Sodium Bisulfite: An Efficient Catalyst for Ether Formation via Dehydration of Aromatic/Aliphatic Alcohol

Straightforward etherification of benzyl alcohols ( 1 ) via intermolecular dehydration can be efficiently catalyzed by sodium bisulfite under solvent‐free conditions. In the presence of 0.3 mol% or 0.6 mol% amount of sodium bisulfite, symmetric and unsymmetric ethers are prepared from the corresponding alcohols in high yields (up to 95%). Etherification of benzhydryl alcohols is also discussed.     

Substitution Patterns of Cellulose Ethers - Influence of the Synthetic Pathway

Commercial cellulose ethers are usually prepared under heterogeneous reaction conditions. In contrast, this contribution also describes the derivatization under homogeneous conditions in N-methylmorpholine-N-oxide monohydrate (NMMNO*H₂O) and under heterogeneous conditions after converting native cellulose to amorphous cellulose. Amorphous cellulose is prepared by dissolving cellulose in NMMNO*H₂O followed by precipitation in different media. The degree of order and the porosity of the regenerated cellulose is significantly influenced by the content of water in the precipitating agent. The differences are described by measurements using wide angle X-ray scattering, solid-state ¹³C-NMR, mercury porosimetry, and water/liquid retention values. Three synthetic pathways (heterogeneous, heterogeneous with amorphous cellulose and homogeneous) are compared regarding the structure-property relationship of the cellulose ethers formed. Carboxymethylation, hydroxyethylation, hydroxypropylation and sulfoethylation are considered in detail. The choice of synthetic pathway has a significant influence on the degree of substitution (DS), the distribution of substituents on the level of the anhydroglucose unit (AGU), solubility behavior, and the viscosity of aqueous solutions. In general an increasing solubility and an increasing viscosity are observed from heterogeneous to heterogeneous with amorphous cellulose to homogeneous reaction conditions. There is a remarkable difference between the heterogeneously produced cellulose ethers with a DS distribution C2 ≥ C6 > C3 and the strictly homogeneous etherification in NMMNO*H₂O/organic solvent systems with a DS distribution of C3 > C2 ≫ C6. This high regioselectivity at the secondary OH-groups of the AGU may be caused by the strong solvation behavior of NMMNO*H₂O and thereby a protecting function at the C6-OH-group.     

Synthesis of the methylene bis-tetrahydropyran motif of (−)-exiguolide

A chiral-pool approach for the construction of methylene bis-tetrahydropyran subunit, C₁-C₁₆ fragment, of (−)-exiguolide is described. The synthesis was efficiently accomplished starting from l-glutamic acid and l-aspartic acid involving oxa-Michael reaction and an aldol-driven-reductive etherification as key steps for the formation of tetrahydropyran ring.     

新化合物2,3—亚甲基—5,8—二甲氧基萘的合成、结构及反应的研究

本文报导了一种新化合物2，3－亚甲基－5，8－二甲氧基萘（简称MOCPN）的合成，该化合物与不同类型的醇开环成酸的反应，以及MOCPN和生成的三种醚的质谱，红外光谱，H~1、C~13核磁共振谱数据。光谱数据与预计的化合物结构完全一致。     

二甘醇与乙醇在杂多酸盐催化剂存在下合成二甘醇乙醚

研究了以杂多酸盐为催化剂，由乙醇和二甘醇合成二甘醇乙醚的反应过程。研究表明，磷钨酸银及硅乌酸银具有较高的活性和选择性，其转化率分别为８９．０％和８７．３％，单双醚总选择性分别为７３．４％和８０．６％；磷钼酸银的活性较低。ＩＲ、ＸＲＤ、ＴＧ分析和正丁胺滴定法表面酸度测定表明，杂多酸银盐的催化性能与其所具有的酸性中心有关。     

甘蔗渣／棉短绒混合浆粕制备高粘级CMC的研究

本文研究甘蔗渣/棉短绒混合浆粕制备高粘级羧甲基纤维素(CMC)的溶媒法工艺。实验表明,纤维素的化学成分、微细结构,特别是碱化条件对 CMC 产品取代均一性有很大的影响。当甘蔗渣/棉短绒的配比为30～40/70～60时,碱比为0. 58～0. 63,酸比为0. 65～0. 68,酒比在2. 0～2. 2的范围内可制得取代度0. 73～0. 75,粘度900～1000mPa·s 的 CMC.用化学和 x-射线衍射分析对醚化机理作了初步探讨,本工艺对利用甘蔗渣原料制高粘级CMC 有经济上和实用上的意义。     

化学改性生物柴油制备润滑油基础油

用生物柴油来制备环氧生物柴油,然后在D001树脂的催化作用下,环氧生物柴油和异辛醇进行异构醚化开环反应,合成的改性生物柴油即为润滑油基础油.通过红外光谱对原料和产物的结构进行表征,并对合成的润滑油基础油的性能与环氧生物柴油和150SN矿物润滑油进行了比较.结果表明,所合成的润滑油基础油热稳定性好、黏温性能好、黏度指数大、氧化稳定性良好、承载能力和抗磨性能较好.同时考察了D001树脂重复使用性,发现重复使用5次后仍具有较高催化活性.     

Asymmetric total synthesis of phomonol

An efficient asymmetric total synthesis of phomonol 1 is presented, starting from (S)-1,2-epoxypentane. The synthesis features Sharpless asymmetric dihydroxylation (AD), diastereoselective reductive etherification and Wacker oxidation as key steps.     

End group chemistry of fluoro-oligomers: Highly selective syntheses of diepoxy,diallyl, and tetraol derivatives

Different synthetic methods for the preparation of polyfunctional fluorinated oligomers were explored and the results compared. Fluoropolyether macromonomers bearing epoxy, allyl, and polyhydroxy end groups were synthesized and spectroscopically characterized. For obtaining a polyol (namely tetraol) functionality, a highly selective route was the reaction of the fluoropolyether macrodiol ZDOL with allylic halides and subsequent oxidation reaction at the CC double bond by means of peroxyacids. This approach made it possible to obtain a segmented structure RH-RF-RH in which the molecular body RF consisted of a perfluoropolyether block endcapped by two hydrogenated segments RH, where RH = − CH₂OCH₂CH(OH)CH₂OH. Unlike other more conventional syntheses, which always produce byproducts and higher molecular weight species such as RH-(RF-RH)_n-RF-RH or RH-RF-(RH)_n-, the described method offers high yields and selectivity. The fluoropolyether polyfunctional derivatives offer the possibility to prepare a variety of highly crosslinked fluorinated materials and, owing to their well defined regularly segmented structures, they also constitute interesting models for the understanding of basic structure-property relations of fluoro-oligomers and their copolymers. © 1996 John Wiley & Sons, Inc.