Reagents for Selective Fluoromethylation: A Challenge in Organofluorine Chemistry

The introduction of a monofluoromethyl moiety has undoubtedly become a very important area of research in recent years. Owing to the beneficial properties of organofluorine compounds, such as their metabolic stability, the incorporation of the CH₂F group as a bioisosteric substitute for various functional groups is an attractive strategy for the discovery of new pharmaceuticals. Furthermore, the monofluoromethyl unit is also widely used in agrochemistry, in pharmaceutical chemistry, and in fine chemicals. The problems associated with climate change and the growing need for environmentally friendly industrial processes mean that alternatives to the frequently used CFC and HFBC fluoromethylating agents (CH₂FCl and CH₂FBr) are urgently needed and also required by the Montreal Protocol. This has recently prompted many researchers to develop alternative fluoromethylation agents. This Minireview summarizes both the classical and new generation of fluoromethylating agents. Reagents that act via electrophilic, nucleophilic, and radical pathways are discussed, in addition to their precursors.     

WO3 thermodynamic properties at 80–1256 K revisited

Journal of Thermal Analysis and Calorimetry - Thermodynamic properties (heat capacity Cp, entropy S°, enthalpy change ΔH° and reduced Gibbs energy ΔΦ°) of crystalline...     

Cobalt‐Catalyzed Cross‐Coupling of Functionalized Alkylzinc Reagents with (Hetero)Aryl Halides

A combination of 10 % CoCl₂ and 20 % 2,2′‐bipyridine ligands enables cross‐coupling of functionalized primary and secondary alkylzinc reagents with various (hetero)aryl halides. Couplings with 1,3‐ and 1,4‐substituted cycloalkylzinc reagents proceeded diastereoselectively leading to functionalized heterocycles with high diastereoselectivities of up to 98:2. Furthermore, alkynyl bromides react with primary and secondary alkylzinc reagents providing the alkylated alkynes.     

Controlling Gas Selectivity in Molecular Porous Liquids by Tuning the Cage Window Size

Control of pore window size is the standard approach for tuning gas selectivity in porous solids. Here, we present the first example where this is translated into a molecular porous liquid formed from organic cage molecules. Reduction of the cage window size by chemical synthesis switches the selectivity from Xe‐selective to CH₄‐selective, which is understood using ¹²⁹Xe, ¹H, and pulsed‐field gradient NMR spectroscopy.     

Purification of Hydrogen from CO with Cu/ZSM-5 Adsorbents

The transition to a hydrogen economy requires the development of cost-effective methods for purifying hydrogen from CO. In this study, we explore the possibilities of Cu/ZSM-5 as an adsorbent for this purpose. Samples obtained by cation exchange from aqueous solution (AE) and solid-state exchange with CuCl (SE) were characterized by in situ EPR and FTIR, H₂-TPR, CO-TPD, etc. The AE samples possess mainly isolated Cu²⁺ cations not adsorbing CO. Reduction generates Cu⁺ sites demonstrating different affinity to CO, with the strongest centres desorbing CO at about 350 °C. The SE samples have about twice higher Cu/Al ratios, as one H⁺ is exchanged with one Cu⁺ cation. Although some of the introduced Cu⁺ sites are oxidized to Cu²⁺ upon contact with air, they easily recover their original oxidation state after thermal treatment in vacuum or under inert gas stream. In addition, these Cu⁺ centres regenerate at relatively low temperatures. It is important that water does not block the CO adsorption sites because of the formation of Cu⁺(CO)(H₂O)_x complexes. Dynamic adsorption studies show that Cu/ZSM-5 selectively adsorbs CO in the presence of hydrogen. The results indicate that the SE samples are very perspective materials for purification of H₂ from CO.     

Sulfur derivatives of 3-methyl-5-phenyl-1,2,4,3-triazaphosphole

The triazaphosphole 1 adds sulfur along with HCl or H₂S to yield, respectively, the dihydrotriazaphosphole thiochloride 4 and sesquisulfide 5 (two diastereomers). In pyridine solution, 1 adds sulfur alone to yield the trimer of a triazaphosphole monosulfide 7 . Its central cyclotriphosphazane trisulfide ring has a trans structure and a boat conformation.     

1, 3-azaphospholo[5, 1-b]thiazolines and benzothiazoles

The title compounds 3 and 7 are novel heterocyclic systems incorporating two-coordinate phosphorus. They are obtained in reasonable to good yields from the condensation of suitable 2-ethyl-3-alkylthiazolinium and -benzothiazolium bromides 2 and 6 with phosphorus trichloride in the presence of triethylamine in an aprotic solvent. Intermediate dichlorophosphino-substituted N-ylides can be observed or isolated in some cases. From a 2-methyl-3-alkylthiazolinium bromide ( 2a ), a 1-(dichlorophosphino) substituted 1, 3-azaphospholo[5,1-b]thiazoline ( 4 ) was obtained. The chemical shift of the two-coordinate phosphorus in 1,3-azaphosphole derivatives clearly reflects the influence of the heterocyclic system annulated to its 1,5-bond and of the substituents in its 2-and 4-positions.     

Copper(II)–lanthanide(III) 15-metallacrown-5 complexes based on pyrazinohydroxamic acid as new multiple-binding pentagonal platforms with Lewis amphoteric nature

Reaction of copper(II) acetate, lanthanium(III) or gadolinium(III) nitrate (1/5 equiv.) with pyrazinohydroxamic acid (H₂Pyzha) in DMF led to a series of new heterobimetallic 15-metallacrown-5 complexes. In a MeOH/H₂O solution the complexes exist as molecular unassociated metallacrowns. In solid state their structures are more complicated as it has been confirmed by X-ray analysis: discrete molecular metallacrowns [Gd(NO₃)₂{Cu(pyzha)}₅(DMF)₄(NO₃)] · 0.5C₆H₆ · H₂O (1), [Gd(NO₃)₂{Cu(pyzha)}₅(DMF)₅](NO₃) · 1.5DMF · 0.5H₂O (2), [La(NO₃)₂{Cu(pyzha)}₅(DMF)₅]NO₃ · 1.5DMF · 2C₆H₆ (3) are solvates, whereas compound [{La(NO₃)₂{Cu(pyzha)}₅(DMF)₅}₂(μ²-NO₃)](NO₃) · 3DMF (4) is a dimer, where μ-bridged nitrate links two copper centres of the adjacent metallamacrocycles. Complex [Gd(NO₃)₂{Cu(pyzha)}₅(DMF)₂(H₂O)(NO₃)] · CH₂Cl₂ · DMF (5) self-associates into a polymer chain by means of one pyrazine moiety and the copper ring atom. Reaction of the molecular metallacrowns with excess of inorganic salts CdBr₂ or Cu(OAc)₂ proceeds as anion methathesis process affording heteroanionic metallacrowns: molecular [Gd(NO₃)₂{Cu(pyzha)}₅(DMF)₅] [Gd(NO₃)₂{Cu(pyzha)}₅(DMF)₄(H₂O)][CdBr₄] · 1.5DMF (6), and 3D hydrogen bonded polymer [La(μ²-OAc)(H₂O)₃{Cu(pyzha)}₅ (H₂O)₄(NO₃)](NO₃) · 4H₂O (7).