Recyclable Keggin Heteropolyacids as an Environmentally Benign Catalyst for the Synthesis of New 2-Benzoylamino-N-phenyl-benzamide Derivatives under Microwave Irradiations at Solvent-Free Conditions and the Evaluation of Biological Activity

Preparation of Polyoxometalate-Based Composite by Solidification of Highly Active Cobalt-Containing Polytungstate on Polymeric Ionic Liquid for the Efficient Isolation of Proteinase K

A novel porous polyoxometalate (POM)-based composite (Co₄PW-PDDVAC) was prepared via the solidification of water-soluble polytungstate (Co₄PW) on the polymeric ionic liquid dimethyldodecyl-4-polyethylene benzyl ammonium chloride (PDDVAC) via a cation-exchange reaction. The solidification was confirmed by EDS, SEM, FT-IR, TGA, and so on. The strong covalent coordination and hydrogen-bonding interaction between the highly active Co²⁺ of the Co₄PW and the aspartic acid residues of proteinase K endowed the obtained Co₄PW-PDDVAC composite with excellent proteinase K adsorption properties. Thermodynamic investigations indicate that the adsorption behavior of proteinase K was consistent with the linear Langmuir isothermal model, giving an adsorption capacity as high as 1428 mg g^-1. The Co₄PW-PDDVAC composite was applied in the selective isolation of highly active proteinase K from Tritirachium album Limber crude enzyme fluid.

Synthesis and Characterisation of Monolacunary Keggin Monovanado-deca-tungstophosphate and Its Complexes with Transition Metal Cations

Five new complexes with metal cations (Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, and Cu²⁺) of monolacunary Keggin monovanado-deca-tungstophosphate, K₈[PVW₁₀O₃₉]·15H₂O, have been synthesised. The molar ratio of the combination between metal cations and K₈[PVW₁₀O₃₉]·15H₂O has been established to be 1:1, and its general molecular formulas were found to be: K_n[MPVW₁₀O₃₉(H₂O)]·xH₂O (n = 5 for M = Fe³⁺ and n = 6 for M = Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺). Optimal conditions for complexes' synthesis (pH, temperature, and reaction time) have been determined. The characterisation of K₈[PVW₁₀O₃₉]·15H₂O and of its compounds K_n[MPVW₁₀O₃₉(H₂O)]·xH₂O have been performed using AAS, TG-DTA-DTG, UV-VIS, IR, Raman, and powder XRD methods. In UV spectra, two maximums of absorption were obtained, at 200 and 250 nm, characteristic of Keggin polycondensate compounds. The coordination of cations Ni²⁺, Co²⁺, and Cu²⁺ through oxygen atoms from K₈[PVW₁₀O₃₉]·15H₂O in an octahedron system has been reflected with VIS spectroscopy. All these methods have proved the compositions and structures of K₈[PVW₁₀O₃₉]·15H₂O and K_n[MPVW₁₀O₃₉(H₂O)]·xH₂O, their similarity with other vanadotungstophosphates, and their achievements in the Keggin class. Additionally, all analysis methods have shown an increase in the degree of structural symmetry and the thermal stability of a polyoxoanion complex after attaching metal cations compared to the monolacunary, K₈[PVW₁₀O₃₉]·15H₂O.

A carbene-catalyzed tandem isomerization/cyclisation strategy: an efficient assembly of benzoxazinones

An unprecedented example of NHC-catalyzed tandem isomerization/cyclisation is reported to synthesize benzoxazinones.