Characterization of Alkane Diol-CD Complexes. Acid Denitrosation of N-Methyl-N-Nitroso-p-Toluenesulphonamide as a Chemical Probe

A study was carried out on the acid denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in mixed systems made up of linear (geminal and terminal) alkyl diols and β-cyclodextrin (CD). The alkyl diols used allowed us to vary the length of the hydrocarbon chain from 2 to 6 carbon atoms. The observed rate constant, k _obs, decreases in the presence of CD. The inhibition profile decreases as the as the number of carbons in the chain is increased. This behaviour can be interpreted as a consequence of a balance between the complexation processes of MNTS and the alkyl diols by the CD. At a constant CD concentration and increase in the diols concentration decreases the concentration of free cyclodextrin available to complex with MNTS molecules and therefore produces an increases in the observed rate constant. The results were interpreted in terms of two different models; trough the presupposition and non-presupposition of a stoichiometry for the CD-diols complex. Both models agreed quite well and allow us to determine the uncomplexed cyclodextrin concentration in each case as well as the stoichiometry of the complexes. The binding constant for both types of alkane diols increase with increasing the number of carbon in the chain. Besides, the binding constant of the α,ω-alkane diols is higher than for the analog α,β-alkane diols. One of the main consequences of this study is that the acid denitrosation of MNTS can be use to obtain the stochiometry of the CD-diol complexes and to monitor the free cyclodextrin concentration.Electronic Supplementary Material Supplementary material is available for this article at     

Synthesis and photoisomerization of dithienylethene-bridged diporphyrins

Dithienylethene-bridged diporphyrins 1-6 were prepared as photochemical switching molecules. Porphyrin and dithienylethene are directly linked in 1, and linked, respectively, through a 1,4-phenylene spacer in 2, through a 4-ethynylphenylene spacer in 3, and through a di-4-phenylethynylene spacer in 4, while meso-ethynylated porphyrin and dithienylethene are directly connected in 5 and linked through a 1,4-phenylene spacer in 6. Compounds 1, 2, and 5 do not undergo any photochemical isomerization, probably due to efficient quenching of the excited dithienylethene by the attached porphyrin moiety via intramolecular energy transfer. Compounds 4 and 6 undergo open-to-closed and closed-to-open photoisomerizations in quantum yields of 4.3 x 10(-)(2) and 1.8 x 10(-)(3), and 2.6 x 10(-)(3) and 7.5 x 10(-)(4), respectively, by irradiation with 313 and 625 nm light, which are considerably smaller than quantum yields of 0.52 and 3.8 x 10(-)(3) for reference dithienylethene molecule 7. The fluorescence of 4 was regulated in a reversible manner by the photoisomerization of the dithienylethene moiety. In addition, the absorption properties of the porphyrin in 6 changed in response to the photochromic reaction of the dithienylethene bridge.     

Aspects of stereochemistry—I Properties and reactions of some diols

The extent of intramolecular hydrogen-bonding, as determined by infra-red spectroscopy in the hydroxyl stretching region, in certain vicinal diols of cyclohexane, cyclopentane, tetrahydropyran and tetrahydrofuran and in related compounds provides evidence for the stabilities of different conformations. In certain compounds these stabilities can be affected by hydrogen bonding from a substituent hydroxyl group to a ring oxygen. Additional evidence is provided in the case of the tetrahydropyran diols by [M]_D values. The rate of reaction of the vicinal diols of these cyclic systems with glycol splitting reagents, and their zone electrophoretic mobility in an alkaline borate buffer is influenced by the presence of a ring oxygen.     

meso-Alkyl-substituted meso-meso linked diporphyrins and meso-alkyl-substituted meso-meso, beta-beta, beta-beta triply linked diporphyrins

[reaction: see text] AgPF6-promoted oxidation of 5,10,15-trialkyl zinc(II) porphyrins led to formation of meso-meso linked diporphyrins, which were further oxidized with Sc(OTf)3 and DDQ to give meso-meso, beta-beta, beta-beta triply linked diporphyrins that exhibited a stronger aggregation propensity than corresponding meso-aryl diporphyrins.     

二醇的单保护反应研究进展

综述了近年来二醇的选择性单保护反应的方法, 包括对称二醇的单醚化反应和单酯化反应, 不对称二醇的选择性单醚化反应和单酯化反应, 手性化合物中二醇的选择性单保护反应, 手性试剂和生物催化剂在二醇的选择性单保护反应中的应用. 另外, 还讨论了二醇的选择性单保护反应在天然产物合成中的应用.     

Sharpless asymmetric dihydroxylation of 5-aryl-2-vinylfurans: application to the synthesis of the spiroketal moiety of papulacandin D

[formula: see text] Using the Sharpless catalytic asymmetric dihydroxylation reaction on 5-aryl-2-vinylfurans, diols are produced in high enantioexcess. The resulting diols can be efficiently transformed into the spiroketal ring precursor of the antifungal compound papulacandin D. Stereoselective reduction of this precursor followed by a diastereoselective dihydroxylation completes the synthesis of a mannopyranoside isomer of a papulacandin derivative.     

Unexpected role of O-2 "protecting" groups of glycosyl donors in mediating regioselective glycosidation

Glycosidation of several vicinal diols reveals that exquisite regioselectivity can be achieved by using 2-O-benzoyl n-pentenyl glycoside donors and/or their cyclic 1,2-ortho ester counterparts. The regioselective preferences for both are the same, although ratios and yields may differ. In stark contrast, glycosidation of the diols with the corresponding 2-O-benzylated donors gives poor, if any, regioselectivity.     

Boronic acids for sensing and other applications - a mini-review of papers published in 2013

Boronic acids are increasingly utilised in diverse areas of research. Including the interactions of boronic acids with diols and strong Lewis bases as fluoride or cyanide anions, which leads to their utility in various sensing applications. The sensing applications can be homogeneous assays or heterogeneous detection. Detection can be at the interface of the sensing material or within the bulk sample. Furthermore, the key interaction of boronic acids with diols allows utilisation in various areas ranging from biological labelling, protein manipulation and modification, separation and the development of therapeutics. All the above uses and applications are covered by this mini-review of papers published during 2013.     

FeBr3/Me6TREN催化MMA反向原子转移自由基聚合研究

对FeBr3/Me6TREN催化的反向原子转移自由基聚合进行了研究.在不同的催化剂、引发剂的配比、聚合温度和配体用量等条件下,该催化体系催化的MMA聚合反应动力学为一级反应,聚合物分子量可控,分子量分布很窄,说明该体系催化的聚合反应为活性可控聚合.通过实验计算了反应的活化能,并利用UV光谱对催化剂进行了研究.     

含不同侧氨基密度的PLGA-(ASP-Diol)x-PLGA共聚物的合成与表征

以N-(苄氧羰基)-L-天冬氨酸和亚硫酰氯反应制备了N-苄氧基天冬氨酸酐,将其与不同链长的二醇(乙二醇、二缩三乙二醇、聚乙二醇200和600)缩聚,合成了含端羟基的天冬氨酸-二醇交替预聚物(ASP-Di-ol)x;以其为大分子引发剂,辛酸亚锡为催化剂进行丙交酯/乙交酯(摩尔比75∶25)开环共聚,合成系列含侧氨基的天冬氨酸-二醇-聚乙丙交酯[PLGA-(ASP-Diol)x-PLGA]多元三嵌段共聚物.用FTIR,1HNMR,EA,DSC和GPC对共聚物结构进行表征.结果表明,影响预聚物分子量的主要因素不是二醇的分子量,而是其端羟基的活性.随着二醇链段长度增加,多元共聚物中氨基含量降低,玻璃化转变温度也明显下降.通过改变二醇链段的长度(或分子量)可有效地控制PLGA-(ASP-Diol)x-PLGA中侧氨基的密度及分布.     

Polyepichlorohydrin diols free of cyclics: Synthesis and characterization

Polymerization of epichlorohydrin (ECH) in the presence of diols, catalyzed by Lewis or protic acids, proceeds by activated monomer mechanism (AMM), i.e., by subsequent additions of protonated monomer molecules to the terminal hydroxyl groups of the growing chain. As opposed to the typical active chain end mechanism, side reactions, including cyclization, are strongly suppressed in the polymerization by AMM and well-defined linear product are obtained. It follows from kinetic considerations, that in order to achieve the high contribution of AMM, the reaction should be carried out at low instantaneous concentration of monomer, and this can be accomplished by slowly adding ECH to the reaction mixture. Using this approach, polyepichlorophydrin diols have been prepared in the M?_n ～ 2500 products with DP _n = [M]₀/[I]₀ can be obtained practically free of cyclic by-products with the yields approaching quantitative. Polyepichlorohydrin diols obtained by AM polymerization are strictly bifunctional, regular head-to-tail polymers containing mainly (≥ 95%) secondary hydroxyl and groups.     

Bifunctional fluorescent probes for hydrogen peroxide and diols based on a 1,8-naphthalimide fluorophore

This report discloses a series of naphthalimide-based bifunctional fluorescent probes for hydrogen peroxide and diols.As a result,these molecules not only demonstrated high turn-on fluorescent response and good selectivity towards hydrogen peroxide over other relevant reactive oxygen species,but also displayed different responses to diols.Therefore,these fluorescent probes could be served as sensitive,selective and practical chemosensors for both hydrogen peroxide and diols under physiologicallike conditions.     

Silenes as novel synthetic reagents: synthesis of diols and lactones from simple alkyldienes

Aryl substituted silenes can be generated by a modified Peterson olefination reaction and trapped in situ to afford silacycles with high diastereoselectivity. These silacycles can be elaborated by ‘Fleming-Tamao’ type oxidation to provide access to functionalized diols and lactones.     

The dynamic covalent chemistry of mono- and bifunctional boroxoaromatics

10-Hydroxy-10,9-boroxophenanthrene reacts rapidly and reversibly with both benzylic and alkane diols in non-polar solvents. The formation of 2:1 adducts between the boroxoaromatic and the diols is favoured. The diol component of the adduct can be exchanged readily and rapidly by treatment of the boroxoaromatic-diol adduct with an alternative diol in solution at room temperature. This reversible covalent chemistry would appear to be ideal for the dynamic assembly of more complex superstructures. However, attempts to extend this dynamic equilibrium to the assembly of macrocycles using the bifunctional boroxoaromatic 5,9-dihydroxy-5,9-dibora-4,10-dioxopyrene failed as a result of changes in the reactivity of the boron centre in the bifunctional boron-containing compound.     

Kinetics and mechanism of the oxidation of some diols by benzyltrimethylammoniumtribromide

The kinetics of oxidation of five vicinal and four non-vicinal diols, and two of their monoethers by benzyltrimethylammonium tribromide (BTMAB) have been studied in 3:7 (v/v) acetic acid-water mixture. The vicinal diols yield the carbonyl compounds arising out of the glycol bond fission while the other diols give the hydroxycarbonyl compounds. The reaction is first-order with respect to BTMAB. Michaelis-Menten type kinetics is observed with respect to diol. Addition of benzyltrimethylammonium chloride does not affect the rate. Tribromide ion is postulated to be the reactive oxidizing species. Oxidation of [1,1,2,2-²H₄] ethanediol shows the absence of a kinetic isotope effect. The reaction exhibits substantial solvent isotope effect. A mechanism involving a glycol-bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidized by a hydride ion transfer to the oxidant, as are the monohydric alcohols.     

Synthesis and properties of waterborne self‐crosslinkable sulfo‐urethane silanol dispersions

A novel type of crosslinkable waterborne polyurethane ionomer was prepared by the acetone process. Two new types of sulfonated diols compatible with this process were synthesized from dimethyl 5‐sodium sulfo isophthalate using a one‐ or two‐stage method. Isocyanate‐terminated polyurethane oligomers were prepared from the sulfonated diols with various combinations of diols and diisocyanates and subsequently reacted with amino silane derivatives. Stable, low‐volatile organic chemical, waterborne dispersions of the sulfo‐urethane silanol polymers spontaneously crosslink upon drying without extra additives or processing steps. Despite the lack of organic coalescing solvents, the dispersions have minimum film‐forming temperatures below 10 °C, regardless of glass‐transition temperature. Tensile strengths up to 6000 psi with elongations between 300 and 600% were obtained for the crosslinked films. The hard‐segment content of the films can be controlled to produce films with a Sward–Rocker hardness value up to 42. Through silane end‐group modification, the crosslinking density of the films can also be modified to produce polyurethanes with a wide range of physical properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3037–3045, 2002     

Unprecedented use of silver(I) N-heterocyclic carbene complexes for the catalytic preparation of 1,2-bis(boronate) esters

Catalytic diboration of internal and terminal alkenes with Ag(I) N-heterocyclic carbene complexes leads to 1,2-bis(boronate) esters as single intermediates, that can be oxidised towards the corresponding diols.     

Polyether-polyester and HMDI Based Polyurethanes:Effect of PLLA Content on Structure and Property

Thermoplastic poly(ether-ester-urethane)s were synthesized from poly(L-lactide) diols (PLLA diols),polytetrahydrofuran diol(PTMG diols),4,4'-dicyclohexylmetlhane diisocyanate (HMDI),and 1,4-butanediol (BDO) by a two-step reaction,and the morphology and property of the resultant TPU could be adjusted by varying the PLLA contents.The soft segment was composed of PLLA and PTMG diols.By controlling the percentage of PLLA in the soft segment,the glass transition temperature and mechanical properties of the polyurethanes could be regulated.Based on the FTIR spectrum,we found that two kinds of hydrogen bonding existed individually in soft matrix and hard domain.The hydrogen bonding in soft matrix was unstable,which could be destroyed during elongation.With in situ stretching WAXS and SAXS experiments,we found that the PLLA crystal was destroyed and the PLLA domain oriented along the stretch direction.Finally,we proposed a schematic model to illustrate the microstructures of these elastomers before and after stretch.     

Synthesis and characterization of liquid crystalline monofunctionalized 'two chain' diols and corresponding low molecular weight siloxane derivatives

The selective synthesis and the thermal behaviour of some cis, cis-(3,5-dihydroxycyclohexyl) 3,4-(alkenyloxy, alkyloxy)benzoates (monofunctionalized 'two chain' diols) are described. Thus, several 3-(alkyloxy)-4-(undecenyloxy)benzoic acids and 4-(decyloxy)-3-(undecenyloxy)benzoic acid have been obtained. The monofunctionalized 'two chain' diols form a hexagonal columnar mesophase through hydrogen bonding. Subsequently, low molecular weight liquid crystalline siloxanes, model compounds for polymers, i.e. two twins and one cyclic product, were synthesized via a hydrosilylation reaction. With respect to the 'two chain' diols, the observed hexagonal columnar mesophase was stabilized and the intercolumnar distance was extended by the siloxane moieties. Remarkably, the thermal behaviour of the cyclosiloxane differs from that of the twins. A cubic mesophase, which can be observed very rarely in thermotropic mesogens, was formed at temperatures below the hexagonal columnar phase.