Voltammetry of Immobilized Particles of Cannabinoids

A new electrochemical method for the detection of cannabinoids in food products is proposed. The method is based on the voltammetry of microparticles at a paraffin‐impregnated graphite electrode. In square‐wave voltammetry, in 0.1 M KNO₃ at pH 7, the responses of delta‐9‐tetrahydrocannabinol, cannabinol and cannabidiol consist of a single peak with the maximum at 0.55 V±0.01 V. This peak is ascribed to the electrooxidation of the phenol group to phenoxy radical. In microparticles of hemp and marijuana cannabinoids can be detected in pure drug as well as in the mixture with foreign insoluble powders.     

Flame retardant high oleic sunflower oil‐based thermosetting resins through aza‐ and phospha‐michael additions

Phosphorus‐containing thermosetting resins derived from high oleic sunflower oil were prepared through phospha‐Michael addition of a difunctional secondary phosphine oxide, the 1,3‐bis(phenylphosphino)propane dioxide on the α,β‐unsaturated ketone derived from high oleic acid (ETR). The aim of this approach was to introduce phosphorus and to crosslink the material in one single step. Materials with increasing aromatic content were also prepared by addition 4,4′‐diaminodiphenylmethane and co‐crosslinking through aza‐Michael addition. The kinetics of the phospha and aza‐Michael additions was investigated using the enone derivative of methyl oleate (EO) in presence of BF₃·Et₂O as catalyst and in absence of catalyst at different temperatures. Competitive experiments showed that phospha‐Michael addition proceeds faster than the aza‐Michael addition. The new triglyceride‐based thermosets containing up to 4.2% of P, were characterized and their thermal and flame retardant properties evaluated. Limiting oxygen index values increase from 21.5 for the phosphorus free material up to 38.0 for the final material with 4.2% P content. These results demonstrate that the flame retardant properties of vegetable oil‐based thermosets can be significantly improved by adding covalently bonded phosphorus to the polymer. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

3-Halomethylated cyclic nitronates: synthesis and nucleophilic substitution

A method for the introduction of a halogen atom into the methyl group attached to the C-3 atom of five- and six-membered cyclic nitronates (isoxazoline N-oxides and oxazine N-oxides, respectively) has been studied. The process involves silylation of starting 3-methyl-substituted cyclic nitronates followed by halogenation of the resulting N-(silyloxy)enamines. While five- and six-membered cyclic enamines behave similarly toward elemental bromine and iodine, their reactions with NBS give different products, that were rationalized by stereoelectronic effects. The obtained halogenated nitronates were coupled with various nucleophiles affording new nitronates functionalized at the C-3 position.     

Tetranuclear copper(I) carboxylates: the effect of a stepwise increase in Lewis acidity on solid-state structures and photoluminescence

X-Ray diffraction studies of three aliphatic copper(I) carboxylates revealed a tetranuclear core structure for [Cu(4)(O(2)CCH(2)CH(3))(4)] (1), [Cu(4)(O(2)CCF(3))(O(2)CCH(2)CH(3))(3)] (2), and [Cu(4)(O(2)CCF(2)CF(3))(4)] (3). The effect of a stepwise increase in electrophilicity on solid-state interactions of copper(I) tetramers as well as the implications of structural variations on photoluminescent properties of the above copper(I) propionates have been discussed.     

Hexa­aqua­nickel(II) bis­(hypophosphite)

The structure of hexa­aqua­nickel(II) bis­(hypophosphite), [Ni(H₂O)₆](H₂PO₂)₂, has been determined. The crystals are prismatic. The packing of the Ni and P atoms (not the entire hypophosphite anions) is the same as in the structures of [Co(H₂O)₆](H₂PO₂)₂ and [Co_0.5Ni_0.5(H₂O)₆](H₂PO₂)₂. The Ni^II cations have a pseudo‐face‐centered cubic cell, with cell parameter a 10.216 Å and tetrahedral cavities occupied by P atoms. The Ni^II cation has crystallographically imposed twofold symmetry and has an octahedral coordination sphere consisting of six water O atoms, two of which also lie on the twofold axis. The planes of oppositely coordinated water mol­ecules are in a cross conformation. The geometry of the hypophosphite anion is close to point symmetry mm2. The hypophosphite anions are hydrogen bonded to the coordinated water molecules.     

Stepwise Reduction of Azapentabenzocorannulene

Mono‐ and dianions of 2‐tert‐butyl‐3a²‐azapentabenzo[bc,ef,hi,kl,no]corannulene ( 1 a ) were synthesized by chemical reduction with sodium and cesium metals, and crystallized as the corresponding salts in the presence of 18‐crown‐6 ether. X‐ray diffraction analysis of the sodium salt, [{Na⁺(18‐crown‐6)(THF)₂}₃{Na⁺(18‐crown‐6)(THF)}( 1 a ^2?)₂], revealed the presence of a naked dianion. In contrast, controlled reaction of 1 a with Cs allowed the isolation of singly and doubly reduced forms of 1 a , both forming π‐complexes with cesium ions in the solid state. In [{Cs⁺(18‐crown‐6)}( 1 a ^?)]?THF, asymmetric binding of the Cs⁺ ion to the concave surface of 1 a ^? is observed, whereas in [{Cs⁺(18‐crown‐6)}₂( 1 a ^2?)], two Cs⁺ ions bind to both the concave and convex surfaces of the dianion. The present study provides the first successful isolation and characterization of the reduced products of heteroatom‐containing buckybowl molecules.     

Naphthalene derivatives of a conformationally locked GFP chromophore with large stokes shifts

The active development of fluorescence microscopy requires an increase in the variety of the dyes and their characteristics. Compounds with a large Stokes shift, i.e., a large difference between the positions of the absorption and emission maxima, have attracted the interest of researchers as a tool that can be used for multicolor labeling. One of the known approaches to increase the Stokes shift is the introduction of additional polycyclic fragments. Herein, we report novel derivatives of a conformationally locked GFP chromophore containing the naphthalene ring. The proposed modification leads not only to the enhancement of the Stokes shift up to 100 nm but also leads to the noticeable red-shift of the emission and absorption spectra in contrast with the corresponding derivatives with one benzene ring.     

BF3·OEt2 in alcoholic media,an efficient initiator in the cationic polymerization of phenyl‐1,3‐benzoxazines

3‐Phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine ( m ₁ ) underwent cationic ring opening polymerization using BF₃·OEt₂ in alcoholic solution under mild conditions. The polymerization of m ₁ proceeds through an intermediate hemiaminal ether leading mainly to the formation of polybenzoxazines with diphenylmethane bridges, and not only the classical Mannich‐type ones. During the first stages of the reaction, low‐molecular weight soluble oligomers containing benzoxazine rings are formed. At longer polymerization times, the propagation proceeds conventionally through the phenolic active sites. This polymerization mechanism is extensible to other substituted 3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazines but fails in the case of 3‐alkyl‐3,4‐dihydro‐2H‐1,3‐benzoxazines or when the phenyl group in Position 3 have a substituent in the p‐position. Spectroscopic studies and kinetic experiments using model reactions and deuterium labeled benzoxazines, allow proposing a plausible different polymerization mechanism. These soluble benzoxazine‐containing polymers can be conveniently processed and impregnated on appropriate substrates before underwent crosslinking producing materials with comparable properties to those of conventional bis‐benzoxazines. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5075–5084     

New Triterpenes from Gymnema sylvestre

Phytochemical investigation of the aerial parts of Gymnema sylvestre has led to the isolation of seven new triterpenes, six oleane types ( 5, 7 – 11 ) and a new lupane type ( 12 ), and of the six known analogues 1 – 4, 6 , and 13 . The structures and relative configurations of these compounds were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR spectroscopy and mass spectrometry, and by the comparison of their NMR data with those of related compounds.     

Chromogenic azole diazothiacrown ethers

Azocrown ethers with sulphur atoms and pyrrole or imidazole residue as a part of macrocycle have been synthesised. Their metal complexation abilities in acetonitrile were studied using UV–vis spectrophotometry. The largest spectral changes were observed for both pyrrole- and imidazole-azothiacrown ethers on complexation with Pb^2 + , Cu^2 + , Zn^2 + , Ni^2 + , Co^2 +  and Ag⁺ ions. In the case of alkali and alkaline earth metal ions no spectral changes were found. Preliminary studies of ion-selective membrane electrodes with synthesised ionophores are presented. In the measurement for transition/heavy metal cations, only copper and lead give high responses. X-ray structure of 18-membered pyrrole azothiacrown ether is described.