负载型BINAP-M类催化剂

1,1'-联萘-2,2'-双二苯膦与金属配位化合物(BINAP-M)作为最重要和著名的手性催化剂之一,过去的几十年中在工业和基础理论研究中受到广泛关注。虽然BINAP-M作为均相手性催化剂具有活性高和选择性好的特点,但存在价格昂贵、应用成本较高和难以回收利用等局限性,特别是催化剂残留在合成产物中,如药品中,限制了其在工业上的大规模应用。因此,寻求既能保持高催化活性,又能方便回收和循环应用的BINAP-M类催化剂成为重要研究课题。本文总结了近年来可回收BINAP-M催化剂研究进展,重点介绍了吸附负载型与共价负载型BINAP-M催化剂在可回收领域的研究成果,分析讨论了不同类型可回收的负载型BINAP-M催化剂的优缺点。在此基础上,本文还介绍了一种具有“柔性桥链”结构的共价负载BINAP-M催化剂,并分析了其在“拟均相”催化反应中的应用前景,为负载型催化剂的设计与制备提供了新的研究思路。     

气相色谱/质谱-选择离子检测法同时测定大米中的25种持久性有机污染物

利用超声波提取、固相萃取净化对样品进行前处理,然后采用气相色谱/质谱-选择离子检测模式对大米中的25种持久性有机污染物进行了分析。色谱条件:DB-35MS毛细管色谱柱(30 m×0.25 mm i.d.×0.25 μm);载气为氦气,流速1 mL/min;进样口温度300 ℃;不分流进样,进样量1 μL;柱温为程序升温模式。质谱条件:电子轰击电离源,70 eV;采集方式为选择离子方式,扫描质量范围50~450 u。实验采用保留时间以及定性、定量特征离子的丰度比定性,采用峰面积外标法定量,制作了25种持久性有机污染物的标准工作曲线。不同浓度水平的添加回收率试验表明,25种持久性有机污染物的添加回收率为81.99%～100.60%,相对标准偏差为2.37%～18.48%,除异狄氏剂、反式氯丹和顺式氯丹的检测限分别为20,30和20 ng/g外,其他有机污染物的检测限为0.1～5 ng/g。该方法的灵敏度、准确度和精密度均符合农药多残留测定技术的要求。     

分析保护剂补偿基质效应-气相色谱-质谱法快速测定水果中40种农药残留

建立了水果中40种农药化合物的气相色谱-质谱(GC-MS)多残留检测方法,评价了添加分析保护剂对农药残留分析的补偿基质效应和对定量结果可靠性的影响。采用可以溶于丙酮有机溶剂的聚乙二醇Polyethylene Glycol 400(PEG 400)和橄榄油作为保护剂组合进行定量分析。水果样品采用乙腈提取,微型固相萃取小柱净化,大体积进样,GC-MS选择离子监测(SIM)模式检测。40种农药化合物在1～200 μg/L范围内线性关系良好,线性相关系数在0.99以上,检出限(以信噪比为3计)为0.1～3.0 μg/L。除乐果外,其他化合物的添加回收率为75%～119%,相对标准偏差均小于16.6%。通过对添加分析保护剂的校准曲线与基质匹配校准曲线的定量准确性的比较,发现加入分析保护剂方法可以代替基质匹配校正方法,同时采用大体积进样和微型固相萃取净化相结合的方法,大大减少了样品前处理量。将所建立的分析保护剂方法用于苹果、桃子、橙子、香蕉和葡萄等水果样品的分析,基质补偿效应良好,有效地克服了水溶性分析保护剂对气相色谱分析有影响的缺点。     

A dinuclear palladium catalyst for α-hydroxylation of carbonyls with O2

A chemo- and regioselective α-hydroxylation reaction of carbonyl compounds with molecular oxygen as oxidant is reported. The hydroxylation reaction is catalyzed by a dinuclear Pd(II) complex, which functions as an oxygen transfer catalyst, reminiscent of an oxygenase. The development of this oxidation reaction was inspired by discovery and mechanism evaluation of previously unknown Pd(III)-Pd(III) complexes.     

The pointwise estimate of solutions to the parabolic conservation law in multi-dimensions

In this paper we consider the parabolic conservation law with large initial data which has a big perturbation. Using the method of Green function, we first obtain the decay rates of the derivatives of the solutions in L ² and L ^∞ spaces, and then the pointwise estimate of the solutions.     

Large-time behavior for the solution to the generalized Benjamin–Bona–Mahony–Burgers equation with large initial data in the whole-space

In this paper, we consider the global existence as well as the optimal decay estimates of the Cauchy problem for the multi-dimensional Benjamin–Bona–Mahony–Burgers equation with large initial data in the whole-space. And these results are obtained by Green?s function method, Fourier analysis method, energy estimates method combined with the time-frequency decomposition method.     

An efficient synthesis of 3-arylmethyl-7,8-dihydro-6H-chromene-2,5-diones from Baylis–Hillman adduct acetates under solvent-free conditions

A simple, efficient synthesis of 3-arylmethyl-7,8-dihydro-6H-chromene-2,5-dione 4 from Baylis–Hillman adduct acetates derived from aromatic aldehydes and cyclohexane-1,3-diones under solvent-free conditions is described. Interestingly, when Baylis–Hillman adducts derived from aliphatic aldehydes were tested under the similar conditions, the unexpected stereoisomers 5 and 6 were obtained in moderate yields. A plausible mechanism for the formation of 4–6 is proposed.