Reaction of difluorocarbene with anions from amides and oximes: Synthesis of N-difluoromethyl substituted amides, O-difluoromethylimidates or O-difluoromethyl substituted oximes under phase-transfer catalysis conditions

N-Aryl substituted amides react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst in benzene (phase-transfer catalysis, PTC), affording mixtures of N- and O-difluoromethyl substituted derivatives. Amide anions are involved in this process. The reaction carried out with oximes gives O-difluoromethyl oxime ethers.     

Transalkylation of alkyl aryl sulfides with alkylating agents

The reaction of methyl iodide with tert-butylphenylsulfide in DMF leads to a transalkylation that produces methylphenylsulfide. This transalkylation reaction was further studied by ¹H NMR spectroscopy. The polarity of the solvent, the electron density on the sulfur atom, and the strength of the alkylating agent (MeI, EtI, BuI, dimethyl sulfate, or dimethyl carbonate) played important roles in the reaction. The suggested mechanism of the reaction involves the formation of a dialkyl aryl sulfonium salt that subsequently eliminates the radical. This mechanism was supported by the observation of higher conversion rates for compounds with more branched alkyl groups on the sulfur atom, which may lead to the formation of more stable radicals.     

Novel copper complexes based on the thiocyanate bridge - Synthesis, X-ray studies and magnetic properties

Three novel compounds {[Cu(bpzm)(SCN)][Cu(bpzm)(MeOH)][Cu(SCN)₄]}_n (1a), {[Cu₂(bpzm)₂(μ-SCN)(SCN)₃]}_n (1b) and [Cu₂(μ-SCN)₂(SCN)₂(dpa)₂] (2) have been obtained in one-step self-assembly reaction of copper dichloride, a suitable N-N ligand (bis(pyrazol-1-yl)methane and 2,2′-dipyridylamine) and ammonium thiocyanate. For the reaction involving bis(pyrazol-1-yl)methane, an unprecedented in situ reduction of some Cu(II) ions to Cu(I) has been observed. The compound {[Cu(bpzm)(SCN)][Cu(bpzm)(MeOH)][Cu(SCN)₄]}_n (1a) belongs to a relatively scarce group of mixed-valence Cu^II/Cu^I coordination polymers with interesting polymeric architecture. It creates infinite two-dimensional structure consisting of layers extending along crystallographic plane (0 0 1), in which the cations [Cu^II(bpzm)(SCN)]⁺ and [Cu^II(bpzm)(MeOH)]²⁺ are connected by ions [Cu^I(SCN)₄]³⁻ through single end-to-end thiocyanato bridges. Structure 1b consists two crystallographically independent chains. The chain A has a zig-zag form and extends along the crystallographic direction [0 0 1], whereas the second chain is linear and runs along the crystallographic direction [0 1 0]. The structure 2 consists of dinuclear [Cu₂(dpa)₂(μ-SCN)₂(SCN)₂] units. Variable-temperature magnetic susceptibility measurements show very weak antiferromagnetic interactions between the paramagnetic centres Cu(II) centers inside the crystal lattices of three novel compounds.     

Sweet ionic liquids-cyclamates: Synthesis, properties, and application as feeding deterrents

In this paper, we show that sweet quaternary ammonium, pyridinium, and imidazolium cyclamates are cheap, thermally stable, surface and biologically active ionic liquids, with potential application as feeding deterrents.     

Phase behavior of the quasiternary system N-methylmorpholine-N-oxide,water, and cellulose

The crystallization and melting behavior of the system N-methylmorpholine-N-oxide (MMNO)–H₂O–cellulose has been studied by differential scanning calorimetry, optical and electron microscopy, and x-ray scattering. The phase diagram of the MMNO–H₂O solvent system is reported up to a water content of 28% w/w. MMNO forms two crystalline hydrates, namely a monohydrate (13,3% w/w H₂O) and a hydrate comprising five molecules of crystal water per two MMNO molecules (28% w/w H₂O), which melts at 78°C and 39°C, respectively. The melting points of the various diluent crystals are strongly depressed in the presence of cellulose. For example, the solvent liquidus curve in the quasibinary system MMNO.1H₂O–cellulose can be described very well using the simple Flory–Huggins expression with an interaction parameter χ = ?3. Finally, the MMNO-rich part of the melting point/composition diagram of the quasiternary MMNO–H₂O–cellulose system is constructed and discussed.     

Discrimination in metal-ion binding to RNA dinucleotides with a non-bridging oxygen or sulfur in the phosphate diester link

Replacement of a non-bridging oxygen in the phosphate diester bond by a sulfur has become quite popular in nucleic acid research and is often used as a probe, for example, in ribozymes, where the normally essential Mg(2+) is partly replaced by a thiophilic metal ion to reactivate the system. Despite these widely applied rescue experiments no detailed studies exist quantifying the affinity of metal ions to such terminal sulfur atoms. Therefore, we performed potentiometric pH titrations to determine the binding properties of pUp((S))U(3-) towards Mg(2+), Mn(2+), Zn(2+), Cd(2+), and Pb(2+), and compared these data with those previously obtained for the corresponding pUpU(3-) complexes. The primary binding site in both dinucleotides is the terminal phosphate group. Theoretically, also the formation of 10-membered chelates involving the terminal oxygen or sulfur atoms of the (thio)phosphate bridge is possible with both ligands. The results show that Mg(2+) and Mn(2+) exist as open (op) isomers binding to both dinucleotides only at the terminal phosphate group. Whereas Cd(pUpU)(-) only exists as Cd(pUpU)(-)(op), Cd(pUp((S))U)(-) is present to about 64 % as the S-coordinated macrochelate, Cd(pUp((S))U)(-)(cl/PS). Zn(2+) forms with pUp((S))U(3-) three isomeric species, that is, Zn(pUp((S))U)(-)(op), Zn(pUp((S))U)(-)(cl/PO), and Zn(pUp((S))U)(-)(cl/PS), which occur to about 33, 12 (O-bound), and 55 %, respectively. Pb(2+) forms the 10-membered chelate with both nucleotides involving only the terminal oxygen atoms of the (thio)phosphate bridge, that is, no indication of S binding was discovered in this case. Hence, Zn(2+) and Cd(2+) show pronounced thiophilic properties, whereas Mg(2+), Mn(2+), and Pb(2+) coordinate to the oxygen, macrochelate formation being of relevance with Pb(2+) only.