Asymmetric conjugate addition reactions of Meldrum's acid derived acceptors employing chiral phosphoramidite ligands

[reaction: see text] The enantioselective conjugate addition reaction of Et(2)Zn to Meldrum's acid derived acceptors, mediated by a catalyst formed from Cu(O(2)CCF(3))(2) and a phosphoramidite ligand, is reported. Adducts are obtained in useful yields and up to 94% ee.     

Photoreaction of 2-dicyanomethylene-1,2,3,4-tetrahydro-1,4-methanonaphthalene

Upon irradiation, 2-dicyanomethylenebenzonorbornene f$\text{3}$ was converted into 1-dicyanomethylenebenzobicyclo[3.1.1]heptene $\text{4}$. The reaction pathway is discussed with reference to the photoreaction of parent hydrocarbon.     

Practical synthesis of Dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate

An efficient and reliable procedure for the preparation of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], Rh2(S-PTTL)(4), a universally effective catalyst for a range of enantioselective carbene transformations, is described. The N-phthaloylation of (S)-tert-leucine by the method of Bose with essentially no racemization is a key to this process.     

球壳粒子悬浮系模型化研究——内部相参数对介电谱影响的数值模拟

在Hanai理论基础上对球壳粒子悬浮系的介电模型进行了模拟研究,通过用C++的复数类对理论公式的程序化,建立了介电谱的介电参数与体系内部相参数的关系.所得的解析解可方便地模拟介电弛豫谱依不同相参数的变化曲线,计算并分析了内部参数对介电谱的模式以及介电参数的影响因素.     

Acid-catalyzed transannular cyclization of 3aH-cyclopentene[8]annulene-1,4-(5H,9aH)-diones and some proposed mechanisms

Bicyclic 3aH-cyclopentene[8]annulene-1,4-(5H,9aH)-diones underwent three types of acid-induced transannular reactions, Michael cyclization, [3 + 2] cycloaddition, and Friedel-Crafts ipso-alkylation, depending on the cyclopentenone ring substituent (Me or Ph) and the position of [8]annulenone substituent as well as the nature of acids (BF3, MeSO3H, CF3SO3H). The Me-substituent permitted the Michael reaction for all acids used to give tricyclic diones by the activation of cyclopentenone carbonyl group. However, the Ph-substituent inhibited the Michael reaction for BF3 and MeSO3H but allowed the [3 + 2] cycloaddition and Friedel-Crafts reaction for CF3SO3H depending on the position of annulenone substituent. These CF3SO3H reactions exhibited the following novel rearrangements, affording 2-naphthalenone and 7-acenaphthylene derivatives, respectively. The factors that control the reaction mode of these transannular cyclizations were discussed in view of the constraint twist-boat conformation of [8]annulenone ring as well as the ring substituent effects on the intramolecular cyclization. In addition, these [8]annulenone rings were found to easily undergo the intramolecular [2 + 2] photocyclization to provide the tetracyclic cage compounds which exhibited the facile cycloreversion under the influence of acid.     

Facile synthesis of urea derivatives under mild conditions

Urea derivatives were readily synthesized in good yields under quite mild conditions, i.e., at ambient pressure and room temperature by sulfur-assisted carbonylation of primary amines with carbon monoxide followed by oxidation of the resulting ammonium thiocarbamates with molecular oxygen.     

Synthesis of quinazolines using carbon dioxide (or carbon monoxide with sulfur) under mild conditions

Sulfur‐assisted carbonylation of 2‐aminobenzonitriles with carbon monoxide using K₂CO₃ as a base under ambient conditions (1 atm, 20°C) to afford 2‐hydroxy‐4‐mercaptoquinazolines in excellent yields was found. This carbonylation was applied to chemical fixation of carbon dioxide under mild conditions. Carbon dioxide (1 atm) easily reacted with 2‐aminobenzonitriles at 20°C assisted by 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) to give 2,4‐dihydroxyquinazolines in excellent yields. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:428–433, 2000     

Writing of crystal line patterns in glass by laser irradiation

We examined the laser-induced crystallization to form the fresnoite type Ba₂TiGe₂O₈ crystal line patterns in transition metal ion doped BaO–TiO₂–GeO₂ glass. Ba₂TiGe₂O₈ crystal line was written in 0.6FeO–33.3BaO–16.7TiO₂–50GeO₂ glass by continuous wave yttrium–aluminum–garnet (YAG) laser irradiation. We obtained polarization dependence of Raman spectra in crystal line pattern. Second harmonic generation (SHG) indicated unique fringe patterns from Ba₂TiGe₂O₈ crystal lines.