924-41-4Relevant articles and documents
Degradation of minocycline by the adsorption–catalysis multifunctional PVDF–PVP–TiO2 membrane: Degradation kinetics, photocatalytic efficiency, and toxicity of products
Zhou, Chengzhi,Sun, Yanlong,Zhang, Fan,Wu, Yuandong
, (2021/11/30)
The photocatalytic degradation of minocycline was studied by using polyvinylidene fluoride–polyvinylpyrrolidone–TiO2 (PVDF–PVP–TiO2) fiber mats prepared by an electrospinning technology. The influences of the TiO2 dosage, minocycline concentrations, inorganic anions, pH values, and dissolved organic matter (DOM) concentrations on the degradation kinetics were investigated. A mass of 97% minocycline was degraded in 45 min at 5% TiO2 dosage. The corresponding decomposition rate constant was 0.069 min?1. The inorganic anions affected the minocycline decomposition in the order of HCO3? > Cl? > SO42? > NO3?, which was confirmed by the results of electron spin resonance (ESR) spectra. The lowest electrical energy per order (EEO) was 6.5 Wh/L. Over five cycles, there was no change in the photocatalytic performance of the degrading minocycline. Those investigations suggested that effective degradation of minocycline could be reached in the PVDF–PVP–TiO2 fiber mats with a low energy consumption, good separation and, good recovery. Three photocatalytic decomposition pathways of minocycline were proposed: (i) hydroxyl substitution of the acylamino group; (ii) hydroxyl substitution of the amide group, and (iii) a cleavage of the methyl groups and further oxidation of the amino group by OH. Potential risks caused by TP159 and TP99 should not be ignored, while the TP90 are nontoxic. Tests indicated that the toxicity of the photocatalytic process may be persistent if minocycline and its products were not mineralized completely.
Total synthesis and structure confirmation of elatenyne: Success of computational methods for NMR prediction with highly flexible diastereomers
Dyson, Bryony S.,Burton, Jonathan W.,Sohn, Te-Ik,Kim, Byungsook,Bae, Hoon,Kim, Deukjoon
supporting information; experimental part, p. 11781 - 11790 (2012/09/10)
Elatenyne is a small dibrominated natural product first isolated from Laurencia elata. The structure of elatenyne was originally assigned as a pyrano[3,2-b]pyran on the basis of NMR methods. Total synthesis of the originally proposed pyrano[3,2-b]pyran structure of elatenyne led to the gross structure of the natural product being reassigned as a 2,2′-bifuranyl. The full stereostructure of this highly flexible small molecule was subsequently predicted by Boltzmann-weighted DFT calculations of 13C NMR chemical shifts for all 32 potential diastereomers, with the predicted structure being in accord with the proposed biogenesis outlined below. Herein we report two complementary total syntheses of elatenyne, which confirm the computer-predicted stereostructure. Additionally, the total syntheses of (E)-elatenyne and a related 2,2′-bifuranyl, laurendecumenyne B, are reported. This work has not only allowed the full structure determination of all of these natural products but also provides excellent supporting evidence for their proposed biogenesis. The total synthesis of elatenyne demonstrates that DFT calculations of 13C NMR chemical shifts coupled with biosynthetic postulates, comprise a very useful method for distinguishing among large numbers of highly flexible, closely related molecules.
An efficient DABCO-catalyzed Ireland-Claisen rearrangement of allylic acrylates
Li, Yunxia,Wang, Quanrui,Goeke, Andreas,Fráter, Georg
, p. 288 - 292 (2007/10/03)
A novel DABCO-catalyzed Ireland-Claisen [3,3]-rearrangement of allylic acrylates to give α-methylene-γ,δ-unsaturated carboxylic acids in the presence of an excess of TMSCl and DBU in refluxing acetonitrile was developed. The protocol provides an easy entry to α-methylene-γ, δ-unsaturated carboxylic acids from allylic alcohols in good yields. Georg Thieme Verlag Stuttgart.
Iridium-catalyzed synthesis of primary allylic amines from allylic alcohols: Sulfamic acid as ammonia equivalent
Defieber, Christian,Ariger, Martin A.,Moriel, Patricia,Carreira, Erick M.
, p. 3139 - 3143 (2008/03/11)
(Chemical Equation Presented) Two for the price of one: Sulfamic acid serves not only as a nitrogen source but also as an in situ activator of hydroxy groups in the first direct iridium-catalyzed synthesis of primary allylic amines from allylic alcohols (see scheme; cod = cycloocta-1,5-diene). The reaction is catalyzed by a commercially available iridium complex and a phosphoramidite-based bidentate phosphorus-olefin ligand.
Novel carbonyl allylation mediated by SnCl2/Cu in water
Tan, Xiang-Hui,Shen, Bo,Liu, Lei,Guo, Qing-Xiang
, p. 9373 - 9376 (2007/10/03)
Copper metal was found to be able to catalyze SnCl2-mediated coupling between carbonyl compounds and allyl halides to give the corresponding homoallylic alcohols in high yields.
Synthesis of allyl-cyclopropyl alcohols and allyl-1,5-hexadien-3-ols and investigation of their antibacterial and antifungal activities
Servi,Cansiz,Digrak,Ahmedzade
, p. 629 - 633 (2007/10/03)
Two different methods have been used to obtain allyl-cyclopropyl alcohols and allyl-1,5-hexadien-3-ols, starting with various allyl substituted chloromethyloxiranes. While allyl substitued 1,5 - hexadien - 3 - ols are formed in reactions occurring with Mg in THF, the unsaturated cyclic alcohols are also formed. However, the reaction carried out with Na in Ch3OH gives only 1,5-dien-3-ols. Antimicrobial activity of the synthesised compounds has been tested against 16 microorganisms. The compounds have also been screened for their antibacterial and antifungal activities against bacteria, yeasts and moulds.
Palladium(II)-Catalyzed Intramolecular Aminocarbonylation of endo-Carbamates under Wacker-Type Conditions
Harayama, Hiroto,Abe, Atsuhiro,Sakado, Tomonori,Kimura, Masanari,Fugami, Keigo,Tanaka, Shuji,Tamaru, Yoshinao
, p. 2113 - 2122 (2007/10/03)
Pd(II)-catalyzed intramolecular aminocarbonylation of olefins bearing many types of nitrogen nucleophiles has been examined under two typical conditions: acidic conditions [conditions A, typically PdCl2 (0.1 equiv) and CuCl2 (3.0 equiv) under 1 atm of CO at room temperature in methanol] and buffered conditions [conditions B, typically PdCl2 (0.1 equiv) and CuCl2 (2.3 equiv) under 1 atm of CO at 30°C in trimethyl orthoacetate]. Among nitrogen nucleophiles, endocarbamates 7 display distinctive reactivity: endo-carbamates 7a-k smoothly undergo intramolecular aminocarbonylation under conditions B to furnish 4-[(methoxycarbonyl)methyl]-2-oxazolidinones 8a-k in good yields, while they would not undergo the expected reaction under conditions A. Other nitrogen nucleophiles (exo-ureas 1, endo-ureas 3, exo-carbamates 5, and exo-tosylamides 9), on the other hand, satisfactorily undergo aminocarbonylation only under conditions A to give rise to 2,4,6, and 10, respectively, in good yields. Under conditions B, they are unreactive and provide either the expected products in poor yields or intractable mixtures of products. On the basis of this contrasting reactivity between endo-carbamates and other nitrogen nucleophiles, the chemoselective aminocarbonylation of 71-o has been achieved; aminocarbonylation takes place at the endo-carbamate moieties to furnish 81-o exclusively under conditions B, and aminocarbonylation occurs at the exo-carbamate, exo-urea, and exo-tosylamide moieties to yield 13a-d exclusively under conditions A.
A Highly Effective One-Pot Bicycloannulation Methodology for the Synthesis of Berban and Yohimban Systems Based on Organotin-Mediated Three-Component Coupling (N-Acylative Pentadienylation of C=N Bonds)
Yamaguchi, Ryohei,Hamasaki, Takashi,Sasaki, Tohru,Ohta, Tetsuo,Utimoto, Kiitiro,et al.
, p. 1136 - 1143 (2007/10/02)
A highly effective bicycloannulation methodology for the synthesis of berban and yohimban alkaloid systems is described.Three-component coupling reactions of 2,4-pentadienyltin reagents with C=N bonds and α,β-unsaturated acyl chlorides furnish bicycloannulated products in a one-pot operation.For example, the reactions of 2,4-pentadienyltributyltin(1) with isoquinoline derivatives activated by acryloyl chloride afford the tetracyclic (+/-)-allo-berban systems stereoselectively.Similarly, the reaction of 1 with 3,4-dihydro-β-carboline (11) gives the pentacyclic (+/-)-allo-yohimban system.The reaction is not affected by the stereochemistry of the 2,4-pentadienyltin reagent.A new substituted 2,4-pentadienyltin reagent, 3-(hydroxymethyl)-2,4-pentadienyltrimethyltin (19), is prepared via 3-(hydroxymethyl)pentadienyl dianion.The three-component coupling reaction of 19 with 11 and acryloyl chloride affords the (+/-)-allo-16-(hydroxymethyl)yohimban system, from which (+/-)nitraraine is readily synthesized.In addition, 1,3-asymmetric induction leads to the high diastereoselectivity realized in bicycloannulation (up to 94percent de) when (S)-3--3,4-dihydroisoquinoline (27), which is readily derived from L-phenylalanine, is used in the three-component coupling reaction.
Photochemistry of 1,5-hexadien-3-ones: Wavelength-dependent selectivity in intramolecular enone-olefin photoadditions
Dauben, William G.,Cogen, Jeffrey M.,Ganzer, George A.,Behar, Victor
, p. 5817 - 5824 (2007/10/02)
The photochemistry of ten 1,5-hexadien-3-ones in methanol is studied over the wavelength range of 313-366 nm, by using monochromatic light. With the goal of understanding the unusual wavelength-dependent selectivity observed for 5-methyl-1,5-hexadien-3-one (1), quantum yield measurements, structure reactivity studies, triplet sensitization, and quenching experiments are performed. While six of the ten dienones studied show selectivities that are independent of irradiation wavelength from 313 to 366 nm, four of the dienones exhibit wavelength-dependent selectivities that are similar to that observed in 1, thus establishing that 1 is not unique, as previously believed. Triplet sensitization studies suggest that the wavelength dependence results, largely, from a single-state α-cleavage reaction that competes with triplet cycloaddition. A variety of triplet quenchers were ineffective at inhibiting these reactions. Some possible mechanisms are discussed.
The Influence of Intramolecular Dynamics on Branching Ratios in Thermal Rearrangements
Newmann-Evans, Richard H.,Simon, Reyna J.,Carpenter, B. K.
, p. 695 - 711 (2007/10/02)
1- and 2-phenylbicyclohex-2-enes-5-d undergo thermal rearrangement to give products, differing only in the location of the deuterium, in ratio of about 9:1, but with identical activation enthalphies.Similarly, opticallly active trans-2-methyl-1-(trans-2-phenylethenyl)cyclopropane is found to rearrange to enantiomeric methylphenylcyclopentenes that are formed in a 5.9:1 ratio but with virtually identicyl activation enthalphies.Barring repeated coincidence, these results do not seem to be explicable within the framework of statistical theories of unimolecular kinetics such as RRKM theory, transition state theory, and variational transition state theory.The possible influence of dynamic effects in these and other unimolecular reactions is discussed.
