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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)

   Abstract 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. Spatial and temporal variability in summertime dissolved carbon dioxide and methane in temperate ponds and shallow lakes

   https://doi.org/10.1002/lno.12362  

   Ray, Nicholas E.; Holgerson, Meredith A.; Andersen, Mikkel Rene; Bikše, Jānis; Bortolotti, Lauren E.; Futter, Martyn; Kokorīte, Ilga; Law, Alan; McDonald, Cory; Mesman, Jorrit P.; et al (May 2023, Limnology and Oceanography)

   Abstract Small waterbodies have potentially high greenhouse gas emissions relative to their small footprint on the landscape, although there is high uncertainty in model estimates. Scaling their carbon dioxide (CO₂) and methane (CH₄) exchange with the atmosphere remains challenging due to an incomplete understanding and characterization of spatial and temporal variability in CO₂and CH₄. Here, we measured partial pressures of CO₂(pCO₂) and CH₄(pCH₄) across 30 ponds and shallow lakes during summer in temperate regions of Europe and North America. We sampled each waterbody in three locations at three times during the growing season, and tested which physical, chemical, and biological characteristics related to the means and variability ofpCO₂andpCH₄in space and time. Summer means ofpCO₂andpCH₄were inversely related to waterbody size and positively related to floating vegetative cover;pCO₂was also positively related to dissolved phosphorus. Temporal variability in partial pressure in both gases weas greater than spatial variability. Although sampling on a single date was likely to misestimate mean seasonalpCO₂by up to 26%, mean seasonalpCH₄could be misestimated by up to 64.5%. Shallower systems displayed the most temporal variability inpCH₄and waterbodies with more vegetation cover had lower temporal variability. Inland waters remain one of the most uncertain components of the global carbon budget; understanding spatial and temporal variability will ultimately help us to constrain our estimates and inform research priorities. 

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3. Methane Carboxylation Using Electrochemically Activated Carbon Dioxide

   https://doi.org/10.1002/anie.202305568  

   Yuan, Yucheng; Zhang, Yuhan; Li, Haoyi; Fei, Muchun; Zhang, Hongna; Santoro, John; Wang, Dunwei (May 2023, Angewandte Chemie International Edition)

   Abstract Direct synthesis of CH₃COOH from CH₄and CO₂is an appealing approach for the utilization of two potent greenhouse gases that are notoriously difficult to activate. In thisCommunication, we report an integrated route to enable this reaction. Recognizing the thermodynamic stability of CO₂, our strategy sought to first activate CO₂to produce CO (through electrochemical CO₂reduction) and O₂(through water oxidation), followed by oxidative CH₄carbonylation catalyzed by Rh single atom catalysts supported on zeolite. The net result was CH₄carboxylation with 100 % atom economy. CH₃COOH was obtained at a high selectivity (>80 %) and good yield (ca. 3.2 mmol g⁻¹_catin 3 h). Isotope labelling experiments confirmed that CH₃COOH is produced through the coupling of CH₄and CO₂. This work represents the first successful integration of CO/O₂production with oxidative carbonylation reaction. The result is expected to inspire more carboxylation reactions utilizing preactivated CO₂that take advantage of both products from the reduction and oxidation processes, thus achieving high atom efficiency in the synthesis. 

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4. Synthesis of Tris[2‐(dimethylamino)ethyl]amine with Regiospecific Deuterium Labels

   https://doi.org/10.1002/slct.202300053  

   Sobieski, Julian; Ruzhylo, Illia; Szczepaniak, Grzegorz; Gorczyński, Adam; Matyjaszewski, Krzysztof; Manoury, Eric; Poli, Rinaldo (February 2023, ChemistrySelect)

   Abstract Simple synthetic routes to regioselectively deuterated tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) variants are described. Imine formation with formaldehyde‐d₂from tris(2‐aminoethyl)amine (TREN) and subsequent reductions with NaBD₄afforded N[CH₂CH₂N(CD₃)₂]₃ord₁₈‐Me₆TREN in 79 % yield. A trisubstitution protocol from 2‐bromo‐N,N‐dimethylacetamide and ammonium carbonate and subsequent reduction of the N(CH₂CONMe₂)₃intermediate by lithium aluminum deuteride has afforded N[CH₂CD₂N(CH₃)₂]₃or (d₆‐arm)‐Me₆TREN in three steps and 52 % overall yield. A similar protocol from 2‐bromo‐N,N‐dimethyl‐d₂‐acetamide, obtained in two steps fromd₄‐acetic acid, with reduction of the N(CD₂CONMe₂)₃intermediate by lithium aluminum hydride has afforded N[CD₂CH₂N(CH₃)₂]₃or (d₆‐cap)‐Me₆TREN in four steps and 13 % overall yield from CD₃COOD. 

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5. Competition between chalcogen and halogen bonding assessed through isostructural species

   https://doi.org/10.1107/S205322962201052X  

   De Silva, Viraj; Magueres, Pierre Le; Averkiev, Boris B.; Aakeröy, Christer B. (December 2022, Acta Crystallographica Section C Structural Chemistry)

   The amino group of 2-amino-5-(4-halophenyl)-1,3,4-chalcogenadiazole has been replaced with bromo/iodo substituents to obtain a library of four compositionally related compounds. These are 2-iodo-5-(4-iodophenyl)-1,3,4-thiadiazole, C₈H₄I₂N₂S, 2-bromo-5-(4-bromophenyl)-1,3,4-selenadiazole, C₈H₄Br₂N₂Se, 2-bromo-5-(4-iodophenyl)-1,3,4-selenadiazole, C₈H₄BrIN₂Se, and 2-bromo-5-(4-iodophenyl)-1,3,4-thiadiazole, C₈H₄BrIN₂S. All were isostructural and contained bifurcated Ch...N (Ch is chalcogen) andX...X(Xis halogen) interactions forming a zigzag packing motif. The noncovalent Ch...N interaction between the chalcogen-bond donor and the best-acceptor N atom appeared preferentially instead of a possible halogen bond to the same N atom. Hirshfeld surface analysis and energy framework calculations showed that, collectively, a bifurcated chalcogen bond was stronger than halogen bonding and this is more structurally influential in this system. 

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