Synthesis of substituted thienopyrimidine-4-ones

The parallel solution-phase synthesis of more than 3000 substituted thienopyrimidin-4-ones has been accomplished. Key reactions include assembly of the 2-thioxopyrimidin-4-one ring by condensation of isomeric aminothiophenecarboxylates or their appropriate reactive derivatives (isothiocyanates or dithiocarbamates) with the corresponding isothiocyanates or amines. The libraries from libraries were then obtained in good yields and purities using solution-phase alkylation and acylation methodologies. Simple manual techniques for parallel reactions using special CombiSyn synthesizers were coupled with easy purification procedures (crystallization from the reaction mixtures) to give high-purity final products. The scope and limitations of the developed approach are discussed.     

L^p -uniqueness for Dirichlet operators with singular potentials

We study the problem of strong uniqueness in L^p for the Dirichlet operator perturbed by a singular complex-valued potential. First we construct the generator -H_p of a C₀-semigroup in L^p, with H_p extending the restriction of the perturbed Dirichlet operator to the set of smooth functions. The corresponding sesquilinear form in L² is not assumed to be sectorial. Then we reveal sufficient conditions on the logarithmic derivative # of the measure rdx \rho dx and the potential q which ensure that -H_p is the only extension of D+b·?-q \upharpoonright_C0^￥ \Delta +\beta \cdot \nabla -q \upharpoonright_{C_0^{\infty}} which generates a C₀-semigroup on L^p. The method of a priori estimates of solutions to corresponding differential equations is employed.     

利用飞秒双光子光电子发射研究GaAs(100)的自旋动力学过程

超短激光技术的发展为研究材料中的超快光动方学过程提供了重要的实验手段，也使得人们 能够更为深入地研究电子的自旋动力学行为.GaAs(100)表面由于费米钉扎而会导致能带弯曲 ，位于该区域的电子及其自旋特性将会明显不同于体相材料中的情况.利用时间分辨和自旋 分辨的双光子光电子发射技术研究了p型掺杂GaAs(100)表面的电子极化动力学过程.结果表 明，由费米钉扎而引起的能带弯曲明显影响电子的自旋弛豫过程，从实验上观察到了GaAs(1 00)表面能带弯曲区域的电子自旋翻转时间存在近2个量级的差异(从几纳秒到几十皮秒)，基 于电子-自旋交换相互作用的BAP机理在自旋弛豫过程中起着主导作用. 关键词： 光物理 自旋极化 双光子光电子发射 砷化镓     

New carbacylamidophosphates (CAPh) and CAPh-containing coordination compounds: structural peculiarities

Structural Chemistry - The new carbacylamidophosphate derivative HL1 (1) with general formula Cl3CC(O)N(H)P(O)(CH2C5H4N)2 named...     

Radical carbonylation with [11C]carbon monoxide promoted by oxygen-centered radicals: experimental and DFT studies of the mechanism

Photoinitiated carbonylation of alkyl iodides with [11C]carbon monoxide (11C t1/2=20.4 min) is enhanced by ketones that have lowest-lying excited triplet state of npi* character. For example, adding 5 mol % of acetophenone increases radiochemical yields from 3 to 59% in brief 6-min long reactions. Similar or higher yields were achieved by adding di-tert-butyl peroxide. Since radicaloid npi* exited-state ketones and tert-butoxyl radicals have similar reactivity, the photosensitization proceeds most likely via a H-atom transfer mechanism rather than via energy transfer. We propose a mechanism that can account for the enhancement as well as for the formation of observed byproducts. The energy profile obtained by DFT calculations support the feasibility of the mechanism, and observed experimental differences in reactivity could be well rationalized by the calculated data. NBO calculations were performed to further analyze the obtained energetics. Various [carbonyl-11C]esters and some [carbonyl-11C]amides were synthesized in good radiochemical yields from primary and secondary alkyl iodides illustrating the utility of dialkyl peroxides to accelerate the carbonylations. These findings have potential in elaborating new synthetic protocols for the production of 11C-labeled tracers for positron emission tomography.     

Approach to 5-substituted 6,7,8,9-tetrahydro-5H-pyrido[3,2-c]azepines

An approach to 5-substituted 6,7,8,9-tetrahydro-5H-pyrido[3,2-c]azepines via the cyclization of 1-(2-(3-azidopropyl)pyridin-3-yl)alkanones under Staudinger–aza-Wittig reaction conditions is described. The overall reaction sequence includes eight steps and allows for the preparation of gram quantities of the title products. In some cases, the formation of 5,7,8,9-tetrahydrooxepino[4,3-b]pyridine derivatives was observed.     

Reaction of N≡W(O(t)Bu)3 with σ3λ5-phosphoranes. The [2 + 2] cycloaddition across the W≡N triple bond results in the first representative of an inorganic four-membered metallacycle with conjugated endo- and exocyclic double bonds

The reactions of N≡W(O(t)Bu)(3) with the low-coordinate phosphorus compounds (Me(3)Si)(2)NP(NSiMe(3))(2) (I) and (Me(3)Si)(2)NPS(N(t)Bu) (II) were studied. Quantum chemical calculations were used to determine why Mo- and W-containing compounds with the same composition have different molecular structures.     

Focused enumeration and assessing the structural diversity of scaffold libraries: conformationally restricted bicyclic secondary diamines

Comprehensive enumeration of conformationally restricted bicyclic secondary diamines (CRDA) was performed within defined structural limits, yielding a library of all theoretically possible compounds of this class, potentially useful as building blocks for drug design. In order to assess structural diversity of the generated library, molecular geometries of the library members were optimized using DFT calculations. It was shown that the distance between the amino groups and their relative orientation in space vary widely over the whole library, which might be beneficial for diversity-oriented conformational restriction approach in drug discovery. There are many representatives of "three-dimensional" scaffolds in the CRDA library. Selected literature data on biological activity of the known CRDA derivatives were discussed, demonstrating utility of the CRDA scaffold hopping in drug design.     

Evanescent quadrupole polariton

In this work we demonstrate the formation of a new type of polariton on the interface between a cuprous oxide slab and a polystyrene microsphere placed on the slab. The evanescent field of the resonant whispering gallery mode (WGM) of the microsphere has a substantial gradient, and therefore effectively couples with the quadrupole 1S excitons in cuprous oxide. This evanescent polariton has a long lifetime, which is determined only by its excitonic and WGM component. The polariton lower branch has a well-pronounced minimum. This suggests that this excitation is localized and can be utilized for possible BEC. The spatial coherence of the polariton can be improved by assembling the microspheres into a linear chain.