Reactions of 4-ethoxyflavylium, 4-ethoxychromylium,and 4-ethoxyfurochromylium salts with several amines

The reactions of 4-ethoxyflavylium, 4-ethoxychromylium, and 4-ethoxyfurochromylium salts in acidic media with several acids were investigated. In the reaction with hydrazine the furochromylium salt forms pyrazole, whereas both α,β-substituted benzopyrylium salts are converted to azines. The reaction of hydroxylamine with the flavylium salt gives a flavone oxime, whereas the reaction with the furochromylium salt gives an isoxazolylbenzofuranol.     

Plate, wire, mesh, microsphere, and microtube composed of sodium titanate nanotubes on a titanium metal template

Sodium titanate nanotube/titanium metal composites were synthesized by hydrothermal treatment of titanium metals with various morphologies such as plate, wire, mesh, microsphere, and microtube at 160 degrees C in aqueous NaOH solution and by the subsequent fixation treatment by calcination at 300 degrees C. The surface of the composite was covered with sodium titanate nanotubes with a diameter of approximately 7 nm, and the core part of the composite was titanium metal phase. The raw titanium metal acts as a template or a morphology-directing agent of micrometer size or more to arrange the nanotubes as well as a titanium source for the formation of nanotubes. The concentration of titanium species increases in the reaction solution as the dissolution of titanium metal is accelerated by the reaction between titanium and OH-. Furthermore, with an increase in concentration of titanium species in the reaction solution, the titanium species are re-precipitated as sodium titanate nanotubes onto the titanium metal. Titanium metal with a large surface area and volume can form sodium titanate nanotubes on the surface of the titanium metal, though titanium metal with a small volume and surface area tends to dissolve with the hydrothermal treatment. Even in the synthesis using titanium metal with a small volume and surface area, sodium titanate nanotubes are formed and cover the surface of the titanium metal by adding another titanium metal as a source of titanium species in the reaction solution.     

Reactions of methylpyrylium,thiapyrylium, and flavylium salts with tetracyanoethylene

The reaction of 2- or 4-methyl-2,6-diphenylpyrylium perchlorate with tetracyanoethylene (TCNE) in pyridine gives 2- or 4-(2,3,3-tricyanopropylidene)-2,6-diphenylpyran in good yield. Similar results are obtained from 2- or 4-methyl-2,6-diphenylthiapyrylium and 4-methylflavylium perchlorates. In one case a stable charge-transfer salt is isolated from the reaction of a methylene base and TCNE. The reaction mechanism of dye formation is discussed.     

Rapid,quantitative, solvent-free synthesis of medium-ring diaza heterocycles from diketene–acetone adduct and diamines

The synthesis of medium-ring heterocycles remains a challenge largely due to unfavorable energetic factors. We are reporting syntheses of 7–9-member diaza heterocycles that go to completion in 5 min, require no solvents, and are quantitative with the only byproducts being acetone and water. The reaction products could be isolated in pure form by simply placing the mixture under vacuum. The reaction sequence possesses many of the hallmarks of a click reaction.     

A large volume, portable, real-time PCR reactor

A point-of-care, diagnostic system incorporating a portable thermal cycler and a compact fluorescent detector for real-time, polymerase chain reaction (PCR) on disposable, plastic microfluidic reactors with relatively large reaction volume (ranging from 10 μL to 100 μL) is described. To maintain temperature uniformity and a relatively fast temperature ramping rate, the system utilizes double-sided heater that features a master, thermoelectric element and a thermal waveguide connected to a second thermoelectric element. The waveguide has an aperture for optical coupling between a miniature, fluorescent reader and the PCR reaction chamber. The temperature control is accomplished with a modified, feedforward, variable structural proportional-integral-derivative controller. The temperature of the liquid in the reaction chamber tracks the set-point temperature with an accuracy of ± 0.1 °C. The transition times from one temperature to another are minimized with controllable overshoots (< 2 °C) and undershoots (< 5 °C). The disposable, single-use PCR chip can be quickly inserted into a thermal cycler/reader unit for point-of-care diagnostics applications. The large reaction chamber allows convenient pre-storing of dried, paraffin-encapsulated PCR reagents (polymerase, primers, dNTPs, dyes, and buffers) in the PCR chamber. The reagents are reconstituted "just in time" by heating during the PCR process. The system was tested with viral and bacterial nucleic acid targets.     

Detailed mechanism generation. 2. Aldehydes, ketones, and olefins

Generalized reaction classes for the consumption and decomposition of aldehydes, ketones, and olefins are described. These classes are important for generating not only reactions for the consumption of the branching agents of low-temperature hydrocarbon combustion but also reactions of the oxidation of alkenes and the decomposition of cyclic ethers. These reaction classes have been extrapolated from specific reactions of existing validated mechanisms. The reaction patterns making up the class were derived by identifying the reactive center of the specific reactions and the important surrounding functional groups. The rates used currently are definitely "first guesses" based on these specific reactions. The reaction classes in this paper supplement the reaction classes derived from accepted reaction types in the previous paper in this series. The purpose of this paper is to outline a complete (with very few exceptions) set of reaction classes which describe the C(5) and C(6) products of the low-temperature and cyclic ether path in the heptane and isooctane mechanisms.     

Ruthenium-catalyzed propargylic substitution reactions of propargylic alcohols with oxygen-, nitrogen-, and phosphorus-centered nucleophiles

The scope and limitations of the ruthenium-catalyzed propargylic substitution reaction of propargylic alcohols with heteroatom-centered nucleophiles are presented. Oxygen-, nitrogen-, and phosphorus-centered nucleophiles such as alcohols, amines, amides, and phosphine oxide are available for this catalytic reaction. Only the thiolate-bridged diruthenium complexes can work as catalysts for this reaction. Results of some stoichiometric and catalytic reactions indicate that the catalytic propargylic substitution reaction proceeds via an allenylidene complex formed in situ, whereby the attack of nucleophiles to the allenylidene C(gamma) atom is a key step. Investigation of the relative rate constants for the reaction of propargylic alcohols with several para-substituted anilines reveals that the attack of anilines on the allenylidene C(gamma) atom is not involved in the rate-determining step and rather the acidity of conjugated anilines of an alkynyl complex, which is formed after the attack of aniline on the C(gamma) atom, is considered to be the most important factor to determine the rate of this catalytic reaction. The key point to promote this catalytic reaction by using the thiolate-bridged diruthenium complexes is considered to be the ease of the ligand exchange step between a vinylidene ligand on the diruthenium complexes and another propargylic alcohol in the catalytic cycle. The reason why only the thiolate-bridged diruthenium complexes promote the ligand exchange step more easily with respect to other monoruthenium complexes in this catalytic reaction should be that one Ru moiety, which is not involved in the allenylidene formation, works as an electron pool or a mobile ligand to another Ru site. The catalytic procedure presented here provides a versatile, direct, and one-step method for propargylic substitution of propargylic alcohols in contrast to the so far well-known stoichiometric and stepwise Nicholas reaction.     

Triton-B-Catalyzed,Efficient, One-Pot Synthesis of Dithiocarbazates Through Alcoholic Tosylates

A quick, efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various tosylates of primary, secondary, and tertiary alcohols with a variety of substituted hydrazines using the benzyl–trimethylammonium hydroxide (Triton-B)/CS₂ system. The reaction conditions are mild with simpler workup procedures than the reported methods.     

5,12-环氧-1,2,3,4,5,12-六氢-2-并四苯基甲基酮的合成研究

蒽环类抗生素是近年来颇受人们注意的抗肿瘤药物。其配糖体蒽环酮的化学合成也引起了有机化学工作者极大的兴趣。本工作报道了蒽环酮的重要前体——b,12-环氧-1,2,3,4,5,12-六氢-2-并四苯基甲基酮(1)的合成。 1是以2,3,5,6-四甲     

Triton-B-Catalyzed,Efficient, One-Pot Synthesis of Carbazates Through Alcoholic Tosylates

A quick, efficient, one-pot synthesis of carbazates was accomplished in high yields by the reaction of various tosylates of primary, secondary, and tert alcohols, with a variety of substituted hydrazines using the benzyltrimethylammonium hydroxide (Triton-B)/CO₂ system. The reaction conditions are mild with simpler workup procedures than the reported methods.     

Dynamic effects on the periselectivity, rate, isotope effects, and mechanism of cycloadditions of ketenes with cyclopentadiene

The cycloadditions of cyclopentadiene with diphenylketene and dichloroketene are studied by a combination of kinetic and product studies, kinetic isotope effects, standard theoretical calculations, and trajectory calculations. In contrast to recent reports, the reaction of cyclopentadiene with diphenylketene affords both [4 + 2] and [2 + 2] cycloadducts directly. This is surprising, since there is only one low-energy transition structure for adduct formation in mPW1K calculations, but quasiclassical trajectories started from this single transition structure afford both [4 + 2] and [2 + 2] products. The dichloroketene reaction is finely balanced between [4 + 2] and [2 + 2] cycloaddition modes in mPW1K calculations, as the minimum-energy path (MEP) leads to different products depending on the basis set. The MEP is misleading in predicting a single product, as trajectory studies for the dichloroketene reaction predict that both [4 + 2] and [2 + 2] products should be formed. The periselectivity does not reflect transition state orbital interactions. The (13)C isotope effects for the dichloroketene reaction are well-predicted from the mPW1K/6-31+G** transition structure. However, the isotope effects for the diphenylketene reaction are not predictable from the cycloaddition transition structure and transition state theory. The isotope effects also appear inconsistent with kinetic observations, but the trajectory studies evince that nonstatistical recrossing can reconcile the apparently contradictory observations. B3LYP calculations predict a shallow intermediate on the energy surface, but trajectory studies suggest that the differing B3LYP and mPW1K surfaces do not result in qualitatively differing mechanisms. Overall, an understanding of the products, rates, selectivities, isotope effects, and mechanism in these reactions requires the explicit consideration of dynamic trajectories.     

An effective method to prepare imines from aldehyde, bromide/epoxide, and aqueous ammonia

A three-component reaction of aldehydes, alkyl bromides, and ammonia to form imines was studied. Aqueous ammonia was applied as the nitrogen source and solvent in the reaction. For the aromatic aldehyde, the product yields are good to excellent and the reaction conditions are mild to be compatible with a range of functional groups. The reaction of aldehydes and aqueous ammonia with epoxides was also studied and imines bearing a vicinal hydroxyl group can be obtained efficiently and regioselectively. And studies showed that this method allows the synthesis of primary amines and especially 1,2-amino alcohol selectively in high yield. It is proposed that the reaction pathway might involve a key intermediate of hydrobenzamide.     

Gold-catalyzed reactions of 2-alkynyl-phenylamines with alpha,beta-enones

[reaction: see text] The gold-catalyzed reaction of 2-alkynyl-phenylamines with alpha,beta-enones represents a new general one-pot entry into C-3-alkyl-indoles by sequential reactions. Gold-catalyzed sequential cyclization/alkylation, N-alkylation/cyclization, or N-alkylation/cyclization/alkylation reactions leading to different indoles can be directed by changing the 2-alkynyl-phenylamine 1/alpha,beta-enone 3 ratio and the reaction temperature. Unusual gold-catalyzed rearrangement reaction of indoles are observed at 140 degrees C. New gold-catalyzed formation of propargyl-alkyl ether under mild conditions and the hydration reaction of N-acetyl-2-ethynyl-phenylamine are reported.     

A mechanism of addition of a new aromatic electrophile,nitrobenzofuroxan, to cyclopentadiene

The reaction mechanisms of cycloaddition of nitrobenzofuroxan to cyclopentadiene are studied using DFT calculations at the B3LYP/6-31G* level in the gas phase and with account of the solvation effects. The reaction follows a three-step mechanism and includes the formation of a prereaction donor-acceptor complex, endo [4+2] cycloaddition with inverse electron demands (IED), and [3,3]-sigmatropic rearrangement to the final endo [2+4] adduct. No formation of stable bipolar σ-complexes on the minimum-energy reaction pathways occurs.     

Dicarbonyl chelates from 1-cymantrenylalkylamides with the dendrite structure: formation,photochromism, and kinetics of dark reaction with carbon monoxide

Photolysis of carboxamides of the dendrite structure with aminomethyland 1-aminoethylcymantrenes leads to the formation of six-membered dicarbonyl chelates with the Mn—O bond which are stable in solutions. The chelates in the reversed dark reaction with carbon monoxide give the starting tricarbonyl complexes. The formation of the chelates and their dark reaction are accompanied by the reversible change of color by the compounds. The rate determining step of the thermal reaction of chelates with CO is a chelate ring opening with the ligand substitution by the S_N1 mechanism. A possibility of solvent-free photoinduced ligand-exchange reaction in a number of cymantrene derivatives was demonstrated.     

Comparison of thermokinetic data obtained by isothermal, isoperibolic, adiabatic and temperature programmed measurements

In this paper isothermal, isoperibolic and adiabatic calorimeters and a Power-Compensating DSC are compared by determining kinetic data of a simple test reaction. First, the kinetic parameters were analyzed using a conventional isothermal method, based on the analytic determination of the course of reaction. Subsequently, the kinetic data of the performed reaction were determined for the different types of calorimeters by simultaneously evaluating several measurements with identical initial conditions but different temperature courses. The kinetic parameters obtained by the different calorimeters agree reasonable well, indicating the reliability of kinetic data derived from thermokinetic methods.The authors are thankful for the financial support by the Department of Education and Research of the Federal Republic of Germany (BMBF).     

Development of a novel, highly efficient halide-catalyzed sulfenylation of indoles

[reaction: see text] The reaction of a variety of indoles with N-thioalkyl- and N-thioarylphthalimides to produce 3-thioindoles is reported. Catalytic quantities of halide-containing salts are crucial to the success of this reaction. This highly efficient reaction provides sulfenylated indoles from bench-stable, readily available starting materials in good to excellent yields.     

Structural studies on cycloadducts of furan, 2-methoxyfuran, and 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide

The early stages of the retro-Diels-Alder reaction are clearly apparent in the structures of the cycloadducts formed between furan or 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide. The degree of lengthening of the C-C bonds that break in this reaction is clearly related to the known reactivity of these cycloadducts toward this reaction. In the structures of the cycloadducts 21 and 22 derived from 2-methoxyfuran, the early stages of an alternative fragmentation reaction are apparent, consistent with the reactivity of these compounds in solution.     

Copper-catalyzed hydrative amide synthesis with terminal alkyne, sulfonyl azide, and water

It is shown for the first time that N-sulfonyl amides can be efficiently prepared by an unconventional approach of the hydrative reaction between terminal alkynes, sulfonyl azides, and water in the presence of copper catalyst and amine base under very mild conditions. The present route is quite general, and a wide range of alkynes and sulfonyl azides are readily coupled catalytically with water to furnish amides in high yields. A variety of labile functional groups are tolerated under the conditions, and the reaction is regioselective in that only terminal alkynes react while double or internal triple bonds are intact. The reaction can be readily scaled up and is also adaptable to a solid-phase procedure with high efficiency.     

Polyethylene glycol in water: Simple,efficient, and catalyst-free synthesis of 4H-pyran derivatives

A green, one-pot, multicomponent method for the synthesis of diverse library of 4H-pyran derivatives such as 4-phenyl-4H-pyrans, spirochromenes, and dihydropyrano[3,2-c]chromines was developed using polyethylene glycol (PEG-600) as promoting reaction medium in water. The 4-phenyl-4H-pyran dihydropyrano[3,2-c]chromine derivatives were synthesized by a three-component reaction of aromatic aldehyde, malononitrile, and cyclic 1,3-dione/4-hydroxy coumarin at room temperature and reflux respectively. The promising points for the present methodology are efficiency, generality, high yield, short reaction time, cleaner reaction profile, ease of product isolation, potential to recycle reaction medium, and agreement with green chemistry protocols, making it a useful and attractive process for the synthesis of 4H-pyran derivatives.