葡萄糖B-Z体系中酸度变化诱导的复杂振荡反应

本文首次报导了葡萄糖-KBrO₃-丙酮-MnSO₄-H₂SO₄体系的化学振荡反应,在这一体系中改变酸度可产生一系列复杂的振荡现象,当[H₂SO₄]₀>0.36mol·l^-1或[H₂SO₄]₀<0.074mol·l^-1时,体系分别出现二种不同类型的振荡波形OA和OB,OA振荡存在一诱导期,OB振荡无锈导期;OA的振幅较小,但振荡频率比OB快得多;OB的振荡周期逐渐缩短,但OA.却相反变化.当0.074mol·l^-1<[H₂SO₄]₀<0.36mol·l^-1时,体系同时出现上述二种类型的振荡波形,中间存在一过渡区域,即产生连续振荡波形.文章讨论了诱导期及过渡时间与[H₂SO₄]₀的关系,对酸度的影响机理作了说明.     

Synthesis of the new chiral tridentate ligand bis(pyrid-2-ylethyl) menthylphosphine and its use in the palladium-catalyzed allylic alkylations

We describe the synthesis of a new asymmetric P,N,N′-tridentate ligand (bis(pyrid-2-ylethyl) menthylphosphine, BPEMP), containing two pyridyl rings and (1S,2R,5S)-menthylphosphino group. The ligand is obtained in five steps from natural abundant l-menthol. The coordination behavior of the ligand toward cationic (allylic)Pd(II) moiety and its first application in palladium-catalyzed asymmetric allylic alkylation are presented. Crystallographic and spectroscopic analyses reveal that [(η³-allylic)Pd(BPEMP)]⁺ complex forms only one isomer in the solid state as well as in solution.     

Asymmetric Diels-Alder Reactions of Chiral Menthyl α-Sulfinylacrylates

Introducing two chiral auxiliaries, sulfoxide and menthol, into an acrylate would have either matched or mismatched pair systems. The presence of chiral menthol in α-sulfinylacrylates can change the diastereoselectivity from 24% d.e. to a single diastereomer by manipulation of the double asymmetric strategy.     

Particle velocity measurements in induction plasma spraying

Laser Dopple anemometry (LDA) measurements of the particle velocity are carried out during an induction plasma spraying operation. The velocity of nickel alloy particles, or molten droplets, at the exit of an induction plasma torch prior to impact on the substrate is shown to vary with the plasma and powder injection conditions. Plasma spraying under soft vacuum (150–450 Torr) gives rise to substantially higher particle velocities (40–60 m/sec) compared to those attained at atmospheric pressure (10–20 m/sec).     

Remote substituent effect favoring the formation of syn-adducts in the chelation controlled radical reactions of γ-benzyloxy-α-methylenecarboxylic acid esters

The chelation controlled radical reactions of ethyl γ-benzyloxy-α-methylenecarboxylates bearing a bulky γ-substituent, such as CHMe₂, CHPh₂, c-C₆H₁₁ and CH(Ph)OTBDMS, with alkyl iodides gave the syn-adducts with high diastereoselectivities. However, the diastereoselectivity for the substrates bearing a γ-substituent CH(i-Pr)OTBDMS depended critically on the configuration of the substituent; the substrate bearing the OTBDMS group anti to the γ-benzyloxy group showed poor diastereoselectivity, but its diastereomer gave syn-adduct exclusively. The high syn-selectivitiy is referred to the H-atom transfer to the outside face of radical center in the sharply folded seven-membered chelate intermediate bearing the ethoxy group with Z-geometry. The corner flapping of the radical center atom of the global minimum energy conformer generates a local minimum conformer and the H-atom transfer to the outside face of the radical center of the newly formed structure gives the anti-adduct. The poor diastereoselectivity is due to the very small energy difference between the two conformers and consequently both the syn- and anti-adducts are yielded in nearly equal amounts.     

SPECIFIC PROTEIN OCCURRENCE RELATED WITH PHOTOPERIODIC FLOWER INDUCTION IN THE COTYLEDONS OF Pharbitis nil CV. VIOLET

In our experiment, three groups of seedlings of SDP Pharbitis nil cv. violet were sepa-rately treated with three different photoperiods (1,16 h dark period--SD; 2, continuous illumi-nation--CL; 3, 16 h dark treatment with 10 min white light in the middle of the dark period--NB). By analysing proteins in the cotyledons from three groups with 2-D PAGE, we found nodifference in protein pattern between the three groups at 0 or 8 h after photoperiodic treatments.At 24 h after the treatments, a specific protein(MW:19 kD; pI: 4.5)appeared only in the cotyledonsof the seedlings which endured SD. This protein disappeared at 72 h after SD. ActinomycinD could inhibit flowering and the specific protein occurrence when applied to cotyledonsprior to SD, but it had no inhibition effect on flowering as well as the specific proteinoccurrence when applied to cotyledons after SD. Chloroamphenicol, a protein synthesisinhibitor, inhibited flowering when applied to cotyledons prior to or immediately after SD,but it did not i     

Enantioselektive Cyclopropanierung von 1,1-Diphenylethylen und Diazoessigester mit Kupfer-Katalysatoren

Copper(II) compounds catalyze the reaction of 1,1-diphenylethylene with diazoacetic acid ethylester. The main product is 2,2-diphenylcyclopropane carboxylic acid ethylester. The formation of the carbene dimerization products fumaric and maleic acid diethylester can be suppressed by the continuous addition of diazoacetic acid ester to 1,1-diphenylethylene.37 optically active ligands, partly new, were combined with copper(II)-acetate to givein-situ-catalysts. In five cases isolated copper complexes were used as catalysts. The best optical inductions in the formation of 2,2-diphenylcyclopro-pane carboxylic acid ethylester with up to 65.6% ee were achieved withSchiff base ligands, which derive from salicylaldehyde and amino alcohols, obtained from amino acid esters and phenylGrignard.

Prof. Dr.Karl Schlögl, Universität Wien, mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Can the presence of chemically inert species modify the face selectivity in asymmetric induction by cyclodextrins?

Reduction of-cyclodextrin (-CD) aromatic ketone (acetophenone and acetonaphthones) inclusion compounds were carried out in the presence of a large number of chemically inert species as potential co-guests. In several cases, it was observed that stoichiometric molar ratios of these compounds to ketone significantly modify the chiral induction yielding the inverted alcohol enantiomer and increasing the face selectivity. The results were found to depend strongly on the respective structure and shape of both the ketone and the additive, and on the molar ratio of-CD:ketone:third compound. These observations suggest the formation of a three-component inclusion complex in which the geometry of binding of the substrate and its mobility are changed with respect to the binary system.     

Cr_2O_7~(2-)对B-Z振荡反应的影响及其分析应用

研究了Cr2O72-对B-Z化学振荡反应的影响.结果表明,Cr2O27-的加入明显改变该振荡反应的诱导期,且诱导期的改变值Δtin与所加入Cr2O72-的浓度有良好的线性关系,线性范围3.45×10-6~6.20×10-4mol·L-1,相关系数为0.9992,对Cr2O72-扰动B-Z振荡反应的机理进行了探讨.