Convergent synthesis of the common FGHI-ring part of ciguatoxins

Convergent synthesis of the common FGHI-ring part (54) of ciguatoxins was achieved via the following key steps: (i) the Nozaki-Hiyama-Kishi reaction connecting the F-ring part (6) with the I-ring part (7); (ii) regio- and stereoselective epoxidation; (iii) the 6-exo-epoxide opening reaction forming simultaneously the H-ring and the quaternary asymmetric center at C30; (iv) inversion of the C29 stereocenter by a two-step oxidation/reduction process, where the successful inversion depended on proper management of the steric environment of the substrate; and (v) final reductive cyclization constructing the G-ring.     

The reductive etherification of carbonyl compounds using polymethylhydrosiloxane activated by molecular iodine

Aldehydes and ketones undergo a smooth reductive etherification by polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding symmetrical ethers in excellent yields. This new reagent system (PMHS/I₂) provides a simple and convenient route for the preparation of symmetrical ethers from carbonyl compounds.     

Gold-catalyzed rearrangement of substituted allyl aryl ethers

Triphenylphosphinegold(I) complexes catalyze the Claisen-type rearrangement of aryl allyl ethers to the corresponding branched and linear products. The product distribution depends on the olefin geometry of the allylic ether. Stereochemical transfer experiments support an ionic mechanism.     

马铃薯变性淀粉用作钻井液降失水剂的研究

为克服羧甲基纤维素 (CMC)类降失水剂的缺陷 ,合成了醚化、接枝热交联淀粉 .将这两种产物单独及复配后用作钻井液降失水剂 ,并依据API标准对其降失水性能进行了评价 ;通过正交实验对其合成工艺进行了优化 ;运用红外光谱对其结构进行了表征 .研究结果表明 :合成醚化淀粉时最合适的用水量为 15mL ;合成接枝淀粉时最合适的单体用量为 4 .5 g ,热交联温度在 35℃时所得产品降失水率最高 ;醚化淀粉与接枝淀粉复配质量比为 1∶1时降失水性能较理想可达到 5 0 % ;醚化、接枝反应确已发生并在分子中引入了相应的官能团 .该产物对环境基本无伤害 ,有望部分或者完全取代CMC类钻井液降失水剂     

Formation of aromatic polyetherketone and trans-etherification of aromatic polyetherketone

High molecular weight aromatic polyetherketone (PEK) was found to react with 4,4′-difluorobenzophenone (DFB) in the presence of potassium carbonate in benzophenone or diphenyl sulfone at 300°C, yielding low molecular weight PEK with fluorophenyl end groups, while neither polyetheretherketone (PEEK) nor poly-thioetheretherketoneketone was found to react under similar conditions. Reaction model experiments showed that 4-fluoroben-zophenone reacts with potassium carbonate at 300°C to yield benzoyldiphenyl ether and that benzoyldiphenyl ether undergoes spontaneous trans-etherification in the presence of potassium carbonate at 300°C. These results indicate that the overall reaction yielding PEK of reduced molecular weight consists essentially of DFB oligomerization followed by trans-etherification between the DFB oligomer and PEK. © 1993 John Wiley & Sons, Inc.     

氯铝酸离子液体介质中醚化反应的研究

 在1－烷基吡啶、1－甲基－3－烷基咪唑季铵盐或盐酸三甲铵与无水AlCl3构成的室温离子液体反应介质中，尝试进行了叔丁醇的醚化反应．结果表明，在中性或碱性氯铝酸离子液体中，叔丁醇与甲醇、乙醇、丙醇、丁醇或戊醇在80～140℃反应6～12h，可以得到较高的醇转化率和醚选择性，而且产物叔丁基醚和离子液体系分层，便于分离．     

丙烯水合醚化反应过程中丙酮生成机理的研究

 在与色－质联用仪相连的微反装置上，考察了Hβ沸石及改性的\r\nHβ沸石催化剂上丙烯水合醚化及异丙醇脱水的反应行为．丙烯水合醚\r\n化反应中有副产物丙酮生成，而异丙醇单独进料时产物中没有发现丙酮\r\n的生成．这表明丙酮并不是异丙醇氧化脱氢的结果，而是一个应予重视\r\n的不利于丙烯水合醚化的副反应．用同位素示踪反应对丙酮的生成机理\r\n进行了探讨，为研制抑制这一副反应的新催化剂提供了参考依据．     

粘胶纤维醚化反应的研究

为制备纤维状离子交换体,研究了粘胶纤维与二氯乙酸(DCA)在碱性介质中的非均相醚化反应。交联型羧乙基粘胶纤维(CCEV纤维)中羧基的形成速率R=k[DCA]～(1.03)[NaOH]～(1.05)(mmol/kgs)。醚化反应的表现活化能在低于66℃时为47.88kJ/mol.高于66℃时为42.73kJ/mol。CCEV纤维具弱酸性阳离子交换特性,含羧基450mmol/kg的CCEV纤维依旧保持纤维形态。