- A Difluoroboron β-Diketonate Probe Shows turn-on Near-Infrared Fluorescence Specific for Tau Fibrils
-
Tau aggregation in neuronal cells has recently received significant attention as a robust predictor of the progression of Alzheimer's disease (AD) because of its proven correlation with the degree of cognitive impairment in AD patients. Accordingly, noninvasive imaging of tau aggregates has been highlighted as a promising diagnostic tool for AD. We have previously identified a tau-specific turn-on near-infrared fluorescent (NIRF) probe (1), and, in this study, structural modification was performed to optimize its physicochemical as well as fluorescence properties. Thus, a series of fluorescent dyes (2a-2j) composed of a variously substituted difluoroboron β-diketonate and an N,N-dimethylaniline moiety linked by a length-extendable π-bridge were prepared. Among those, isobutyl-substituted difluoroboron β-ketonate with a π-conjugated 1,4-butadienyl linker (2e) showed the most promising properties as a tau-specific NIRF probe. Compared with 1, the turn-on fluorescence of 2e was more specific to tau fibrils, and it showed 8.8- and 6.2-times higher tau-over-Aβ and tau-over-BSA specificity, respectively. Also, the fluorescence intensity of 2e upon binding to tau fibrils was substantially higher (～2.9 times) than that observed from 1. The mechanism for tau-specificity of 2e was investigated, which suggested that the molecular rotor-like property of 2e enables specific recognition of the microenvironment of tau aggregates to emit strong fluorescence. In transgenic cell lines stably expressing GFP-tagged tau proteins, 2e showed good colocalization with tau-GFP. Moreover, the fluorescence from 2e exhibited almost complete overlap with p-Tau antibody staining in the human AD brain tissue section. Collectively, these observations demonstrate the potential of 2e as a tau-specific fluorescent dye in both in vitro and ex vivo settings.
- Park, Kwang-Su,Kim, Mi Kyoung,Seo, Yujin,Ha, Taewoong,Yoo, Kyeongha,Hyeon, Seung Jae,Hwang, Yu Jin,Lee, Junghee,Ryu, Hoon,Choo, Hyunah,Chong, Youhoon
-
-
Read Online
- Method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and diphosphine ligand used in method
-
The invention discloses a method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and a diphosphine ligand used in the method. According to the invention, indole-substituted phosphoramidite diphosphine ligand which is stable in air and insensitive to light is synthesized by utilizing a continuous one-pot method, and the indole-substituted phosphoramidite diphosphine ligand and a rhodium catalyst are used for jointly catalyzing to successfully achieve a hydroformylation reaction of aromatic terminal alkyne and terminal conjugated eneyne under the condition of synthesis gas for the first time, so that an olefine aldehyde structure compound can be rapidly and massively prepared, and particularly, a polyolefine aldehyde structure compound which is more difficult to synthesize in the prior art can be easily prepared and synthesized, and a novel method is provided for synthesis and modification of drug molecules, intermediates and chemical products.
- -
-
Paragraph 0126-0132
(2021/05/29)
-
- Aromatic amines in organic synthesis. Part ii. p‐aminocinnamaldehydes
-
Ten derivatives of p‐aminocinnamic aldehydes were prepared from the reaction of either aromatic amines with dimethylaminoacrolein or benzaldehydes with acetaldehyde. Their chemical structure and purity were verified by1H NMR,13C NMR and IR spectroscopic methods. We found that the synthesis applying dimethylaminoacrolein as the reagent gets better yields than the one based on the reaction with acetaldehyde. The yields of the cinnamic aldehydes varied according to the type of the amino group and the number and position of the substituents. The basic spectroscopic properties of the p‐aminocinnamic aldehydes are also described since the compounds may be a precursor for the synthesis of dyes for diverse applications, e.g., in medicine and optoelectronics.
- J?drzejewska, Beata,Pietrzak, Marek
-
-
- Benzothiazolium Derivative-Capped Silica Nanocomposites for β-Amyloid ImagingIn Vivo
-
Alzheimer’s disease (AD) is a neurodegenerative disease, and β-amyloid (Aβ) is believed to be a causative factor in AD pathology. The abnormal deposition of Aβ is believed to be responsible for progression of AD. In order to facilitate the imaging of Aβin vivo, suitable probe molecules with a near-infrared emission wavelength that can penetrate the blood-brain barrier (BBB) were utilized. The commercial fluorescent probe thioflavin-T (ThT) is used to image Aβ; however, because of its short emission wavelength and poor BBB penetration, ThT can only be usedin vitro. With this research, based on ThT, we design three fluorescent probes (SZIs) having a longer emission wavelength in order to image Aβ aggregates. SZIs with different numbers of double bonds respond to Aβ aggregates. The SZIs have a structure similar to ThT, and as such, the SZIs are also unable to penetrate the BBB. To deal with the problem, we develop nanocomposites (MSN-Lf@SZIs) to deliver SZIs into the brain of AD mouse and image Aβ successfully. These new nanocomposites are able to deliver the dyes into the brain and facilitate Aβ imagingin vivo.
- Ma, Lijun,Yang, Shu,Ma, Yufan,Chen, Yuzhi,Wang, Zhenguo,James, Tony D.,Wang, Xuefei,Wang, Zhuo
-
p. 12617 - 12627
(2021/09/30)
-
- Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
-
The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo- and regioselectivity at low temperatures and low syngas pressures.
- Zhao, Jiangui,Zheng, Xueli,Tao, Shaokun,Zhu, Yuxin,Yi, Jiwei,Tang, Songbai,Li, Ruixiang,Chen, Hua,Fu, Haiyan,Yuan, Maolin
-
supporting information
p. 6067 - 6072
(2021/08/16)
-
- NOVEL COMPOUNDS USEFUL AS NEAR-INFRARED FLUORESCENT PROBES SELECTIVELY BINDING TO TAU AGGREGATES AND METHOD OF PREPARING THE SAME
-
Disclosed are a compound with near-infrared fluorescence that selectively binds to tau aggregates, a method for preparing the same, a tau-targeting near-infrared fluorescent probe including the compound, a composition for detecting a tau fiber protein containing the near-infrared fluorescent probe as an active ingredient, and the use of the composition for the diagnosis of tauopathy. In particular, the compound does not bind to an amyloid beta protein and has high selectivity to a tau aggregate, specifically reported as an etiology of the initial state of tauopathy, thus being useful as a near-infrared fluorescent detector for detecting a tau fiber protein for early diagnosis of a tauopathy including Alzheimer's disease.
- -
-
Paragraph 0184-0188
(2021/08/20)
-
- Heck Reactions of Acrolein or Enones and Aryl Bromides – Synthesis of 3-Aryl Propenals or Propenones and Consecutive Application in Multicomponent Pyrazole Syntheses
-
3-(Hetero)aryl propenals or propenones are efficiently prepared by a Heck reaction of (hetero)aryl bromides and acrolein or vinyl ketones using Beller's CataCXium Ptb ligand under Jeffery's and Fu's conditions. The formation of these three-carbon building blocks is embedded into consecutive three- and pseudo-four-component syntheses of 3-(hetero)aryl and 3,5-diarylpyrazoles with a broad substitution pattern in moderate to excellent yield.
- Stephan, Marvin,Panther, Jesco,Wilbert, Fabio,Ozog, Pauline,Müller, Thomas J. J.
-
supporting information
p. 2086 - 2092
(2020/03/23)
-
- Phosphorous acid promoted isomerization of propargyl alcohols to α,β-unsaturated carbonyl compounds
-
A metal-free and two-phase protocol for the Meyer-Schuster isomerization of propargyl alcohols to the corresponding α,β-unsaturated carbonyl compounds has been achieved in the presence of stoichiometric phosphorous acid aqueous solution, which produces the desired products in high yields with excellent stereoselectivity. Compared with the traditional methods, the procedure features broad scope of the substrates, mild conditions, and easy separation, providing an appealing alternative to the Meyer-Schuster reaction.
- Gan, Xiaotang,Fu, Zuqi,Liu,Yan, Yani,Chen, Chao,Zhou, Yongbo,Dong, Jianyu
-
-
- Synthesis, structure, linear and nonlinear properties of tricyanofuran–terminated merocyanine dyes
-
Structural and spectroscopic characteristics of merocyanine dyes are important because of their potential applications in optoelectronics and sensors. Herein we report synthesis, X-ray diffraction characterization of crystal structure, spectroscopic and NMR studies of four merocyanine dyes which, according to their strong donor-acceptor structure, exhibit a second order polarizability (β). Crystallographic studies demonstrated an almost planar structure of all molecules and indicated the occurrence of conformational changes in π-conjugated bridge between donor and acceptor. For three homologues similar packing modes, defined mostly by week C[sbnd]H?N interactions, were found in crystals. Bond length alternation (BLA) values have been evaluated using crystallographic and NMR data and have shown a correlation to their nonlinear optical activity. Second order polarizabilities for all compounds were measured using hyper Rayleigh scattering (HRS) in solution. It was found that the merocyanines studied exhibit very large second order polarizabilities (up to 4.1 10?27 esu), making them potentially useful for materials for second harmonic generation (SHG). Unfortunately, they do not demonstrate acentric packing of chromophores, which is required for SHG in the crystalline state, but may show promise for other applications such as poled polymer blends or for SHG sensing in biological environments.
- Tillotson, John P.,Bogdanov, Georgii,Jucov, Evgheni V.,Khrustalev, Victor N.,Rigin, Sergei,Hales, Joel M.,Perry, Joseph W.,Timofeeva, Tatiana V.
-
p. 146 - 154
(2019/04/26)
-
- Palladium-Catalyzed Formylation of Alkenylzinc Reagents with S-(4-Nitrophenyl) Thioformate
-
We report the synthesis of enal compounds by palladium-catalyzed formylation of alkenylzinc reagents with S-(4-nitrophenyl) thioformate. Various functional groups were tolerated in the present reaction. 1H NMR experiments revealed that the products had a non-protected formyl group, which can be utilized for further C–C bond formation reactions. We successfully achieved the one-pot synthesis of a 1,5-diene-3-ol compound via sequential formylation and allylation.
- Haraguchi, Ryosuke,Tanazawa, Sho-Go,Tokunaga, Naoya,Fukuzawa, Shin-Ichi
-
supporting information
p. 1761 - 1764
(2018/04/27)
-
- Novel green-yellow-orange-red light emitting donor-π-acceptor type dyes based on 1,3-indandione and dimedone moieties
-
Ten novel luminescent dyes containing 1,3-indandione or dimedone as electron acceptors, amino derivatives (dimethylamino, diphenylamino, julolidine and dibiphenylamino) as electron donor units and different length olefinic linkers (1-hydroxyallylidene or 1-hydroxypenta-2,4-dien-1-ylidene) are reported in this study. Newly synthesized compound structures are proven with X-ray analysis, 1H, 13C NMR spectroscopy and elemental analysis. The UV–Vis absorption, emission, solvatochromism, solvatofluorochromism, redox properties, as well as thermal stabilities and quantum chemical calculations of these dyes were systematically investigated to outline relation between structure and properties. These dyes exhibit moderate thermal decomposition temperatures above 200?°C, insignificant solvatochromism and positive, significant solvatofluorochromism, large Stokes shifts and green, yellow, orange and red light emission with quantum yields in range from 0.03 to 0.93 in non-polar solvents and in thin films. Quantum-chemical calculations (DFT) shows, that all dyes exhibit small HOMO/LUMO gaps from 2.77 to 3.22?eV, which is in agreement with experimental data.
- Malina, Ilze,Kampars, Valdis,Turovska, Baiba,Belyakov, Sergey
-
p. 820 - 830
(2017/01/21)
-
- Diarylpentadienone derivatives (curcumin analogues): Synthesis and anti-inflammatory activity
-
A series of new (2E,4E)-1-(substitutedphenyl)-5-(substitutedphenyl)penta-2,4-dien-1-one derivatives were designed and synthesized. Compounds 3i, 3k were determined by X-ray. All of the compounds have been screened for their anti-inflammatory activity characterized by evaluating their inhibition against LPS-induced IL-6 and TNF-α release in cell RAW 264.7 stimulated with LPS. Compound 3i showed the highest anti-inflammatory activity on decreasing IL-6 and TNF-α. The further study showed that title compound 3i inhibited expression of proteins p-p65, iNOS, COX-2 LPS-induced. Immunofluorescence also revealed compound 3i could lightly reduce activation p65 in nuclei. These results indicate that compound 3i anti-inflammatory role may partly due to its inhibitory effect on the NF-κB signaling pathway.
- Wang, Zhi Sen,Chen, Liu Zeng,Liu, Xin Hua,Chen, Fei Hu
-
p. 1803 - 1807
(2017/04/04)
-
- Bi (NO3)3·5H2O and cellulose mediated Cu-NPs - A highly efficient and novel catalytic system for aerobic oxidation of alcohols to carbonyls and synthesis of DFF from HMF
-
A highly efficient and versatile catalytic system for oxidation of primary and secondary aromatic alcohols to carbonyls has been developed. High efficiency, general synthetic applicability, broader functional group tolerance and versatility towards oxidation of both primary and secondary aromatic alcohols are the key features of this green and sustainable protocol. Selective oxidation of 5-hydroxymethyl furfural (HMF) to biofuel 2,5-diformylfuran (DFF) has been observed in excellent yields. Use of sustainable bio-polymer cellulose as a Cu-nanoparticle support makes the catalytic system environmentally benign.
- Baruah, Diganta,Hussain, Farhaz L.,Suri, Mrinaly,Saikia, Ujwal Pratim,Sengupta, Pinaki,Dutta, Dipak Kumar,Konwar, Dilip
-
-
- Development of a robust reagent for the two-carbon homologation of aldehydes to (E)-α,β-unsaturated aldehydes in water
-
Synthesis of a new pinacolacetal-phosphonium salt and its reaction with aldehydes to give homologated acetals and two-carbon homologated unsaturated aldehydes is presented. The chemistry takes place in water under mild conditions and the sequence can be performed in one-flask operation.
- Mcnulty, James,Zepeda-Velazquez, Carlos,McLeod, David
-
supporting information
p. 3146 - 3149
(2013/11/06)
-
- Probing the surface polarity of inorganic oxides using merocyanine-type dyes derived from barbituric acid
-
The solid state complexes, solvatochromic and acidochromic behaviour of four merocyanine-type dyes derived from barbituric and thiobarbituric acid and their use as solvatochromic probe molecules for coloured surfaces are described. The dyes were obtained
- Seifert, Susan,Seifert, Andreas,Brunklaus, Gunther,Hofmann, Katja,Rueffer, Tobias,Lang, Heinrich,Spange, Stefan
-
supporting information; scheme or table
p. 674 - 684
(2012/05/04)
-
- Red-fluorescent argininamide-type NPY Y1 receptor antagonists as pharmacological tools
-
Fluorescently labelled NPY Y1 receptor (Y1R) ligands were synthesized by connecting pyrylium and cyanine dyes with the argininamide-type Y1R antagonist core structure by linkers, covering a wide variety in length and chemical nature, attached to the guanidine group. The most promising fluorescent probes had Y1R affinities (radioligand binding) and antagonistic activities (calcium assay) in the one- to two-digit nanomolar range. These compounds turned out to be stable under assay conditions and to be appropriate for the detection of Y1Rs by confocal microscopy in live cells. To improve the signal-to-noise ratio by shifting the emission into the near infrared, a new benzothiazolium-type fluorescent cyanine dye (UR-DE99) was synthesized and attached to the parent antagonist via a carbamoyl linker yielding UR-MK131, a highly potent fluorescent Y1R probe, which was also successfully applied in flow cytometry.
- Keller, Max,Erdmann, Daniela,Pop, Nathalie,Pluym, Nikola,Teng, Shangjun,Bernhardt, Günther,Buschauer, Armin
-
scheme or table
p. 2859 - 2878
(2011/06/22)
-
- Acrolein diethyl acetal: A three-carbon homologating reagent for the synthesis of β-arylpropanoates and cinnamaldehydes by heck reaction catalyzed by a Kaiser oxime resin derived palladacycle
-
A polymer palladacycle derived from Kaiser oxime resin was used as a source of palladium(0) in the chemoselective Heck reaction of acrolein diethyl acetal with aryl halides under ligand-free conditions. The use of typical Heck conditions afforded 3-arylpropionic esters, and the process can be directed to the synthesis of cinnamaldehydes under Cacchi conditions. These processes take place with rather low loading of the catalyst, which can be recovered by simple filtration and reused for at least five runs without competitive dehalogenation. This is the first time that a supported palladium complex has been reused under Cacchi conditions. ICP-OES analyses of the Pd content of the crude products in both transformations indicated lower leaching for the esters than for the aldehydes in the range up to 0.08 ppm for the esters and 0.8 ppm for the aldehydes. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Alacid, Emilio,Najera, Carmen
-
experimental part
p. 3102 - 3106
(2009/04/11)
-
- An improved general method for palladium catalyzed alkenylations and alkynylations of aryl halides under microwave conditions
-
Palladium catalyzed facile method for alkenylation and alkynylation of arylhalides in good to excellent yield under microwave condition is reported.
- Togninelli, Andrea,Gevariya, Harsukh,Alongi, Maddalena,Botta, Maurizio
-
p. 4801 - 4803
(2008/02/05)
-
- Tuning the oxidation properties of vanadium(V) through ligand stoichiometry
-
Vanadium(V) (5 mol %) and hydroxamic acid ligand (45 mol %) were found to promote the selective tert-butyl hydroperoxide-mediated oxidation of allylic and propargylic alcohols to the corresponding aldehydes and ketones.
- Zeng, Wei,Ballard, T. Eric,Melander, Christian
-
p. 5923 - 5926
(2007/10/03)
-
- Chemoselective Heck arylation of acrolein diethyl acetal catalyzed by an oxime-derived palladacycle
-
A dimeric 4-hydroxyacetophenone oxime-derived palladacycle has been used as a very efficient precatalyst for the chemoselective arylation of acrolein diethyl acetal to give either cinnamaldehyde derivatives or 3-arylpropanoate esters by proper choice of the reaction conditions. The synthesis of cinnamaldehyde derivatives can be performed by Heck reaction of acrolein diethyl acetal with iodo-, bromo- or chloroarenes in N,N-dimethylacetamide (DMA) using K2CO3 as base at 120°C and tetra-n-butylammonium acetate (TBAA) and KCl as additives, followed by acid workup. In the case of 3-arylpropanoate esters the corresponding arylation of acrolein diethyl acetal with iodoarenes can be performed at 90°C in aqueous DMA using (dicylohexyl)methylamine as base, whereas for bromoarenes the reaction has to be performed at 120°C using tetra-n-butylammonium bromide (TBAB) as additive. Alternatively, this process can be performed under microwave irradiation. These couplings take place in good yields and with lower catalyst loading than with palladium(II) acetate as well as in shorter reaction times and with lower excess of acrolein diethyl acetal.
- Nájera, Carmen,Botella, Luis
-
p. 9688 - 9695
(2007/10/03)
-
- Condensation of p-dimethylaminocinnamaldehyde with aniline and substituted anilines in micellar media
-
Optimal conditions were found for the reactions of aniline and its hydroxy-, carboxy-, methyl-, and nitro-substituted derivatives with p-dimethylaminocinnamaldehyde in the presence of sodium dodecyl sulfate micelles in the pH range 1-6. A correlation was revealed between the optimal pH value pK a of aromatic amines. The reaction in the model system aniline-p-dimethylaminocinnamaldehyde-sodium dodecyl sulfate in micelles formed by anionic surfactants is accelerated more than 1000-fold due to increased concentration of the reactive species in sodium dodecyl sulfate micelles. 2005 Pleiades Publishing, Inc.
- Doronin,Chernova,Gusakova
-
p. 261 - 267
(2007/10/03)
-
- An efficient palladium-catalyzed synthesis of cinnamaldehydes from acrolein diethyl acetal and aryl iodides and bromides
-
(Matrix presented) The reaction of aryl iodides and bromides with acrolein diethyl acetal in the presence of Pd(OAc)2, nBu 4NOAc, K2CO3, KCl, and DMF, at 90°C until the disappearance of the acetal followed by the addition of 2 N HCl to the crude reaction mixture, affords cinnamaldehydes in good to high yields. A variety of functional groups are tolerated in the aryl halides, including ether, aldehyde, ketone, ester, dialkylamino, nitrile, and nitro groups. The presence of substituents close to the oxidative addition site does not hamper the reaction.
- Battistuzzi, Gianfranco,Cacchi, Sandro,Fabrizi, Giancarlo
-
p. 777 - 780
(2007/10/03)
-
- Computer aided benzothiazole derivatives. Synthesis, structure and biological study of new push-pull conjugated benzothiazolium salts
-
As the conjugation is assumed to enhance the biological activity of push-pull type benzothiazolium salts, new compounds with extended conjugated bridge between benzothiazolium and phenyl ring were designed and synthesized. The compounds have been tested against the model microorganism Euglena gracilis as well as 6 microorganisms including Gram-positive and Gram-negative bacteria , a yeast and a mould. In accordance with predictions, the prepared compounds showed enhanced activity against Euglena and Gram-positive bacteria and some of them also interesting fungicidal and fungistatic activity.
- Buffa,Zahradnik,Foltinova
-
p. 331 - 336
(2007/10/03)
-
- An efficient benchtop system for multigram-scale kinetic resolutions using aldolase antibodies
-
The preparative scale kinetic resolution of racemic aldols 1-4 using aldolase antibodies 38C2 (Aldrich no. 47995-0) and 84G3 (Aldrich no. 52785-8) is described. These reactions use a biphasic aqueous/organic solvent system that allows the catalyst to be reused. Reaction scales range from miligrams to grams, with 0.0086 to 0.12 mol% of antibody binding sites. Because antibodies 38C2 and 84G3 have opposite enantioselectivities, both aldol product enantiomers are accessible by kinetic resolution.
- Turner, James M.,Bui, Tommy,Lerner, Richard A.,Barbas III, Carlos F.,List, Benjamin
-
p. 2772 - 2774
(2007/10/03)
-
- Chemically reactive immunogens lead to functional convergence of the immune response
-
An aldolase antibody, 24H6, which was obtained from immunization with the large hapten 2, is shown to possess an active-site lysine residue with a perturbed pK(a) of 7.0. This antibody catalyzes both the aldol addition and the retrograde aldol fragmentation with a broad range of substrates that are structurally different from the hapten. This observation suggests that in reactive immunization with 1,3-diketones, the hapten structure governs the chemistry but not the overall organization of the active site. Hammett correlation studies of the 38C2- and 24H6-catalyzed aldol and retroaldol reactions revealed that although the two antibodies exhibit broad substrate specificities, they utilize slightly different mechanisms. While antibody 38C2 adopts a mechanism that is reminiscent of an acid-catalyzed aldol reaction, antibody 24H6 follows a mechanism that is similar to the base-catalyzed reaction.
- Shulman,Makarov,Ogawa,Romesberg,Keinan
-
p. 10743 - 10753
(2007/10/03)
-
- Synthesis and hydrolysis of [alkenyl(alkoxy)carbene]manganese complexes: Evidence for a transient allylic intermediate on the way to α,β-unsaturated aldehydes
-
A variety of alkenylcarbene complexes [Cp'(CO)2Mn= C(OEt)CH=CHR] (3) (Cp' = TiS-MeCsH4) was obtained in a straightforward manner upon aldol condensation of [Cp'(CO)2Mn=C(OEt)CH3] (1) with aromatic and α,β- unsaturated aldehydes RC(H)O (2). The reaction is totally stereoselective, giving (E)- or (all-E)-alkenylcarbenes only. The protonation of 3 at low temperature followed by reaction with water affords the α,β-unsaturated aldehyde complexes [Cp'(CO)2Mn(n2-RCH=CHCHO] (5), from which the aldehydes RC(H)=C(H)C(H)O (6) were displaced by acetonitrile. The intermediate aldehyde complexes are shown to result from the hydrolysis of a transient cationic π- allyl species [Cp'(CO)2Mn(n3-RCHCHC(OEt)H]+ ([4]+) formed upon protonation of 3.
- Mongin, Carole,Ortin, Yannick,Lugan, Noel,Mathieu, Rene
-
p. 739 - 742
(2007/10/03)
-
- Crown-containing butadienyl dyes 1. synthesis, structure, fluorescence, and complex formation of chromogenic aza-15-crown-5 ethers
-
Crown-containing butadienyl dyes containing various heterocyclic moieties and azacrown ether fragments were synthesized for the first time. The spatial structures and the absorption and fluorescence spectra of crown-containing butadienyl dyes and their complexes with metal cations were examined. The effects of the nature of the heterocyclic and crown ether fragments on fluorescence and generation of dyes and their complexes with metal cations were revealed based on the spectral data.
- Gromov,Sergeev,Druzhinin,Rusalov,Uzhinov,Kuz'mina,Churakov,Howard,Alfimov
-
p. 525 - 536
(2007/10/03)
-
- Substrate-selective mechanisms in biocatalysis demonstrated with a versatile and efficient aldolase antibody
-
A structure-activity relationship study with a series of aldol substrates shows that the mechanism of the antibody 38C2-catalyzed retrograde aldol reaction depends on the nature of the substrate with electron-deficient substrates an early deprotonation precedes the C-C bond cleavage while with electron-rich substrates the catalytic mechanism involves an initial C-C bond cleavage leading to a positively charged intermediate.
- Shulman, Hagit,Keinan, Ehud
-
p. 1745 - 1750
(2007/10/03)
-
- Antibacterials and antimycotics: Part 1: Synthesis and activity of 2- pyrazoline derivatives
-
A series of 3-styryl-1,5-diphenyl and 5-styryl-1,3-diphenyl 2- pyrazolines of different substitutions has been synthesized by condensation of substituted α,β-unsaturated ketones with phenylhydrazine hydrochloride in presence of catalytic amount of concentrated HCl. Compounds in the 3- styryl series had OMe, NMe2, NO2, OH and isopropyl substituents and those in the 5-styryl series had OMe, NMe2 and NO(s). The 3-styryl-1,5-diphenyl compounds showed little variation in antibacterial activity towards gram- positive and gram-negative bacteria in terms of geometric mean minimum inhibitory concentrations (MIC). The 4',4-NMe2, 4',4-NO2 and 4',4-OMe compounds were found to possess the highest activity in the series. The 5- styryl-1,3-diphenyl series showed lower activities than the 3-styryl series. The in vitro antimycotic activity of the 4',4-OH and 2',2-OH substituted compounds showed good activity than the other molecules in the two series.
- Nauduri, Dhananjaya,Reddy, Gopu Bala Show
-
p. 1254 - 1260
(2007/10/03)
-
- A convenient synthetic entry into aldehydes with extended conjugation
-
Variable-length donor-acceptor polyenes 1-18 were synthesized. In the key step, a polyenal was appended to an aromatic donor through nucleophilic attack of an organolithium reagent on a vinylogous amide. Yields of aldehydes and dialdehydes in the one-pot process ranged from 12-64% and depended upon number of repeat units (n=1-3) in the polyene chain.
- Friedli, Andrienne C.,Yang, Edward,Marder, Seth R.
-
p. 2717 - 2730
(2007/10/03)
-
- A Simple and Highly Stereoselective Route to E-α,β-Unsaturated Aldehydes
-
Zinc bromide mediated reaction of α,α-bis(trimethylsilyl)-tert-butylacetaldimine (3) with a wide range of aldehydes takes place under mild conditions and affords the corresponding α,β-unsaturated aldehydes in good yields and with high E stereoselectivity (>98percent).This procedure is successfully applied to the preparation of intermediates for retinoid and natural product synthesis.
- Bellassoued, Moncef,Majidi, Assieh
-
p. 2517 - 2522
(2007/10/02)
-
- General-Acid-Catalyzed Imidazolidine Ring Opening. Hydrolysis of Symmetrical and Unsymmetrical 1,3-Imidazolidines of p-Dimethylaminocinnamaldehyde
-
Rate constants have been obtained for ring opening of a series of symmetrical and unsymmetrical 1,3-imidazolidines of p-dimethylaminocinnamaldehyde in H2O at 30 deg C.Ring opening of the N,N'-diphenyl derivative is catalyzed by hydronium ion (kH = 2290 M-1 s-1), and gives rise to a cationic Schiff base with λmax 505 nm.The reaction is considerably slower in D2O than in H2O, kH/kD = 3.0.At pH greater than 6 ring opening is pH independent (k0' = 1.8 10-2 s-1).Ring opening of the N,N'-dimethylimidazolidine to a species with λmax 480 nm is hydronium ion catalyzed (kH = 2 109 M-1 s-1) and pH independent at pH values above 11.5.The unsymmetrical N-isopropyl-N'-phenyl derivative opens to give a species with λmax 480 nm and with rate constants that are similar to those for the N,N'-dimethyl substituted compound (kH = 4 107 M-1 s-1).Consequently, this species must be the N-isopropyl Schiff base resulting from breaking of the C-N phenyl bond.General acid catalysis of ring opening was observed in trimethylamine buffer.Only at pH values less than 6 does C-N isopropyl bond breaking become competitive, giving the N-phenyl Schiff base (λmax 512 nm).The interconversion of Schiff bases (480 -> 512 nm) is general acid catalyzed by buffer acids or a kinetic equivalent.Thus, ring-opening reactions of imidazolidines have been directly monitored, and general acid catalysis has been observed.It can be concluded that, in reactions of the neutral species and hydronium ion, or a general acid, the imidazolidine ring opens preferentially to give the most stable carbonium ion with expulsion of the least basic nitrogen.In the reaction of the unsymmetrical imidazolidine at low pH when there are two protons in the transition state, either C-N bond may break, and the C-N phenyl Schiff base is the favored product.These results are discussed in relation to reactions of N5,N10-methylenetetrahydrofolic acid.
- Fife, Thomas H.,Pellino, August M.
-
p. 3062 - 3071
(2007/10/02)
-
- General-Acid-Catalyzed Ring Opening of Oxazolidines. Hydrolysis of 2--N-phenyl-1,3-oxazolidine
-
A cationic Schiff-base intermediate is detectable at pH -N-phenyl-1,3-oxazolidine.Thus, ring opening proceeds with C-O bond breaking, i.e., in the direction which gives the most stable carbonium ion intermediate.Ring opening is hydronium ion catalyzed at low pH and only slightly affected by the protonation state of the p-dimethylamino group.From pH 5 to pH 7.5 ring opening occurs in a pH-independent reaction which probably involves unimolecular C-O bond breaking.At higher pH apparent hydroxide ion catalysis is observed in the reversible ring opening, which reflects reclosure of the ring by attack of the neighboring alkoxide ion on the iminium ion.The value of pKeq for ring opening determined both spectroscopically and from the kinetic data is 8.05.General-acid catalysis occurs in ring opening.Proton transfer and C-O bond breaking are concerted, as shown by the Broensted coefficient α of 0.53.Concerted general-acid catalysis in these reactions is due to ease of C-O bond breaking brought about by stabilization of the developing carbonium ion in the transition state.The hydrolysis of the intermediate cationic Schiff base is pH independent in the pH range 8-13 and hydronium ion catalyzed at low pH due to protonation of the p-dimethylamino group.
- Fife, Thomas H.,Hutchins, J. E. C.
-
p. 2099 - 2104
(2007/10/02)
-
- Mechanism and equilibrium constants of the reaction between η4-heterodieneiron tricarbonyl complexes and group 5 ligands
-
The complexes Fe(CO)3(η2-C6H4XCH=CHCHO)L (where L = CO, X = 4-NMe2, 4-OMe, 3-OMe, 4-Me, 4-Cl; L = SbPh3, X = 3-OMe, 4-Cl) and Fe(CO)2(η4-C6H4XCH=CHCHO)L (where L = CO, X = 4-NMe2, 4-OMe, 3-OMe, 4-Me, 4-Cl; L = PPh3, X = H, 4-Cl, 4-Me, 4-OMe, 3-OMe) have been prepared and characterized. The reaction between Fe(CO)3(η4-C6H4XCH=CHCHO) (where X = H, 3-OMe, 4-Cl) and SbPh3 has been studied and the equilibrium constants and forward and reverse rate constants for this reaction have been measured. From the results obtained, it is concluded that the mechanism of this reaction proceeds via a dissociative equilibrium of the η4 complexes to η4 unsaturated complexes. The reaction between Fe(CO)3(η4-C6H4XCH=CHCHO) (where X = H, 4-NMe, 3-OMe, 4-OMe, 4-Me, 4-Cl) and PPh3 has also been studied. The kinetic law, the activation parameters, and the substituent effect indicate a reaction mode proceeding in two parallel directions. One of these is the same as that found for SbPh3 and the other corresponds to an associative process with the phosphine ligand. These results may be generalized to other diene complexes of iron tricarbonyl.
- Cardaci,Bellachioma
-
p. 3099 - 3104
(2007/10/12)
-
