丁二酸酐与SnCl2·2H2O共催化含水乳酸缩聚制备高分子量聚乳酸

用丁二酸酐与SnCl2.2H2O共催化含水乳酸本体缩聚,合成黏均分子量为6×104的聚乳酸.合成反应时间短,聚乳酸产率高、纯度好.单体为含水10%～15%的乳酸.聚合方法环境友好,不使用任何共沸溶剂.讨论了催化剂用量、反应温度、聚合时间等对聚合反应的影响,并用红外光谱和核磁共振光谱对合成的聚乳酸进行了表征.     

几种金属盐催化剂对苯甲醛肟重排生成苯甲酰胺的催化作用

考察了SnCl2,CdCl2,Cr(CH3COO)3,Cr(NO3)3四种金属盐对苯甲醛肟重排生成苯甲酰胺反应的催化作用;以SnCl2作为模型催化剂,探讨了催化剂用量、反应温度及反应时间等因素对产率的影响,确定了最佳反应条件.结果表明,SnCl2对苯甲醛肟重排生成苯甲酰胺反应的催化效率最高;最佳反应条件为:n(SnCl2)∶n(苯甲醛肟)=2∶5,反应温度110℃,反应时间19h,相应的苯甲酰胺产率达57.6%.     

Ni/C催化剂上山梨醇氢解反应中碱对乳酸形成的影响

山梨醇是重要的生物基平台化合物,其选择加氢裂解制备乙二醇和1,2-丙二醇等低碳二元醇,是一个具有重要科学意义和应用前景的催化过程.山梨醇氢解反应涉及C-C键和C-O键等化学键的裂解,裂解选择性尤为关键.通常情况下,添加NaOH,KOH,Ca(OH)2,CaO和Ba(OH)2等碱性物质可增加糖醇转化率和二元醇选择性,但也会生成大量乳酸等副产物.研究乳酸的生成途径,探索抑制乳酸生成的方法,对于提高山梨醇加氢裂解制备低碳二元醇的选择性具有重要意义.本文以Ni/C催化剂上山梨醇加氢裂解反应为模型反应,研究了碱性化合物添加剂类型及其用量对乳酸生成的影响.根据加氢裂解机理分析可知,糖醇氢解主要涉及以下关键步骤:在碱的存在下,多元醇在金属催化剂上发生脱氢反应生成相应的羰基中间体;然后,羰基中间体在碱性介质中通过逆羟醛缩合反应,发生C-C键断裂.因此,在糖醇氢解反应和C-C键断裂中,添加碱性化合物将会不可避免地生成乳酸.结果表明,以NaOH和Ca(OH)2为添加剂时,山梨醇加氢裂解生成乳酸的选择性分别为15.1％和8.9％.而以La(OH)3为添加剂时,生成乳酸的选择性仅为0.1％.以Ca(OH)2和La(OH)3为添加剂时反应具有高活性,山梨醇转化率均可达到99％以上.分别以Ca(OH)2和La(OH)3为添加剂,研究了碱性添加剂用量对山梨醇氢解反应的影响.结果表明,以Ca(OH)2为添加剂时,山梨醇转化率和乳酸选择性均随着Ca(OH)2用量增加而增加;当OH-投料量为11.06 mmol时,乳酸选择性可达11.7％.而以La(OH)3为添加剂时,即使La(OH)3用量仅为0.08 mmol时,山梨醇转化率也可高达99％;继续增加La(OH)3用量,对乳酸的选择性影响不大;当OH-投料量为11.06 mmol时,乳酸选择性也只有0.3％.对山梨醇加氢裂解反应分析可知,与Ca(OH)2相比,La(OH)3添加剂可使C2和C4产物的总选择性从20.0％增加到24.5％.上述结果表明La(OH)3可高效促进山梨醇加氢转化.为了探索Ca(OH)2或La(OH)3为添加剂时山梨醇加氢裂解产物分布不同的本质原因,以Ni/C催化剂催化的丙酮醛加氢转化为探针反应,探讨了乳酸形成的可能路径.结果表明,丙酮醛可能是山梨醇氢解反应的关键中间体之一.在仅以Ni/C催化加氢时,丙酮醛容易被转化为1,2-丙二醇;当只存在碱性添加剂时,丙酮醛可发生重排并被转化为乳酸主产物,这可能是乳酸生成的主要原因.进一步研究表明,以Ca(OH)2为添加剂时,乳酸选择性是以La(OH)3为添加剂时的1.9倍.在Ni/C催化剂和碱性添加剂共存时,由于碱性添加剂的区别,则会得到不同选择性的1,2-丙二醇和乳酸.结果表明,通过丙酮醛催化加氢可得到1,2-丙二醇,也可以通过重排反应生成乳酸;这两类反应是竞争性的.在山梨醇氢解反应中,以Ca(OH)2为添加剂时,加氢反应和重排反应均可发生.而以La(OH)3为添加剂时,丙酮醛加氢反应占主导,仅生成微量乳酸.该研究对提高山梨醇催化加氢裂解选择性具有参考意义.     

Ni/C催化剂上山梨醇氢解反应中碱对乳酸形成的影响（英文）

山梨醇是重要的生物基平台化合物,其选择加氢裂解制备乙二醇和1,2-丙二醇等低碳二元醇,是一个具有重要科学意义和应用前景的催化过程.山梨醇氢解反应涉及C-C键和C-O键等化学键的裂解,裂解选择性尤为关键.通常情况下,添加NaOH,KOH,Ca(OH)_2,CaO和Ba(OH)_2等碱性物质可增加糖醇转化率和二元醇选择性,但也会生成大量乳酸等副产物.研究乳酸的生成途径,探索抑制乳酸生成的方法,对于提高山梨醇加氢裂解制备低碳二元醇的选择性具有重要意义.本文以Ni/C催化剂上山梨醇加氢裂解反应为模型反应,研究了碱性化合物添加剂类型及其用量对乳酸生成的影响.根据加氢裂解机理分析可知,糖醇氢解主要涉及以下关键步骤:在碱的存在下,多元醇在金属催化剂上发生脱氢反应生成相应的羰基中间体;然后,羰基中间体在碱性介质中通过逆羟醛缩合反应,发生C-C键断裂.因此,在糖醇氢解反应和C-C键断裂中,添加碱性化合物将会不可避免地生成乳酸.结果表明,以NaOH和Ca(OH)_2为添加剂时,山梨醇加氢裂解生成乳酸的选择性分别为15.1%和8.9%.而以La(OH)_3为添加剂时,生成乳酸的选择性仅为0.1%.以Ca(OH)_2和La(OH)_3为添加剂时反应具有高活性,山梨醇转化率均可达到99%以上.分别以Ca(OH)_2和La(OH)_3为添加剂,研究了碱性添加剂用量对山梨醇氢解反应的影响.结果表明,以Ca(OH)_2为添加剂时,山梨醇转化率和乳酸选择性均随着Ca(OH)_2用量增加而增加;当OH~-投料量为11.06 mmol时,乳酸选择性可达11.7%.而以La(OH)_3为添加剂时,即使La(OH)_3用量仅为0.08 mmol时,山梨醇转化率也可高达99%;继续增加La(OH)_3用量,对乳酸的选择性影响不大;当OH~-投料量为11.06 mmol时,乳酸选择性也只有0.3%.对山梨醇加氢裂解反应分析可知,与Ca(OH)_2相比,La(OH)_3添加剂可使C2和C4产物的总选择性从20.0%增加到24.5%.上述结果表明La(OH)_3可高效促进山梨醇加氢转化.为了探索Ca(OH)_2或La(OH)_3为添加剂时山梨醇加氢裂解产物分布不同的本质原因,以Ni/C催化剂催化的丙酮醛加氢转化为探针反应,探讨了乳酸形成的可能路径.结果表明,丙酮醛可能是山梨醇氢解反应的关键中间体之一.在仅以Ni/C催化加氢时,丙酮醛容易被转化为1,2-丙二醇;当只存在碱性添加剂时,丙酮醛可发生重排并被转化为乳酸主产物,这可能是乳酸生成的主要原因.进一步研究表明,以Ca(OH)_2为添加剂时,乳酸选择性是以La(OH)_3为添加剂时的1.9倍.在Ni/C催化剂和碱性添加剂共存时,由于碱性添加剂的区别,则会得到不同选择性的1,2-丙二醇和乳酸.结果表明,通过丙酮醛催化加氢可得到1,2-丙二醇,也可以通过重排反应生成乳酸;这两类反应是竞争性的.在山梨醇氢解反应中,以Ca(OH)_2为添加剂时,加氢反应和重排反应均可发生,而以La(OH)_3为添加剂时,丙酮醛加氢反应占主导,仅生成微量乳酸.该研究对提高山梨醇催化加氢裂解选择性具有参考意义.     

聚合离子液体在催化转化果糖制备乳酸中的应用

化学法分解糖类制备乳酸大都需要苛刻的反应条件,如高浓度强碱、较高的反应温度等.介绍了一种以聚合离子液体([IMEP]Cl)为催化剂,采用水热法直接催化转化果糖制备乳酸的方法,并对聚合离子液体类型、碱类型、反应温度、[IMEP]Cl与Na OH相对量以及底物浓度等实验条件进行了优化.结果表明,在100℃条件下,底物浓度为25mmol/L时,反应30 min乳酸达到最高收率65%,[IMEP]Cl与Na OH浓度分别为100和50 mmol/L.该方法有效降低了水热法合成乳酸的反应温度和碱浓度,并且[IMEP]Cl经过5次循环利用仍有较好的催化效果,乳酸收率仍保持在55%以上.对该体系催化转化果糖制备乳酸的反应机理进行了初步的推测.表明以聚合离子液体为催化剂催化转化碳水化合物制备乳酸有着较好的前景.     

SnCl4·5H2 O/C催化合成谷氨酸月桂酯

以谷氨酸和月桂醇为原料,固体酸SnCl4·H2O/C为催化剂合成了谷氨酸月桂酯.正交实验得出最佳的反应条件为月桂醇100 mmol, n(谷氨酸) ∶ n(月桂醇)＝1 ∶ 1, SnCl4·H2O/C 1.2 g, 135 ℃反应4.0 h,醇转化率97.9%.     

活性炭担载的铂催化剂在碱性条件下选择性氧化甘油制备乳酸（英文）

生物柴油是一种环境友好的燃料,随着其生产及应用的快速增长,其生产过程中重要的副产物甘油将会大量过剩.因此,将甘油转化为高附加值的化学品对于提高生物柴油整体竞争力具有重大意义.乳酸是重要的化工原料,可用于制备生物兼容和可降解的聚乳酸塑料,广泛应用于食品和医药等领域.近年来,由甘油制乳酸的研究受到格外关注,相对于水热反应和氢解反应等,催化选择氧化反应因温和的反应条件而更具竞争力.目前,甘油催化选择氧化制乳酸一般需加入较高比例的NaOH,而碱的类型对反应性能的影响鲜有报道.另外,催化剂常采用TiO_2和CeO_2等氧化物载体,而炭载体具有比表面积较大、在酸碱溶液中稳定及贵金属易于回收等优点,在催化领域有着广泛应用.因此,本文研究了活性炭(AC)担载的Pt催化剂在甘油催化选择氧化制乳酸反应中的催化性能.首先研究了Pt/AC催化剂和碱在甘油催化选择氧化制乳酸过程中的催化作用.实验发现,Pt/AC和碱协同作用才能得到乳酸.Pt/AC催化剂在甘油脱氢生成中间产物(甘油醛和二羟基丙酮)的过程中起主导作用,碱的存在能够促进甘油羟基脱氢;中间产物实验证实,中间产物生成乳酸过程中碱起主导作用,它促进甘油醛和二羟基丙酮脱水反应和坎尼扎罗重排反应获得乳酸.进一步研究发现,中间产物二羟基丙酮比甘油醛更有利于乳酸生成,而Pt/AC催化剂有利于中间产物氧化为甘油酸.进一步研究了不同类型的碱对反应性能的影响.结果表明,碱金属氢氧化物(LiOH,NaOH,KOH)比碱土金属氢氧化物(Ba(OH)_2)更有利于提高甘油转化率和乳酸选择性.在加入碱金属氢氧化物条件下,甘油转化率与其离子半径呈正相关,而乳酸选择性则呈相反趋势.在LiOH存在下,乳酸选择性明显高于NaOH和KOH条件.当LiOH:甘油摩尔比为1.5时,甘油转化率和乳酸选择性均最高.在较低的LiOH与甘油摩尔比时,随着反应的消耗,溶液中的OH–减少,其促进甘油脱氢的作用变弱,并且不利于中间产物进行坎尼扎罗反应,故反应活性和乳酸选择性较差;而当LiOH比例过高时,会导致溶解氧浓度迅速降低,从而使甘油转化率和乳酸选择性下降,同时副产物甘油酸的选择性有所提高.这可能是因为较高比例的碱会促进中间产物甘油醛生成,该中间产物在Pt/AC催化作用下发生进一步氧化反应生成甘油酸.研究了反应时间对催化性能的影响.结果表明,反应6 h后,甘油已经完全转化,乳酸选择性最高,达到69.3%;进一步延长反应时间,乳酸选择性有所下降,而副产物乙酸选择性略有增加,这可能是部分乳酸分解所致.Pt/AC催化剂经5次循环使用后仍保持了较高的甘油转化率和乳酸选择性     

嗜热古细菌Sulfolobus tokodaii脱卤酶在D-乳酸生产中的应用

将来源于嗜热古菌Sulfolobus tokodaii的脱卤酶(L-HADST)基因克隆到载体p ET28b,转化大肠杆菌BL21(DE3)进行表达,在蛋白的N末端带有6个组氨酸融合标签,纯化后经聚丙烯酰胺凝胶电泳显示融合蛋白的分子量约为25000.融合蛋白催化2-氯丙酸(2-CPA)的最适反应温度为70℃,最适p H值为9.5.以外消旋2-CPA为底物生产D-乳酸,利用HPLC检测反应液中2-CPA及乳酸的变化,发现L-HADST只催化L-2-CPA脱氯反应.对酶催化反应条件进行了优化,结果表明,在p H值为9.5,温度为60℃的条件下,当反应体系中缓冲液浓度为3 mol/L,底物浓度为0.5 mol/L,酶浓度为3×104U/L时有较高的底物转化率及乳酸生成量.依据条件优化结果可知,影响反应速度的因素有底物浓度、缓冲液浓度以及酶浓度,其中底物浓度变化对转换率的影响最明显.     

活性炭担载的铂催化剂在碱性条件下选择性氧化甘油制备乳酸

生物柴油是一种环境友好的燃料,随着其生产及应用的快速增长,其生产过程中重要的副产物甘油将会大量过剩.因此,将甘油转化为高附加值的化学品对于提高生物柴油整体竞争力具有重大意义.乳酸是重要的化工原料,可用于制备生物兼容和可降解的聚乳酸塑料,广泛应用于食品和医药等领域.近年来,由甘油制乳酸的研究受到格外关注,相对于水热反应和氢解反应等,催化选择氧化反应因温和的反应条件而更具竞争力.
　　目前,甘油催化选择氧化制乳酸一般需加入较高比例的NaOH,而碱的类型对反应性能的影响鲜有报道.另外,催化剂常采用TiO2和CeO2等氧化物载体,而炭载体具有比表面积较大、在酸碱溶液中稳定及贵金属易于回收等优点,在催化领域有着广泛应用.因此,本文研究了活性炭(AC)担载的Pt催化剂在甘油催化选择氧化制乳酸反应中的催化性能.
　　首先研究了Pt/AC催化剂和碱在甘油催化选择氧化制乳酸过程中的催化作用.实验发现, Pt/AC和碱协同作用才能得到乳酸. Pt/AC催化剂在甘油脱氢生成中间产物(甘油醛和二羟基丙酮)的过程中起主导作用,碱的存在能够促进甘油羟基脱氢;中间产物实验证实,中间产物生成乳酸过程中碱起主导作用,它促进甘油醛和二羟基丙酮脱水反应和坎尼扎罗重排反应获得乳酸.进一步研究发现,中间产物二羟基丙酮比甘油醛更有利于乳酸生成,而Pt/AC催化剂有利于中间产物氧化为甘油酸.
　　进一步研究了不同类型的碱对反应性能的影响.结果表明,碱金属氢氧化物(LiOH, NaOH, KOH)比碱土金属氢氧化物(Ba(OH)2)更有利于提高甘油转化率和乳酸选择性.在加入碱金属氢氧化物条件下,甘油转化率与其离子半径呈正相关,而乳酸选择性则呈相反趋势.在LiOH存在下,乳酸选择性明显高于NaOH和KOH条件.当LiOH：甘油摩尔比为1.5时,甘油转化率和乳酸选择性均最高.在较低的LiOH与甘油摩尔比时,随着反应的消耗,溶液中的OH–减少,其促进甘油脱氢的作用变弱,并且不利于中间产物进行坎尼扎罗反应,故反应活性和乳酸选择性较差;而当LiOH比例过高时,会导致溶解氧浓度迅速降低,从而使甘油转化率和乳酸选择性下降,同时副产物甘油酸的选择性有所提高.这可能是因为较高比例的碱会促进中间产物甘油醛生成,该中间产物在Pt/AC催化作用下发生进一步氧化反应生成甘油酸.
　　研究了反应时间对催化性能的影响.结果表明,反应6 h后,甘油已经完全转化,乳酸选择性最高,达到69.3%;进一步延长反应时间,乳酸选择性有所下降,而副产物乙酸选择性略有增加,这可能是部分乳酸分解所致. Pt/AC催化剂经5次循环使用后仍保持了较高的甘油转化率和乳酸选择性.     

改性羟基磷灰石催化尿素醇解合成碳酸丙烯酯

 采用浸渍法制备了金属改性羟基磷灰石 (M/HAP) 催化剂, 并考察了其催化尿素醇解合成碳酸丙烯酯的反应性能. 结果表明, 用碱金属、碱土金属和稀土金属改性的 HAP 催化剂活性比 HAP 和相应金属氧化物都有不同程度的提高, 其中 La/HAP 活性最高, 碳酸丙烯酯收率达 91.5%. X 射线衍射、扫描电镜、N2 吸附-脱附和 CO2 程序升温脱附等表征结果表明, 经 La 改性后, 在 La/HAP 表面形成了大量新的强碱性活性位, 这是该催化剂活性高的主要原因.     

Flow-Injection Study and Analytical Applications of the Reactions of Palladium(II) and Platinum(IV) with Tin(II) Chloride in Hydrochloric Acid Solutions

The interaction of palladium(II) and platinum(II) with tin(II) chloride in hydrochloric acid solutions was studied by flow-injection (FI) spectrophotometry. It was found using kinetic measurements in the stopped flow mode that the composition of detected products and the rate of their formation depend on the concentrations of tin(II) and chloride ions in the reaction zone and on the acidity of the solution. Optimal FI conditions were found, and the selectivity of interaction of palladium(II) with tin(II) chloride was estimated for the detection of the signal at 407 nm (yellow form) and 646 nm (green form). It was demonstrated that the reaction of the formation of yellow platinum(IV) complexes is slower than that for palladium(II), especially at rather low concentrations of hydrochloric acid in the reaction flow. Based on the detection of green complexes of palladium(II) with tin(II) chloride, a flow injection method was proposed for the selective spectrophotometric determination of palladium(II) in the presence of other platinum-group metals. The height of the recorded peak is directly proportional to the concentration of palladium(II) in the injected solution in the range of 0.028–0.300 mM. The method was used for the analysis of pharmaceuticals and industrial catalysts.     

Hydrogen production by steam reforming of glycerol over Ni/Ce/Cu hydroxyapatite-supported catalysts

Hydroxyapatite-supported Ni-Ce-Cu catalysts were synthesised and tested to study their potential for use in the steam reforming of glycerol to produce hydrogen. The catalysts were prepared by the deposition-precipitation method with variable nickel, cerium, and copper loadings. The performance of the catalysts was evaluated in terms of hydrogen yield at 600°C in a tubular fixed-bed microreactor. All catalysts were characterised by the BET surface area, XRD, TPR, TEM, and FE-SEM techniques. The reaction time was 240 min in a fixed-bed reactor at 600°C and atmospheric pressure with a water-to-glycerol feed molar ratio of 8: 1. It was found that the Ni-Ce-Cu (3 mass %-7.5 mass %-7.5 mass %) hydroxyapatite-supported catalyst afforded the highest hydrogen yield (57.5 %), with a glycerol conversion rate of 97.3 %. The results indicate that Ni/Ce/Cu/hydroxyapatite has great potential as a catalyst for hydrogen production by steam reforming of glycerol.     

Production of methyltin compounds related to possible conditions in the environment

The methylation of heavy-metal compounds (e.g. mercury, lead, tin) in the environment has great significance owing to the much higher toxicity of their methyl derivatives in comparison with inorganic metal species. In this paper abiological methylation of inorganic tin is described. Ethanol, acetic acid and propionic acid abiologically methylated inorganic tin, and the highest yield of methyltin was observed in the reaction between inorganic tin(II) and ethanol. Furthermore, environmental factors for the methylation, such as pH, temperature, added ethanol, concentration of sodium chloride and photoirradiation, were investigated in this reaction. Methyltin production increased at low pH, and decreased at higher concentrations of sodium chloride. Photoirradiation accelerated the reaction rate, and a shorter wavelength showed a higher rate. Inorganic tin(II) was converted rapidly into monomethyltin, and gradually transformed into dimethyltin and trimethyltin with the course time.     

Preparation of lithium stannide mixtures in organic solvents. A alternate source of lithium in organolithium chemistry

Lithium stannides were prepared from lithium naphthalenide and tin (II) chloride or tin (0) powder in THF solvent at room temperature under dry argon atmosphere. They were characterized with elemental analysis, XRD, and solid ^6,7Li NMR. Stabilities and reactivities of lithium stannides prepared from different conditions were tested and showed they were stable for a limited time at low temperatures. Best reactivity was obtained when they were prepared from tin (II) chloride and an excess of lithium naphthalenide. The lithium stannide mixture can reductively cleave carbon-halogen bonds and yield pinacol coupling with aldehydes. Organolithium compounds prepared from lithium stannides and organic halides add to ketones or aldehydes under Barbier conditions.     

Methylation of tin(II) by methyl iodide in porewater

The methylation of tin(II) chloride by methyl iodide in porewater and formation of monomethyltin as the only methyltin product are described. A factorial experiment tested the effects of concentrations of tin(II), methyl iodide, and oxygen on monomethyltin yields. The experiments gave 0.18 to 12.8 % yield. Analysis of variance (ANOVA) calculations showed that all three variables were significant at the 95 % level. Comparison of yields in aqueous 23 g kg^?1 sodium chloride solutions to those in porewater and to those containing fulvic acid, salicylic acid, and EDTA showed that only fulvic acid significantly reduced yields. Reasons for this observation are discussed and the findings in the model system are related to methylation of tin compounds in sediments.     

Spectrophotometric determination of platinum in experimental catalysts

Conditions have been established and procedures are described for the colorimetric determination of platinum in experimental catalysts and miscellaneous materials. The methods are based on the measurement of the intensity of colour produced by the reaction of chloroplatinic acid with tin(II) chloride. Interference from metals such as chromium, molybdenum and nickel, which are often also present in catalysts, is overcome by selective extraction of the complex into isoamyl alcohol followed by measurement of the absorbance of the alcohol layer.     

Modification of a Pt surface by spontaneous Sn deposition for electrocatalytic applications

In the present communication we explored a simple dip-coating method for spontaneous (without applying an external current or additional reducing agents) modification of Pt surface by both tin oxy-species and tin metal based on hydrolysis of tin chloride complex and autocatalytic (electroless) deposition of tin for fabrication of the fuel cell catalysts with improved CO tolerance. It consisted of (i) Pt immersion into SnCl₂/HCl solution under open-circuit conditions; (ii) subsequent rinsing of the surface by pure water. The resulting Sn-modified Pt surfaces were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Two types of tin species, namely, tin oxide/hydroxide species and metallic tin were identified at Pt surface. Tin oxide/hydroxide species were assumed to be derived as a result of Sn(II) chloride complex hydrolysis, while tin metal particles were most likely deposited spontaneously on Pt surface due to disproportionation of Sn(II) to Sn(IV) and metallic tin, competing with dissolution of the Sn deposit in strongly acidic medium. Modifying tin species show a satisfactory stability in 0.5-M H₂SO₄ solution at potentials relevant to low-temperature fuel cell operating conditions (below 0.6 V vs. a standard hydrogen electrode, SHE).     

Application of Silica Chemically Modified by Sulfur-Containing Groups to the Separation and Determination of Platinum and Rhenium in Catalysts Based on Aluminum Oxide

Adsorbents based on silica chemically modified by sulfur-containing groups (dithiocarbamate, thiodiazolethiol, mercaptophenyl, and aminobenzothiazole) quantitatively extract (recovery ≥99%) platinum( IV) from solutions ranging from 4 M HCl to pH 6. Under the conditions of the adsorption separation of platinum(IV), rhenium(VII) is not extracted and remains in the solution. The subsequent quantitative (98–99%) adsorption of rhenium(VII) is achieved in the presence of a 1000-fold excess of tin(II) chloride. Adsorption on the surface of adsorbents leads to the formation of platinum(II) complexes with sulfur-containing groups, luminescent at 77 K on irradiation with UV light. The luminescence spectra of surface platinum( II) complexes are located in the region of 550–700 nm. In the adsorption of rhenium(III) in the presence of tin(II) chloride, intensely colored brown complexes of rhenium formed on the surface of adsorbents. Electron paramagnetic resonance showed that, in the surface complexes, rhenium is in the oxidation state 2+. Silicas chemically modified by sulfur-containing groups were used in the development of procedures for the sequential isolation and determination of platinum and rhenium in solutions after the decomposition of aluminum–platinum–rhenium catalysts.     

Synthesis of some new bis-3,4-dihydropyrimidin-2(1H)-ones by using silica-supported tin chloride and titanium tetrachloride

<正>Silica-supported tin chloride and titanium tetrachloride were prepared by the reaction of tin chloride and titanium tetrachloride with activated silica gel in refluxing toluene.These solid acids have been employed as the catalysts for the synthesis of bisdihydropyrimidin -2(1H)-ones from aromatic dialdehydes,1,3-dicarbonyl compounds and urea at 90℃under solvent-free conditions.     

Regio- and diastereocontrol in carbonyl allylation by 1-halobut-2-enes with Tin(II) halides

Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with tin(II) halides are described. Tin(II) bromide in a dichloromethane-water biphasic system is an effective reagent for unusual alpha-regioselective carbonyl allylation of 1-bromobut-2-ene to produce 1-substituted pent-3-en-1-ols. The addition of tetrabutylammonium bromide (TBABr) to the biphasic system produces 1-substituted 2-methylbut-3-en-1-ols via usual gamma-addition which is opposite to the alpha-addition without TBABr. The gamma-addition to aromatic aldehydes exhibits anti-diastereoselectivity, while that to aliphatic aldehydes is not diastereoselective. The allylation of benzaldehyde by 1-chlorobut-2-ene in 1,3-dimethylimidazolidin-2-one (DMI) does not occur with tin(II) chloride or bromide but does proceed with tin(II) iodide and exhibits gamma-syn selectivity which is unusual for a Barbier-type carbonyl allylation. In the carbonyl allylation by 1-chlorobut-2-ene with any tin(II) halide, the addition of tetrabutylammonium iodide (TBAI) accelerates the reaction and enhances gamma-syn selectivity. The use of tin(II) iodide and TBAI produces 2-methyl-1-phenylbut-3-en-1-ol with high yield and high syn-diastereoselectivity. The syn-diastereoselective carbonyl allylation of 1-chlorobut-2-ene using tin(II) iodide, a catalytic amount of TBAI, and NaI in DMI-H(2)O is applied to various aldehydes.