The formation of open-chain thioesters in the reaction of 2-lithio-2-methyl- and 2-lithio-2-phenyl-1,3-dithiane with chlorodiphenylphosphane followed by oxidation

The unexpected formation of open-chain thioesters (3) and (6) from the reaction of 2-lithio-r-2-t-4-t-6-trimethyl (1-Li) and 2-lithio-r-2-phenyl-t-4-t-6-dimethyl-1,3-dithiane (4-Li), respectively, with chlorodiphenylphosphane followed by oxidation was observed instead of the anticipated gem-derivatives. The X-ray diffraction analysis of (6) and the trapped intermediate (10) confirmed the structure and the proposed mechanism of formation of the open-chain products.     

Geminal approach to vibronic models of superconductivity in crystals. I. The Jahn–Teller effect

Electronic geminals constructed as linear combinations of binary products of site functions are used to formulate a vibronic model of superconductivity in crystals that is based upon the approximation of independent correlated electron pairs obtained variationally from an electron‐pair Hamiltonian and the Jahn–Teller effect. The cyclic symmetry of the system is taken into account and the geminals are sorted into doubly degenerate pairs. The Herzberg–Teller expansion of the pair Hamiltonian in terms of vibrational modes leads directly to the Jahn–Teller effect. A contact transformation of the vibronic Hamiltonian containing only linear terms lowers the energy of the system by a second‐order term associated with the Jahn–Teller stabilization energy. A possible model for superconductivity in solids is proposed on the basis of the Jahn–Teller effect. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Self-association of trimethylsilyl-3,6-di-tert-butyl-o-semiquinone

The reaction of sodium 3,6-di-tert-butyl-o-semiquinolate with Me₃SiCl in THF leads to the formation of 2-(2-trimethylsiloxy-3,6-di-tert-butylphenoxy)-2-trimethylsiloxy-3,6-di-tert-butylcyclohexadien-3,5-one 1. On the basis of IR and UV spectroscopy and analysis of the reaction products, it has been determined that the cyclohexadiene structure 1 is preserved on heating to moderate temperatures or on reaction with water or HCl, but photolysis leads to its decomposition, and so does reaction with metallic sodium or alkali. A scheme of the process is propounded.Institute of Organometallic Chemistry, Russian Academy of Sciences, 603600 Nizhnii Novgorod. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2385–2389, October, 1992.     

Geminal (difluoroamino)nitro compounds

A novel preparative method for the synthesis of geminal (difluoroamino)nitro compounds was developed, The method involves the reaction ofN,N-difluoro-O-fluorosulfonyl- hydroxylamine with the corresponding salts of nitro compounds, Dependences of the yields of (difluoroamino)nitro compounds on the reaction conditions, the nature of the cation in the salts, and the properties of solvents were studied.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11. pp. 2689–2692, November, 1996.     

Piano-Stool Ruthenium N-Heterocyclic Carbene Complexes for gem-Specific Catalytic Dimerization of Terminal Alkynes

A series of piano-stool Ru−NHC (NHC=N-heterocyclic carbene) complexes have been prepared and characterized. The NHC ligands used herein have varying wingtip groups, showing the impact of steric congestion on the selectivity for the catalytic dimerization of terminal alkynes.     

唑来膦酸及其有关化合物的反相离子对高效液相色谱分离

采用反相离子对高效液相色谱法研究了唑来膦酸及其有关化合物的色谱分析与分离方法。优化的分离条件：以Hypersil C8柱为固定相,以甲醇-5 mmol/L磷酸二氢钠缓冲液(含6 mmol/L四丁基溴化铵溶液,用氢氧化钠溶液调节pH至7.0)(体积比为20∶80)为流动相,等度洗脱,流速为1.0 mL/min,紫外检测波长为220 nm,柱温为室温。在该色谱条件下,唑来膦酸与有关化合物(包括其合成过程中残余的原料咪唑乙酸和其他氧化分解产物)的分离良好,与保留时间最接近的杂质峰的分离度大于2.5。该方法不需进     

Influence of steric and intramolecular inductive effects on the variable trends in R-X (R=Alkyl) bond dissociation energy

The question “why are the variation trends of R-X bond dissociation energy different?” is answered. The R-X bond dissociation energy (BDE) may be influenced by three main factors: the C-X intrinsic bond energy, the 1,3 geminal repulsion, and the intramolecular charge-induced dipole. In the presence of atom X, the variation trend of BDE in R-X (R= Me, Et, i-Pr, t-Bu) is dominated by two factors, the 1,3 geminal repulsion and the intramolecular charge-induced dipole. The former decreases the R-X BDE, and the latter either increases or decreases the R-X BDE. For the series of R-X with the R-C bond (such as R-Me, R-CH == CH², R-C≡CH, and R-CN), the 1,3 geminal repulsion decreases the R-X BDE, and the variation trends of R-C BDE decrease from Me to t-Bu. As regards the series of R-X (such as R-H, R-BH², and R-SiH²) in which the electronegativity of atom X is smaller than that of the carbon atom, the above two factors decrease the R-X BDE, and the variation trends of the R-X BDE decrease from Me to t-Bu. As to the series of R-X (such as R-F, R-OH, R-Cl, R-Br, R-I, and R-NH²) in which the electronegativity of atom X is larger than that of the carbon atom, the 1,3 geminal repulsion decreases the R-X BDE, while the intramolecular charge-induced dipole increases the R-X BDE. In this case, the variation trends of R-X BDE depend on the competition of the two factors. As a result, some of them (e. g., R-F, R-OH) increase from Me to t-Bu, some (e. g., R-I) decrease from Me to t-Bu, and some (e. g., R-Br) change very little.     

Tracking Bisphosphonates through a 20 mm Thick Porcine Tissue by Using Surface-Enhanced Spatially Offset Raman Spectroscopy

Track it down: A recognized surface-enhanced Raman scattering (SERS) nanotag signal was monitored from a thin, dispersed layer of bisphosphonate-functionalized nanotags on a bone sample, through a 20?mm thick specimen of porcine muscle tissue by surface-enhanced spatial offset Raman spectroscopy (SESORS; see picture). The result demonstrates the great potential for non-invasive in?vivo bisphosphonate drug tracking.