresistant markers over 20 years with the emergenceof Pfdhps-436H mutant a decade ago in Asembo. The reversal ofPfcrtfrom CQ-resistant to CQ-sensitive genotype occurred following 19 years of CQ withdrawal. NoPfk13markers associated with artemisinin resistance were detected, but the increased haplotype ofPfmdr1N₈₆F₁₈₄S₁₀₃₄N₁₀₄₂D₁₂₄₆was observed. The differences in prevalence ofPfdhps-436H andPfcrt-76 T SNPs between two hosts and the role of mosquitoes in the transmission of drug resistant parasites require further investigation.

    

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3. Sustainable polyacetals from erythritol and bioaromatics

   https://doi.org/10.1002/app.44089  

   Rostagno, Mayra ; Price, Erik J. ; Pemba, Alexander G. ; Ghiriviga, Ion ; Abboud, Khalil A. ; Miller, Stephen A. ( July 2016 , Journal of Applied Polymer Science)

   The polymerization of biorenewable molecules to polymers with hydrolyzable main‐chain functionality is one approach to identifying sustainable replacements for common, environmentally unsound packaging plastics. Bioaromatic polyacetals were synthesized via acid‐catalyzed acetal formation from dialdehydes and tetraols. Ethylene linked dialdehyde monomersVVandSSwere constructed from bioaromatics vanillin and syringaldehyde, respectively. Tetraol monomers included biogenic erythritol (E), along with pentaerythritol (P), and ditrimethylolpropane (D). Four copolymer series were prepared with varying tetraol content:E/P‐VV;E/D‐VV;E/P‐SS; andE/D‐SS. Number average molecular weights (M_n) ranged from 1,400 to 27,100 Da. Generally, the copolymerization yields were inversely proportional to the feed fraction of erythritol (E), implying that tetraolsPandDreact more readily. The materials were typically amorphous and exhibited glass transition temperatures (T_g) ranging from 57 to 159 °C, suitably mimicking theT_gvalues of several commodity plastics. The syringaldehyde‐based copolymers exhibited a higherT_grange (71–159 °C) than the vanillin‐based copolymers (57–110 °C). Accelerated degradation studies in aqueous HCl (3M, 6M, concentrated) over 24 h showed that degradation (M_ndecrease) was proportional to the acid concentration. A one‐year degradation study ofE50/D50‐SS(from 50% feed of erythritol) in seawater, deionized water, tap water, or pH 5 buffer showed noM_ndecrease; but in pH 1 buffer, the decrease was 40% (18,800 to 11,200). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 44089.

    

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4. Macrocyclic Complexes Derived from Four cis ‐L 2 Pt Corners and Four Butadiynediyl Linkers; Syntheses, Electronic Structures, and Square versus Skew Rhombus Geometries

   https://doi.org/10.1002/chem.202100305  

   Collins, Brenna K. ; Clough Mastry, Melissa ; Ehnbom, Andreas ; Bhuvanesh, Nattamai ; Hall, Michael B. ; Gladysz, John A. ( June 2021 , Chemistry – A European Journal)

   The dialkyl malonate derived 1,3‐diphosphines R₂C(CH₂PPh₂)₂(R=a, Me;b, Et;c,n‐Bu;d,n‐Dec;e, Bn;f,p‐tolCH₂) are combined with (p‐tol₃P)₂PtCl₂ortrans‐(p‐tol₃P)₂Pt((C≡C)₂H)₂to give the chelatescis‐(R₂C(CH₂PPh₂)₂)PtCl₂(2 a–f, 94–69 %) orcis‐(R₂C(CH₂PPh₂)₂)Pt((C≡C)₂H)₂(3 a–f, 97–54 %). Complexes3 a–dare also available from2 a–dand excess 1,3‐butadiyne in the presence of CuI (cat.) and excess HNEt₂(87–65 %). Under similar conditions,2and3react to give the title compounds [(R₂C(CH₂PPh₂)₂)[Pt(C≡C)₂]₄(4 a–f; 89–14 % (64 % avg)), from which ammonium salts such as the co‐product [H₂NEt₂]⁺Cl⁻are challenging to remove. Crystal structures of4 a,bshow skew rhombus as opposed to square Pt₄geometries. The NMR and IR properties of4 a–fare similar to those of mono‐ or diplatinum model compounds. However, cyclic voltammetry gives only irreversible oxidations. As compared to mono‐platinum or Pt(C≡C)₂Pt species, the UV‐visible spectra show much more intense and red‐shifted bands. Time dependent DFT calculations define the transitions and principal orbitals involved. Electrostatic potential surface maps reveal strongly negative Pt₄C₁₆cores that likely facilitate ammonium cation binding. Analogous electronic properties of Pt₃C₁₂and Pt₅C₂₀homologs and selected equilibria are explored computationally.

    

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5. Isolation of an Elusive Phosphametallacyclobutadiene and Its Role in Reversible Carbon−Carbon Bond Cleavage

   https://doi.org/10.1002/anie.202203073  

   Jakhar, Vineet K. ; Esper, Alec M. ; Ghiviriga, Ion ; Abboud, Khalil A. ; Ehm, Christian ; Veige, Adam S. ( June 2022 , Angewandte Chemie International Edition)

   The reactivity of phosphaalkynes, the isolobal and isoelectronic congeners to alkynes, with metal alkylidyne complexes is explored in this work. Treating the tungsten alkylidyne [^tBuOCO]W≡C^tBu(THF)₂(1) with phosphaalkyne (10) results in the formation of [O₂C(^tBuC=)W{η²‐(P,C)−P≡C−Ad}(THF)] (13‐^tBu_THF) and [O₂C(AdC=)W{η²‐(P,C)−P≡C−^tBu}(THF)] (13‐Ad_THF); derived from the formal reductive migratory insertion of the alkylidyne moiety into a W−C_arenebond. Analogous to alkyne metathesis, a stable phosphametallacyclobutadiene complex [^tBuOCO]W[κ²‐C(^tBu)PC(Ad)] (14) forms upon loss of THF from the coordination sphere of either13‐^tBu_THFor13‐Ad_THF. Remarkably, the C−C bonds reversibly form/cleave with the addition or removal of THF from the coordination sphere of the formal tungsten(VI) metal center, permitting unprecedented control over the transformation of a tetraanionic pincer to a trianionic pincer and back. Computational analysis offers thermodynamic and electronic reasoning for the reversible equilibrium between13‐^tBu/Ad_THFand14.

    

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