Sulfamic Acid as a Cost-effective Catalyst for Acetolysis of Cyclic Ethers

Sulfamic acid has been used as an efficient catalyst and green alternative for conventional acidic materials to promote the acetolysis reaction of THF to produce 1,4-diacetoxybutane. This method is also applicable in the acetolysis of other cyclic ethers, such as methyl substituted THF and tetrahydropyran and 1,4-dioxane which is less reactivity.     

重氮萘酮在环醚中热解反应研究

三种带有不同取代基的重氮萘酮(la～1c)在THF和二氧六环中加热分解给出不同的产物。1-重氮-4-萘酮(1a)的热解产物主要是重氮萘酮热解后产生的烯酮卡宾(2a)与环醚开环后形成的聚合物;3-甲基-1-重氮-4-萘酮(1b)的热解产物比较复杂,除冠醚类产物之外,还有烯酮卡宾对四氢呋喃和二氧六环的C-H键的插入反应产物、螺环化合物、2-甲基萘酚以及难以分离的聚合物;3-硝基-1-重氮-4-萘酮(1c)的热解产物主要是聚合物,此外还有少量C－H键的插入反应产物和2-硝基萘酚。对重氮萘酮热解反应的机理作了讨论。     

On the number-average molecular weight of poly(1,4-trans isoprene) determined by conventional GPC

We became aware, in the course of our on-going research, that the number-average molecular weight of poly(1,4-trans isoprene) determined by conventional gel permeation chromatography (GPC) in tetrahydrofuran (THF) using polystyrene standards differs from its true value by a factor 2. As far as we know, the Mark-Houwink coefficients of this polymer in a widespread GPC eluent such as THF have never been determined. We provide in this contribution a simple relationship between the number-average molecular weight of poly(1,4-trans isoprene) determined by GPC in THF using polystyrene standards and its true value.     

Enthalpies of dilution and homotactic enthalpic interaction coefficients of THF and 1,4-dioxane at 298.15 k

Enthalpies of dilution at 298.15 K of aqueous solutions of THF and 1,4-dioxane have been determined using flow microcalorimetry. The results obtained were used to determine the homotactic enthalpic interaction coefficients that characterize pair interactions of THF and 1,4-dioxane in aqueous solution. These are briefly discussed from the point of view of intermolecular interaction between the hydrated solute species.     

聚苯乙烯-b-聚氧乙烯-b-聚苯乙烯三嵌段共聚物的自组装

小分子表面活性剂、磷脂、接枝及嵌段共聚物等两亲分子在选择性介质中能够自组装形成特定的分子聚集体 [1,2 ] .嵌段共聚物自组装的某些行为具有生物膜模拟性 ,如最近发现的嵌段共聚物自组装囊泡 [3～ 5] .诸多因素影响着嵌段共聚物在稀溶液中的自组装行为 [6] .对于 ABA型三嵌     

一种碱溶性灰树花菌丝体多糖GFM2A的制备和结构表征

以灰树花菌丝体为原料, 经过碱提取和柱色谱分离纯化, 得到一种碱溶性多糖(GFM2A). 经高碘酸氧化、Smith降解、乙酰解并采用GCMS, IR, 2D NMR等方法对该多糖的化学结构进行了表征. 结果表明, 该多糖由葡萄糖(Glc)、甘露糖(Man)和木糖(Xyl)组成, 其摩尔比为9∶2∶1, 其主链由6个α-1, 3-D-Glc和2个α-1,3-D-Man 构成, 且α-1,3-D-Glc残基O-4位有两个分支, 其中一个分支连接3个β-1,4-D-Glc, 另一个分支连接一个α-1,4-D-Xyl.     

Mechanism of alternating copolymerization of 4-hydroxy-4′-vinylbiphenyl with α-chloromaleic anhydride

The copolymerization of 4-hydroxy-4′-vinylbiphenyl (HVB) with α-chloromaleic anhydride (CMAn) was investigated in THF, 1,4-dioxane, and acetonitrile. The formation of the 1:1 charge transfer complex between HVB and CMAn was confirmed spectroscopically, and the corresponding equilibrium constant (K_eq) was determined as follows: K_eq = 0.19, 0.11, and 0.058 mol/L in THF, 1,4-dioxane, and CH₃CN, respectively. The copolymer composition is affected by the solvent, i.e., the content of HVB in the copolymer obtained in THF or 1,4-dioxane is lower than 50 mol % whereas the copolymer obtained in CH₃CN has excess of HVB units. The maximum rate of copolymerization was observed at a 1:1 initial comonomer mole ratio, irrespective of the solvent polarity. Plots of R_p/[HVB] vs. [HVB] gave a straight line with a slope and an intercept for the copolymerization in THF whereas a straight line in CH₃CN has no slope. On the basis of these results and ¹³C-NMR spectra of the copolymers, the mechanism of the predominant formation of alternating copolymers is discussed.     

The reactions of combined organocuprate-chlorotrimethylsilane reagents with conjugated carbonyl compounds

Organocuprates and chlorotrimethylsilane are compatible as separate species in THF or ether solution at ?50 to ?78°, and in combination can both accelerate and improve 1,4-addition reactions with conjugated carbonyl compounds.     

Extended three-dimensional supramolecular architectures derived from trinuclear (bis-beta-diketonato)copper(II) metallocycles

Neutral trinuclear (triangular) copper(II) complexes of type [Cu3L3] incorporating the 1,4-aryl linked bis-beta-diketonato bridging ligands, 1,1-(1,4-phenylene)-bis(butane-1,3-dione) (H2L2), 1,1-(1,4-phenylene)-bis(pentane-1,3-dione) (H2L3) and 1,1-(1,4-phenylene)-bis(4,4-dimethylpentane-1,3-dione) (H2L4) have been demonstrated to react with selected heterocyclic nitrogen donor bases to generate extended supramolecular architectures whose structures have been confirmed by X-ray diffraction. Thus on reaction with 4,4'-bipyridine (bipy), [Cu3(L2)3] yields polymeric structures of type {[Cu3(L2)3(bipy)(THF)] x 2.75THF}n and {[Cu3(L2)3(bipy)(THF)] x bipy x 0.75THF}(n) while with pyrazine (pyz), {[Cu3(L2)3(pyz)] x 0.5THF}n was obtained. Each of these extended structures contain alternating triangle/linker units in a one-dimensional polymeric chain arrangement in which two of the three copper sites in each triangular 'platform' are formally five-coordinate through binding to a heterocyclic nitrogen atom. Interaction of the multifunctional linker unit hexamethylenetetramine (hmt) with [Cu3(L3)3] afforded an unusual, chiral, three-dimensional molecular framework of stoichiometry [Cu3(L3)3(hmt)]n. The latter incorporates the trinuclear units coordinated to three triply bridging hmt units. In marked contrast to the formation of the above structures incorporating bifunctional linker units and five-coordinate metal centres, the trinuclear platform [Cu3(L2)3] reacts with the stronger difunctional base 1,4-diazabicyclo[2.2.2]-octane (dabco) to yield a highly symmetric trigonal columnar species of type {[Cu3(L4)3(dabco)3] x 3H2O}n in which each copper centre is octahedrally coordinated.     

Conjugated addition of cyanotrimethylsilane to α,β-unsaturated ketones

Triethylaluminium-mediated reaction of cyanotrimethylsilane with 6-methylbicyclo[4.4.0]dec-1-en-3-one affords a mixture of diastereomeric 1,4-adducts. The reaction is kinetically controlled in toluene, whereas thermodynamically in refluxing THF. 4-Methyl-3-penten-2-one and carvone analogously give the respective 1,4-adducts and a conjugated dienone addords the 1,6-adduct in good yield.     

An NMR and quantum-mechanical investigation of tetrahydrofuran solvent effects on the conformational equilibria of 1,4-butanedioic acid and its salts

Vicinal proton-proton NMR couplings have been used to compare the influences of water and tetrahydrofuran (THF) as solvents on the conformational equilibria of 1,4-butanedioic (succinic) acid and its mono- and dianionic salts. An earlier NMR investigation (Lit, E. S.; Mallon, F. K.; Tsai, H. Y.; Roberts, J. D. J. Am Chem. Soc. 1993, 115, 9563-9567) showed that, in water, the conformational preferences for the gauche conformations for butanedioic acid and its monoanion and dianion were, respectively, approximately 84%, 66%, and 43%, essentially independent of the nature of the cation or concentration. We now report the corresponding gauche percentages calculated in the same way for 0.05 M solutions in THF to be 66%, 90-100%, and 46-64%. Substantial evidence was adduced for the rotational angle between the substituents in the monoanion being approximately 70 degrees. The positions of conformational equilibria of the salts in THF, particularly of the dianion, were found to be rather insensitive to concentration and temperature, but more sensitive to the amount of water present. Ab initio quantum-mechanical calculations for 1,4-butanedioate dianion indicate that, as expected for the gas phase, the trans conformation of the dianion should be heavily favored over the gauche, but, in both THF and water, the gauche conformation is calculated to predominate with rotational angles substantially less than 60 degrees. This conclusion is, in fact, generally consistent with the experimental vicinal proton couplings, which are wholly inconsistent with the trans conformation.     

Synthesis of a soluble conjugated cumulene polymer: poly(biphenyl‐4,4′‐diyl‐1,4‐bis(4‐dodecyloxyphenyl)‐buta‐1,2,3‐triene‐1,4‐diyl)

A conjugated polymer with a butatriene segment in the main chain, poly(biphenyl‐4,4′‐diyl‐1,4‐bis(4‐dodecyloxyphenyl)buta‐1,2,3‐triene‐1,4‐diyl), was synthesized from 1,4‐bis(4‐bromophenyl)‐1,4‐bis(4‐dodecyloxyphenyl)buta‐1,2,3‐triene by dehalogenative polycondensation using Ni(cod)₂. The polymer was well soluble in usual organic solvents such as CHCl₃ and THF. Structural analyses and characterizations were carried out by IR, NMR, UV‐Vis, PL, and Raman spectroscopy, as well as electrical conductivity. It is suggested that π‐conjugation is extended to some degree through biphenylylene and butatrienylene linkages.     

Nickel-catalyzed indium(I)-mediated double addition of aldehydes to 1,3-dienes

In the presence of InI, Ni(acac)2 and PPh3, several 1,3-dienes were reacted with two molecules of aldehyde to give the corresponding 1,4- and 1,6-diols. The regioselectivity of the 1,4-/1,6-diol was efficiently regulated by the addition of water; the 1,6-diol was obtained selectively in dry THF, whereas the 1,4-diol was obtained predominantly in DMI containing a small amount of water.     

Microwave-assisted direct addition of cycloethers to alkynes

Under microwave conditions, tetrahydrofuran (THF), tetrahydropyran and 1,4-dioxane are added directly onto alkynes and generated various vinyl cycloethers.     

Anionic Polymerization and Copolymerization of Hydrocarbon Monomers Catalyzed by Organobarium Initiators

The barium salt of the dimeric dianion of 1,1-diphenylethylene (Ba-DPhE) initiates polymerization and copolymerization of monomers capable of anionic polymerization (butadiene, isoprene, styrene) in ethereal and hydrocarbon solvents. Ba-DPhE is more stereospecific in butadiene polymerization (up to 70% of cis-1, 4-units in hydrocarbon medium) than initiators based on other metals of Groups I and II. The relative reactivity of monomers in copolymerization processes in THF decreases in an order typical for anionic polymerization: styrene > butadiene > isoprene. The most interesting feature of organobarium initiators is their ability to form random butadiene-styrene copolymers with high cis-1,4-butadiene unit content when copolymerization proceeds in a hydrocarbon medium.

A new phenomenon in anionic polymerization, the dependence of diene units structure on copolymer composition, was observed. Thus an increase of styrene content in butadienestyrene copolymer leads to conversion of cis-1,4-butadiene units into trans-1,4-units (in benzene) or to conversion of 1,4-units to 1,2-units (in THF). Similarly, an increase of butadiene content in its copolymer with isoprene (in benzene) leads to conversion of cis-1,4-isoprene units into trans-1,4-units.

Spectrophotometric, conductometric, and viscometric methods were used to study organobarium active centers. Certain anomalies connected with the formation of specific aggregates due to coupling of bifunctional hydrocarbon chains with bivalent counterions were observed.     

1,4-Dihydroxyoctaphenyltetrasilane,a stable polysilane-α,ω-diol

1,4-Dihydroxyoctaphenyltetrasilane is obtained in 60% yield by treating a solution of 1,4-dichlorooctaphenyltetrasilane in THF with dilute HCl. Spectroscopic properties of the title compound are reported together with an X-ray structure determination, which shows that there is an intramolecular hydrogen bond between the 2 OH groups. This structural feature accounts for the ease with which the compound loses water to form the heterocyclic siloxane octaphenyloxacyclopentasilane.     

Réactivité des dérivés organocuivreux vis-à-vis des aldéhydes αβ-éthyléniques

Secondary lithium dialkylcuprates react with αβ-ethylenic aldehydes to give a mixture of 1,2 and 1,4 addition products. Only 1,2 addition products are obtained with allylic and acetylenic cuprates whereas homallylic, phenyl and vinylic cuprates give 1,4 addition products. The $\text{1,4}\text{1,2}$ ratio also depends on the nature of the metal in the cuprate (Mg or Li). Thus chloromagnesium dimethyl cuprate, in THF, is the most favorable compound to give the 1,4 addition product.     

ROOM-TEMPERATURE REDUCTIVE DIALKYLATION OF DIETHYL NAPHTHALENEDICARBOXYLATE

ABSTRACT

The reductive dialkylation of diethyl 1,4-naphthalenedicarboxylate is achieved in high yield and moderate diastereoselectivity. In liquid ammonia at ?78°C, a 5.6 : 1 ratio of trans- to cis-1,4-dimethyl-1,4-naphthalenedicarboxylates is obtained. The reductive dialkylation can also be carried out under more convenient conditions in THF at room temperature with no loss in yield, but a two-fold loss in diastereoselectivity. The alternate method is also used to synthesize 1,4-dialkylated products from ethyl bromide and allyl bromide.     

Nuclear magnetic resonance studies of isoprenyllithium derived from 1,1-diphenyl-n-butyllithium-3,4-d5, and isoprene

The equimolar reactions of 1,1-diphenyl-n-butyllithium-3,4-d₅ (RLi) with isoprene (I) and isoprene-1,4-d₄ (Id) were carried out in benzene-d₆ quantitatively to give isoprenyllithiums, RILi and RIdLi, respectively. From the NMR spectrum of the RILi it was proposed that the isoprene unit had cis-1,4, cis-4,1 and some unknown structures in benzene-d₆. When RILi was prepared in the presence of about one equivalent of THF to RILi, the anion was considered to include an isoprene unit in cis-1,4, trans-1,4, cis-4,1, and probably 3,4 structures. The same anion was obtained even if an equimolar THF was added afterward to the RILi prepared in benzene-d₆ The RLi was reproduced by the reverse reaction from RILi, when a large excess of THF was added or the temperature of the solution was elevated. The results obtained were correlated with those of anionic polymerizations of isoprene by lithium initiators.