Cyclodehydration of diphenyl-trifluoromethyl-carbinols

The halochromic product from di-(p-fluorophenyl) -trifluoromethylcarbinol and sulphuric acid gives with ethyl mercaptan 3-ethylthio-6 fluoro-9-trifluoromethylfluorene. Analogous reactions have been observed with (p-chlorophenyl)-(p-fluorophenyl)-, with (p-fluorophenyl)-phenyl-. and with diphenyl-trifluoromethyl-carbinol.

The infra-red spectra of the fluorene derivatives formed are discussed.     

吴茱萸次碱和喹唑酮类化合物的合成

吴茱萸次碱;喹唑酮;Diels-Alder反应     

Acid-Catalyzed Hydration of anti-Sesquinorbornene

The acid-catalyzed hydration of anti-sesquinorbornene (1) has been studied at 25 degrees C in 20% DME/H(2)O from 0.001 M < [HC1] < 0.05 M. The second-order rate constant for hydration is 5.35 +/- 0.07 M(-)(1) s(-)(1) which can be compared with a value of 1.38 +/- 0.06 M(-)(1) s(-)(1) for ethyl vinyl ether determined under the same conditions. The solvent deuterium kinetic isotope effect for hydration of 1 is 2.7, and a plot of the observed second-order rate constant for the hydration in a mixed solvent system of H(2)O/D(2)O against the atom fraction of deuterium (n) is bowed upward. The reaction also shows marked buffer catalysis by formic, chloroacetic, and dichloroacetic acids, the Br?nsted alpha being 1 for these three carboxylic acids: H(3)O(+) does not fit on this Br?nsted line. A mechanism for the reaction is presented which is consistent with the generally accepted one for acid-catalyzed hydration of an alkene in which the rate-limiting step involves proton transfer from H(3)O(+) to the double bond. Whether attack of a second water on the developing carbocation occurs simultaneously with protonation cannot be ascertained from the data for 1, but if so, the extent of its C-OH(2) bond formation must be small enough that there is little change in the bonding of these O-H bonds.     

1,4-丁二醇气相环化脱水合成四氢呋喃

以1,4-丁二醇为原料,采用气相环化脱水法合成了四氢呋喃.考察了催化剂(γ-Al2O3,ZrO2,CeO2和ZSM-5),反应温度,进料速率和反应时间等因素对环化脱水反应的影响.结果表明,在以γ-Al2O3为催化剂,进料速率为2.4 mL*min-1,于320 ℃反应2 h的最佳反应条件下,1,4-丁二醇的转化率接近100%,四氢呋喃的选择性达99.8%.     

Preparation and Properties of Epoxy Resins Containing Quinazolone Rings

Epoxy resins containing quinazolone rings were synthesized and characterized. Epoxy resins were made by reacting bisquinazolone phenol or bisquinazoline with epichlorohydrin or the diglycidyl ether of Bisphenol A. These resins were analyzed by DSC, GPC, IR, and NMR. The electrical and mechanical properties of the cured resins were evaluated. They have glass transition temperature above 200°C and excellent thermal stability, and T_g increases in the order of o-, m-, p-substituted phenol groups.     

Acid-Catalyzed Diels-Alder Reactions of Cycloalkenones

Whereas the Diels-Alder reaction has been in vogue as a facile method of six-membered ring construction for many years, its application to a one-step cis-octalone synthesis was precluded by discouraging, early reports on the conditions required for the interaction of dienes with 2-cyclohexenones and on the yields of the resultant adducts.^1,2 It is quite conceivable that these observations were responsible in part for the minimization of use of an otherwise attractive route toward angularly alkylated six-membered polycycles in the field of steroid total synthesis. The discovery of Lewis acid catalysis of the cycloaddition of α, β-unsaturated carbonyl compounds³ has rekindled interest in the above reactions.⁴ The following discussion illustrates octalone     

Acid-Catalyzed Amine-Borane Reduction of Nitrite

The rate of reduction of nitrite by trimethylamine-borane was followed by observing the decrease in nitrite absorbance under pseudo-first-order conditions. The reaction is acid-catalyzed and exhibits a first-order dependence on both amine-borane and total nitrite concentration. The molar equivalence of NaNO(2) to (CH(3))(3)NBH(3) = 2:1. Equimolar amounts of hydrogen and nitrous oxide are formed, and the molar ratio of nitrite reacted to N(2)O produced is 2:1. In concentrated HCl or H(2)SO(4), a correlation of rate with the Hammett acidity function, h(o), is observed. The reaction is subject to a pronounced inversesolvent isotope effect (k(D)()2(O)/k(H)()2(O) approximately 2.7) and a modest normal substrate effect (k((CH)()3())()3(N.BH)()3/k((CH)()3())()3(N.BD)()3 approximately 1.4). The reaction is first-order in H(3)O(+) in the region pH 0.7-2.7, but a second-order dependence is observed above pH 4 with the transition occurring at pH approximately pK(a) for HNO(2). Results are consistent with a mechanistic model involving preequilibration protonation of molecular nitrous acid followed by rate-limiting hydride attack on H(2)ONO(+) or free NO(+) to produce nitrosyl hydride as a reactive intermediate.     

Functionality and Functionality Distribution Measurements of Binder Prepolymers

Abstract

The functionality of a prepolymer, which is defined as the ratio of molecular weight to equivalent weight, is probably the most important single parameter that determines the properties of the cross-linked polymer network. The determination of prepolymer functionality therefore requires accurate knowledge of both number average molecular weight and equivalent weight. Ideally, a suitable prepolymer for propellant binder applications has terminal functionality (OH or COOH). Such a prepolymer theoretically has a functionality of 2.0. Because of uncontrolled chain termination reactions during the prepolymer synthesis, however, not all polymer chains have the desired functional end group. As a result, prepolymers generally have a distribution of functionalities, including onfunctional, monofunctional, and the desired difunctional prepolymer.     

The Synthesis of Some New Quinazolone Derivatives of Potential Biological Activity

The refluxing of 3-amino-6,8-dibromo-2-thioxo-2,3-dihydro-1H-quinazolin-4-one (5) with ethyl chloroformate and/or ethyl chloroacetate afforded compounds 6 and 7 . The reaction of 5 with ethyl bromobutyrate, chloroacetyl chloride, phenacyl chloride, and phenyl isocyanate yielded compounds 8 , 9 , 11 , and 12 . The coupling of 5 with (2,3,4,6-tetra-O-acetyl-α -D-gluopyranosyl)bromide( ABG ) in DMF at r.t. gave 3-amino-6,8-dibromo-2-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyl)thioxo-2,3-dihydro-1H-quinazolin-4-one ( 14 ). The deblocking of 14 in sodium methoxide gave 5 . 3-Amino-6,8-dibromo-2-methylthio-3H-quinazolin-4-one ( 16 ) was prepared by stirring 5 with methyl iodide in methanol. The treatment of 16 with hydrazine hydrate afforded 4 . The condensation of 4 with aldehydes furnished 3,5-dibromo-2-arylaminobenzoic acid hydrazide ( 18a–c ). The refluxing of 18a with acetic anhydride gave 3-(benzylideneamino)-6,8-dibromo-2-methyl-3H-quinazolin-4-one ( 19 ). Hydrazones 20a–f were prepared by the condensation of 4 with pentoses and/or hexoses. The acetylation of ( 20a–f ) with acetic anhydride gave the acetyl derivatives 21a–f .     

Energetics of the Acid-Catalyzed o-Cresol-Formaldehyde Reaction

The acid-catalyzed reaction of o-cresol with formaldehyde follows second-order kinetics. The reaction was carried out at 65, 70, 75, and 80°C and at pH values of 1.30, 1.80, 2.00, 2.50, and 3.00, using hydrochloric acid as a catalyst. The rate was found to increase with decreasing pH. The overall rate constant (k) has been resolved into stepwise rate constants (k₁ and k₂) for the formation of monomethylol and methylene derivatives. Values of Arrhenius parameters and of the entropy of activation for the overall reaction were also calculated. A mechanism consistent with our kinetic data is given.     

AlPO4-Al2O3 Promoted Cyclodehydration of Diols

A convenient method for the preparation of cyclic ethers by distillation of diols over solid AlPO₄[sbnd]Al₂O₃ is presented.     

含P_H键苯并磷杂环化合物与醛反应的研究

利用含P_H键苯并磷杂环化合物与醛的反应,设计合成了新的A2羟基膦酸衍生化喹唑啉酮含磷类似物2或Ò,并研究了含P_C_O结构的2或Ò转化为含P_O_C结构的3或Ó的重排反应,目标化合物的结构经NMR,IR,MS和元素分析证实.结合NMR数据,探讨了化合物2因具有C^*和P^*两个手性中心而产生的非对映异构现象及其氢谱特征.对所合成的化合物进行了初步生物活性测试,发现部分化合物具有很好的抗植物病原真菌(苹果斑点落叶病菌)作用和一定的人体疱疹病毒抑制活性.     

α-硫羰基膦酸衍生化喹唑啉酮含磷类似物的研究

研究了两种不同的合成路线，合成１７个新的α－硫羰基膦酸衍生化喹唑啉酮含磷类似物２ａ－２ｑ，其结构经ＮＭＲ，ＩＲ，ＭＳ和元素分析表征，通过单晶Ｘ射线衍射分析，探讨了稠杂环标化合物的立体化学特征，并对其１，３位取代棋的氢谱磁不等价现象进行了合理解释。     

钼酸催化简便合成D－葡萄庚酮糖

本文首次报道了在三氧化钼水溶液体系下催化碳链重排合成D-葡萄庚酮糖的简便方法。首先以D-甘露糖为原料在碘催化下进行异丙叉保护,产率90％;接着在碱催化下与甲醛水溶液亲核加成反应,在C-2上引入羟甲基侧链,产率40％;然后在酸性条件下异丙叉脱保护,产率92％;最后在三氧化钼水溶液催化下碳链重排合成葡萄庚酮糖,产率56％（总产率18％）。另外对2-C-羟甲基-D-甘露糖和葡萄庚酮糖的乙酰化产物进行了核磁氢谱表征。该方法原料易得,缩短了反应步骤,避免了昂贵金属试剂的使用,有较好的应用前景。     

A Novel Acid-Catalyzed Isomerization of Aib-Containing Thiodipeptides

The use of amino thioacids in the `azirine/oxazolone method' led to completely epimerized Aib-containing endothiodipeptides (Aib=2-aminoisobutyric acid). It could be established that the epimerization occurred during the acidic hydrolysis of the primarily formed dipeptide thioanilides in which the thiocarbonyl group was shifted from the last to the penultimate amino-acid residue. Several conditions for the hydrolysis were tested, and, in some of them, the degree of epimerization could be reduced. By treatment of the Aib-containing dipeptide thioanilides 21 with ZnCl₂ in AcOH followed by HCl in AcOH, the isomeric endothiodipeptide anilides 25 were formed, i.e., the thiocarbonyl group was again shifted from the last to the penultimate amino acid residue. Under optimized reaction conditions, this novel isomerization proceeded in high yields and without any epimerization. Two conceivable mechanisms are proposed in Scheme 12. X-Ray diffraction analyses were performed for Z−Gly−Aib-Ψ(CS)−N(Me)Ph ( 21f ) and the isomeric Z−Gly-Ψ(CS)−Aib−N(Me)Ph ( 25f ).     

The Acid-Catalyzed Hydrolysis of Anomeric Alkyl Fructofuranosides

Abstract

The rate constants for the hydrolysis of some al-kyl α- and β-d-fructofuranosides in aqueous perchloric acid have been determined at various temperatures. The effects of varying the aglycon structure on the hydrolysis rate suggest, together with the markedly positive entropies of activation, that the substrate, protonated on the glycosidic oxygen atom, undergoes a rate-limiting unimolecular heterolysis to form a glycosyl oxocar-benium ion. The rate variations in mixtures of aqueous perchloric acid and dimethyl sulfoxide are interpreted as lending further support for the proposed mechanism.     

Acid-Catalyzed Rearrangements of (-)-Thujopsene

The transformations of (-)-thujopsene in liquid (HSO₃F-SO₂FCl) and over solid (TiO₂/SO₄ ^{2 -}) superacids, as well as by the action of peroxy acids, were studied. New tricyclic hydrocarbons were isolated. The experimental results were compared with the data of computer analysis of the most probable transformation pathways using molecular-mechanics and quantum-chemical methods.