New improvements in oligonucleotide synthesis by use of the p-nitrophenylethyl phosphate blocking group and its deprotection by DBU or DBN

Phosphate protection in the phosphotriester approach is improved by the new, versatile p-nitrophenylethyl group due to its stability in the condensation step and its clean removal by DBU and DBN respectively.     

An Alternative to Automatic Titration

Automatic titrators are designed to do exactly what a lab-technician used to do. Much more sophisticated automation of volumetry is possible. Omegaphoresis [3] in buffer-free [2] sample solutions automatically creates a stationary multiple component titration curve or zoned pattern with normalized concentrations of each separated species. An automatic measurement of each zone length yields their quantity. Simultaneous automatic detection of all the zones in a 10–20 component solution in less than 2 minutes, with a precision of ±2%, a required amount of the order of less than one nanomol and a resolution of ±pK < 0.01 replaces acid-base, complexometric, and certain types of redox-titrimetry. An option of the method allows identification of the components as well.     

(PPh4)2[WO2Cl3]2 · 2 CH2Cl2: Synthese,Schwingungsspektrum und Kristallstruktur

(PPh₄)₂[WO₂Cl₃]₂ · 2 CH₂Cl₂. Synthesis, Vibrational Spectrum, and Crystal Structure Depending on the stoichiometry and the solvent, dichloromethane or 1.2-dichloroethane, WO₂Cl₂ reacts with tetraphenylphosphonium chloride affording (PPh₄)₂[WO₂Cl₄] or (PPh₄)₂[WO₂Cl₃]₂, respectively. Both compounds are easily soluble in dichloromethane, from which they can be crystallized under incorporation of two molecules CH₂Cl₂ per formula unit. The crystalline compounds have been characterized by their IR and Raman spectra. According to the X-ray crystal structure analysis, (PPh₄)₂[WO₂Cl₃]₂ · 2 CH₂Cl₂ crystallizes in the triclinic space group P1 with one formula unit per unit cell (986 independent observed reflexions, R = 0.061). Lattice constants: a = 1100.2, b = 1116.9, c = 1238.4 pm, = 69.40, = 80.46 and = 85.62°. The crystals consist of PPh₄^⊕ ions, centrosymmetric [WO₂Cl₃]₂^2? anions and CH₂Cl₂ molecules. In the anions, the tungsten atoms are linked via two oxo bridges with WO distances of 184 and 252 pm. The distorted octahedral coordination around each tungsten atom is completed by three terminal chloro and one terminal oxo ligand (WO bond length 166 pm), the latter being in trans position to the longer WO bridging bond. (PPh₄)₂[WO₂Cl₄] · 2 CH₂Cl₂ also forms triclinic crystals that are isotypic with (PPh₄)₂[WOCl₅] · 2 CH₂Cl₂ and in which the anions must have orientational disorder.     

The Molybdenum Stannide MoSn2

The title compound was prepared by annealing molybdenum powder with an excess of tin. Single-crystals were obtained by dissolving the tin-rich matrix in hydrochloric acid. They are Pauli paramagnetic. The crystal structure was determined from single-crystal X-ray diffractometer data: P6₂22, a = 548.8(1) pm, c = 1417.1(2) pm, Z = 6, R = 0.036 for 18 variable parameters and 389 structure factors. MoSn₂ is only the second representative of the hexagonal Mg₂Ni-type structure. The relation of the structure to the CuAl₂-type is discussed.     

Total synthesis of (±)-Δ9(12)-capnellene via iterative intramolecular type-I-“Magnesium-ene” reactions

The marine triquinane sesquiterpene Δ⁹(¹²)-capnellene ($\text{1}$) was synthesised from 2,2,5-trimethyl-5-hexenal ($\text{2}$) by a sequence of all synthetic operations in 5% overall yield. The key steps 3 → 4 → 5 → 6 involve two intramolecular type-I-“Mg-ene” processes.     

Übergangsmetall-methylen-komplexe: LVI. Organoruthenium-komplexe mit offenkettigen und carbocyclischen alkyliden-brücken: Synthese,konstitution, isomerie,protonierung und thermolytischer abbau

The eighteen new μ-alkylidene ruthenium complexes 5a–r and 5t are very easily and cleanly obtained along the diazoalkane or the hydrazone routes that involve treatment of the dinuclear, metal-metal doubly bonded precursor compound [(η⁵-C₅H₅)Ru(μ-NO)]₂ (3) either with the diazoalkanes oxidizing agent (e.g., MnO₂), with the respective hydrazones. Similarly, sulfur dioxide adds cleanly to the RuRu double bond of 3, thus giving the complex (μ-SO₂)[(η⁵-C₅H₅)Ru(NO)]₂ (5s). Regardless of the nature of the carbene bridge ligands, the dimetallacyclopropanes exhibit, in contrast to their iron analogues, exclusively terminal nitrosyl ligands. cis/trans-Isomerism with predominating amounts of the trans-isomers is observed for the derivatives that display unsymmetrically substituted carbene bridges.Treatment of the μ-methylene- and μ-ethylidene complexes (μ-CH₂)[(η⁵-C₅H₅)Ru(NO)]₂ (5a) and (μ-CHCH₃)[(η⁵-C tetrafluoroboric acid or trifluoromethanesulfonic acid in diethyl ether yields, at ambient temperature, quantitatively the ionic complexes 6a,b and 7a,b, respectively, which were shown by ¹H NMR spectroscopy to contain metal-metal bridging hydrogen functionalities. The reaction of hydrogen bromide with 5a under the same conditions gives the neutral bromo(methyl) complex 6d. This latter compound results from the isolable ionic intermediate of composition [(μ-CH₂)(μ-H){(η⁵C₅H₅)Ru(NO)}₂]⁺Br^? (6c), which reaction stems from the nucleophilicity of the halide ion present in 6c.     

Syntheses of Anthracenones. 1. Sodium Dithionite Reduction of peri-Substituted Anthracenediones

The reaction of peri-substituted anthracenediones with sodium dithionite in dimethylformamide and water has been investigated. The system selectively reduces the carbonyl group flanked by the peri substituents of the anthracenediones to give the corresponding 4,5-disubstituted 9(10H)-anthracenones and thus provides a route to anthracenones which are otherwise difficult to obtain. Many functional groups can be tolerated, the reaction is compatible with the presence of peri alkoxy groups and unsaturated side chains of the starting anthracenediones, and the reduction does not go beyond the anthracenone stage. However, the formation of anthracenones depends on the nature of the peri substituents. No products were obtained from the 1,8-dimethyl-substituted anthracenedione and the parent compound with no substituents.