Kinetics and mechanism of the N7-hydroxyalkylation of guanosine

The kinetics of the N₇-hydroxyalkylation of guanosine by the equally substituted epoxide, trans-2,3-epoxybutane, and the unequally substituted epoxides, 3-chloro-1,2-epoxypropane, and 1,2-epoxypropane in glacial acetic acid, have been measured by a spectrophotomeric method over the range 20-40°. Activation parameters have been determined. Comparative rates calculated from the ratios of second-order rate constants indicate that 1,2-epoxypropane reacts with guanosine about three times faster than does trans-2,3-epoxybutane and about two times faster than 3-chloro-1,2-epoxypropane. These results coupled with the results of a previous report on the structural analysis of the products from these reactions are consistent with a “push-pull” mechanism in which N₇ of guanosine reacts preferentially at the least substituted carbon of the epoxide with simultaneous transfer of a proton from acetic acid to the oxygen of the epoxide. The lower reactivities of trans-2,3-epoxybutane and 3-chloro-1,2-epoxypropane in comparison to that of 1,2-epoxypropane are discussed in terms of steric factors and electronic factors which determine the stability of the requisite transition state for a “push-pull” mechanism model.     

Alkylation of pyridinecarbaldehyde oximes with epoxy compounds

O-and N-Alkylation products were obtained by reactions of pyridine-2-,-3-, and-4-carbaldehyde oximes with enantiomerically pure and racemic epoxy compounds (1,2-epoxypropane, 1-phenyl-1,2-epoxyethane, 1-chloro-2,3-epoxypropane, and 1-bromo-2,3-epoxypropane) in the presence of bases and under conditions of phase-transfer catalysis. A series of new amino alcohols was synthesized by condensation of amines with products of O-alkylation of pyridinecarbaldehyde oximes with 1-halo-2,3-epoxypropanes. Published in Russian in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 3, pp. 450–454. The text was submitted by the authors in English.     

固相萃取-高效液相色谱-串联质谱测定水中8种双酚-二环氧甘油醚

建立了水中8种双酚-二环氧甘油醚（双酚A二缩水甘油醚（BADGE）及其衍生物双酚A（3-氯-2-羟丙基）甘油醚（BADGE·5HCl）、双酚A双（3-氯-2-羟丙基）醚（BADGE·52HCl）、双酚A（2,3-二羟丙基）甘油醚（BADGE·5H₂O）、双酚A双（2,3-二羟丙基）醚（BADGE·52H₂O）、双酚A（3-氯-2-羟丙基）（2,3-二羟丙基）醚（BADGE·5HCl·5H₂O）和双酚F-二环氧甘油醚（BFDGE）及其衍生物双酚F双（3-氯-2-羟丙基）醚（BFDGE·52HCl））的固相萃取-高效液相色谱-串联质谱（SPE-HPLC-MS/MS）测定方法。10个饮用水接触涂料样品在室温避光条件下,以超纯水浸泡（24±1）h,然后取200 mL经C₁₈固相萃取柱进行净化浓缩,以C₁₈色谱柱进行分离,以5 mmol/L醋酸铵、甲醇和水为流动相进行梯度洗脱,质谱多反应监测（MRM）模式检测,外标法定量。结果表明,8种双酚-二环氧甘油醚在0.007~5.00 μg/L线性关系良好,相关系数均大于0.9990,该方法对8种双酚-二环氧甘油醚的定量限为7~91 ng/L,回收率为79.1%~101%,RSD为4.0%~12%。该方法具有灵敏度高、选择性强的特点,能够满足水中双酚-二环氧甘油醚的快速检测和准确定量。     

Palladium-catalyzed reaction of methyl 5-amino-4-chloro-2-methylthiopyrrolo[2,3-<Emphasis Type="Italic">d</Emphasis>]-pyrimidine-6-carboxylate with arylboronic acids. Synthesis of 1,3,4,6-tetraazadibenzo[<Emphasis Type="Italic">cd,f</Emphasis>]-azulene heterocyclic system

Densely substituted methyl 5-amino-4-aryl-7-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine-6-carboxy- lates were synthesized by the palladium-catalyzed cross-coupling reaction of methyl 5-amino-4-chloro-7-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylate with arylboronic acids using Pd(OAc)₂/dicyclohexyl(2-biphenyl)phosphine/K₃PO₄ as a catalyst system. Reaction of methyl 5-amino-4-chloro-7-methyl-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylate with 2-formylphenyl- boronic acid led to a novel heterocyclic system – 1,3,4,6-tetraazadibenzo[cd,f]azulene.     

Reaction of 1,2,4-triazole-3-thiones with 1-chloro-2,3-epoxypropane

Addition of 1-chloro-2,3-epoxypropane to 1,2,4-triazole-3-thiones depending on the ratio of the reactants leads to the formation of 3-(1-chloro-2-hydroxypropyl)-3-(1-chloro-2-hydroxypropylthio)-1,2,4-triazoles. 3-Hydroxy-1,2,4-triazolo[2,3-b] tetrahydro-1,3-triazines have been synthesized by intramolecular cyclization of the monoadducts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 271–274, February, 1987     

Effect of the structure of carboxylic acids on activation parameters for catalytic acidolysis of epichlorohydrin

We have studied the effect of temperature and the structure of the reagent on the rate of the reaction between 1-chloro-2,3-epoxypropane (epichlorohydrin) and aliphatic monocarboxylic acids in the presence of an ammonium salt: (3-chloro-2-hydroxypropyl)trimethylammonium chloride, obtained from trimethylammonium chloride and epichlorohydrin. We have done a correlation analysis of the effect of the substituent within the structure of the carboxylic acid and the temperature on the reaction rate. Using ab initio quantum chemical methods, we have estimated the structures and energy parameters of the transition states for the limiting step of the process, and have formulated hypotheses for the reaction mechanism.     

The kinetics and mechanism of the reaction between 1-chloro-2,3-epoxypropane and p-cresol in the presence of basic catalysts

Rate constants for the reaction of 1-chloro-2,3-epoxypropane with p-cresol in the presence of basic catalysts were studied at the temperature range of 71–100°C. It was found that in the presence of sodium p-cresolate, three consecutive reactions proceeded giving the following products: 1-chloro-3-(tolyloxy)-2-propanol (CTP), 1-(p-tolyloxy)-2,3-epoxypropane (TEP) as a main product, and 1,3-di(p-tolyloxy)-2-propanol (DTP). Their rate constants at 71°C were: k₁ = 0.030 ± 0.009, k₂ = 1.58 ± 0.02, and k₃ = 0.033 ± 0.005 dm³/mol · min, respectively. In the presence of quaternary ammonium salts, this process consisted of 5 reactions which led to CTP as a main product as well as TEP and 1,3-dichloro-2-propanol (DCP). The rate constant of CTP formation at 71°C was established, k₁ = 0.130 ± 0.030 dm³/mol · min, as were the ratios of the other rate constants k₂/k₋₄ = 1.5 ± 0.2, k₅/k₋₄ = 20.0 ± 5.0, and k₄/k₁ = 0.6 ± 0.7. Based on the changes in Cl⁻ ion concentration during the reaction, the catalystic activity of quaternary ammonium salts was explained. The kinetic model of these reactions in the presence of basic catalysts has been proposed and appropriate kinetic equations have been presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 73–79, 1997.     

Syntheses on the basis of diethyl (2-morpholinoethyl)malonate

New functionally substituted butan-4-olides were synthesized by reactions of diethyl (2-morpholinoethyl) malonate with 2-(allyloxymethyl)oxirane, 4-(oxiran-2-ylmethyl)morpholine, N-ethyl-N-(oxiran-2-ylmethyl)aniline, and 1-chloro-2,3-epoxypropane. 5-[2-(Morpholino)ethyl]barbituric and -thiobarbituric acids were also synthesized.     

Peculiarities of catalytic behavior of bases in the reaction of aliphatic carboxylic acids with epoxide

A study was carried out on the kinetics of the reaction of 1-chloro-2,3-epoxypropane (epichlorohydrin, ECH) with aliphatic carboxylic acids in the presence of (3-chloro-2-hydroxypropyl)trimethylammonium (CHPTMA) chloride obtained by trimethylammonium chloride and ECH. We compared the catalytic activity of CHPTMA chloride, trialkylamines, and tetraalkylammonium halides and evaluated the effect of their structure. An ab initio quantum-chemical calculation was performed to obtain a detailed analysis of the state of the catalysts in this system in order to understand the peculiarities of catalytic activity of these bases. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 292–297, September–October, 2008.     

Features of the reaction of polyfluoroalkyl chlorolsulfites with allyl alcohol

Unlike the saturated aliphatic and aromatic alcohols, allyl alcohol under the same conditions reacts with polyfluoroalkyl chlorosulfites to form not ethers, but polyfluorinated alcohols. The exception is polyfluoroalkyl chlorosulfites with the chain length of more than five carbon atoms. Allyl ethers of polyfluorinated alcohols of general formula CH₂=CHCH₂OCH₂(CF₂CF₂)nH (n = 1–3) were obtained, when the reaction proceeded in the presence of potassium carbonate, owing to its participation in a specific orientation of the reaction centers in the resulting intermediate structure, which is easily transformed into allyl ethers of polyfluorinated alcohols.     

Biodegradable Polycarbonate Synthesis by Copolymerization of Carbon Dioxide with Epoxides Using a Heterogeneous Zinc Complex

As a means for the chemical fixation of carbon dioxide and the synthesis of biodegradable polycarbonates, copolymerizations of carbon dioxide with various epoxides such as cyclohexene oxide (CHO), cyclopetene oxide, 4-vinyl-1-cyclohexene-1,2epoxide, phenyl glycidyl ether, allyl glycidyl ether, propylene oxide, butene oxide, hexene oxide, octene oxide, and 1-chloro-2,3-epoxypropane were investigated in the presence of a double metal cyanide catalyst (DMC). The DMC catalyst was prepared by reacting K₃Co(CN)₆ with ZnCl₂, together with tertiary butyl alcohol and poly(tetramethylene ether glycol) as complexing reagents and was characterized by various spectroscopic methods. The DMC catalyst showed high activity (526.2 g-polymer/g-Zn atom) for CHO/CO₂ (P_CO2 = 140 psi) copolymerization at 80 °C, to yield biodegradable aliphatic polycarbonates of narrow polydispersity (M_w/M_n = 1.67) and moderate molecular weight (M_n = 8900). The DMC catalyst also showed high activities with different CO₂ reactivities for other epoxides to yield various aliphatic polycarbonates with narrow polydispersity.     

Iridium‐Catalyzed Intermolecular Asymmetric Dearomatization of β‐Naphthols with Allyl Alcohols or Allyl Ethers

An Ir‐catalyzed intermolecular asymmetric dearomatization reaction of β‐naphthols with allyl alcohols or allyl ethers was developed. When an iridium catalyst generated from [Ir(COD)Cl]₂ (COD=cyclooctadiene) and a chiral P/olefin ligand is employed, highly functionalized β‐naphthalenone compounds bearing an all‐carbon‐substituted quaternary chiral center were obtained in up to 92 % yield and 98 % ee . The direct utilization of allyl alcohols as electrophiles represents an improvement from the viewpoint of atom economy. Allyl ethers were found to undergo asymmetric allylic substitution reaction under Ir catalysis for the first time. The diverse transformations of the dearomatized product to various motifs render this method attractive.     

The Cp2ZrCl2-catalyzed cycloalumination of functionally substituted olefins with triethylaluminum

Reactions of functionally substituted olefins (allylamines, sulfides and ethers, homoallylic alcohols and amines, as well as vinyl ethers) with Et₃Al in the presence of Cp₂ZrCl₂ as a catalyst were studied. Cycloalumination of allylamines occurs with high regioselectivity to furnish after subsequent deuterolysis 4-deutero-2-(deuteromethyl)butyl-substituted amines. Cycloalumination of alkyl allyl sulfide is accompanied by a side process of the C-S bond cleavage. In the case of allyl and vinyl ethers, no cycloalumination products are formed under the reaction conditions. However, the reactions with homoallylic alcohol and amine after deuterolysis gave the corresponding dideutero-containing compounds in good yields.     

Cerium ammonium nitrate (CAN) for mild and efficient reagent to remove hydroxyethyl units from 2-hydroxyethyl ethers and 2-hydroxyethyl amines

Cerium ammonium nitrate (CAN) removed hydroxyethyl units from 2-hydroxyethyl ethers and 2-hydroxyethyl amines to produce alcohols and amines in good yields. Especially, removal of the 2-hydroxyethyl ethers from C₂-symmetric diols, chiral 2,3-butanediol and chiral hydrobenzoin, was very useful for asymmetric syntheses using C₂-symmetric diols. The reactions using dual abilities of CAN, i.e., the ability for removal of the 2-hydroxyethyl unit and the ability for acetal hydrolysis by a single electron transfer, were also achieved successfully. The reaction conditions were very mild and efficient, and many functional groups, which can be affected under normal conditions, were unaffected during the reaction.     

Synthesis of 2,3-di(ω-hydroxyalkyl)quinolines from anilines and cyclic enols using sequential cycloaddition/aromatization reactions

A new synthetic protocol for the one-pot synthesis of 2-(4-hydroxybutyl)-3-(3-hydroxypropyl)quinolines and 3-(2-hydroxyethyl)-2-(3-hydroxypropyl)-quinolines based in the AB² imino-Diels-Alder reaction is reported. The protocol describes simple and efficient preparation of 2,3-disubstituted quinolines using a domino-sequential process and applying the chemical properties of cyclic enol ethers, such as 2,3-dihydrofuran and 3,4-dihydro-2H-pyran and diverse arylamines, through an imino-Diels-Alder process between an in situ generated 2-azadiene and another equivalent of the cyclic enol, catalyzed by BiCl₃, and followed by the aromatization (oxidation) process guided by the MnO₂.     

Selective tetrahydropyranylation of alcohols and phenols using titanium(IV) salophen trifluoromethanesulfonate as an efficient catalyst

Titanium(IV) salophen trifluoromethanesulfonate, [Ti^IV(salophen)(OSO₂CF₃)₂], as a catalyst enables selective tetrahydropyranylation of alcohols and phenols with 3,4‐dihydro‐2H‐pyran. Using this catalytic system, primary, secondary and tertiary alcohols, as well as phenols, were converted to their corresponding tetrahydropyranyl ethers in high yields and short reaction times at room temperature. Investigation of the chemoselectivity of this method showed discrimination between the activity of primary alcohols in the presence of secondary and tertiary alcohols and phenols. This heterogenized catalyst could be reused several times without loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and photophysical properties of oligoarylenes with a pyrrolo[2,3-d]pyrimidine core

The palladium-catalyzed Suzuki-Miyaura reaction of 2,4-dichloropyrrolo[2,3-d]pyrimidine with aryl boronic acids has been studied. Pd(OAc)₂/dicyclohexyl(2-biphenyl)phosphine/K₃PO₄ was found to be an efficient catalyst system to prepare 4-aryl-2-chloro- and 2,4-diarylpyrrolo[2,3-d]pyrimidines. Novel non-linear molecules consisting of a pyrrolo[2,3-d]pyrimidine core and aryl branches have been elucidated as blue light-emitters with fluorescence quantum yields ranging from 4% to 67% in THF solution. The impact of an electron-withdrawing t-BuOCO group attached to the pyrrole ring of pyrrolopyrimidine derivatives on optical properties is discussed.     

A Mild,Simple, Efficient,and Selective Protection of Hydroxyl Groups Using Silica-Supported Sodium Hydrogen Sulfate as a Heterogeneous Catalyst

A mild, simple, novel, and highly efficient method for the rapid protection of various primary, secondary, tertiary aliphatic alcohols, aromatic alcohols, and oximes using hexamethyldisilazane (HMDS) in the presence of silica-supported sodium hydrogen sulfate (NaHSO ₄ -SiO ₂ ), as an active, inexpensive, nontoxic, heterogeneous, and readily available catalyst under ambient conditions is described. Timethylsilyl ethers were prepared in high to excellent yields, with short reaction times under mild and almost neutral reaction conditions at room temperature.     

Palladium-catalyzed oxime ether directed regioselective C-H alkoxylation of arenes

A palladium-catalyzed highly regioselective ortho-C(sp²)-H alkoxylation of oxime ethers with PhI(OAc)₂ as the oxidant and alcohols as the alkoxylation reagents has been developed. Mono-alkoxylated and acetoxylated products could be selectively obtained via tuning the reaction conditions. A series of oxime ethers were tolerated, affording the corresponding products in moderate to good yields. Both primary and secondary alcohols survived the reaction conditions. Moreover, the directing group can be easily removed, thereby providing a straightforward access to substituted aryl ketones.     

Oxidation of Alcohols and Pyridines by a Water-Soluble Polyoxometalate with Hydrogen Peroxide

A water-soluble catalyst based on a silicotungstate polyoxometalate, K₈[β-SiW₁₁O₃₉] · 14H₂O, was developed for the oxidation of pyridines and alcohols with hydrogen peroxide. The reactions were carried out in water, and good yields of the corresponding heterocyclic N-oxides and ketones were obtained under relatively mild conditions. The catalyst could be easily recovered by extraction with ethyl acetate and reused several times.

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