cas 5221-44-3, N1-(4-PYRIDYL)BENZAMIDE | Articles data

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Synthesis, Characterization, and Catalytic Activity of Heteroleptic Rhodium Complex for C–N Couplings
Abstract: We have reported synthesis of complex [Rh(COD)(L{Me})Cl] (III), where L{Me} (II) is N-(1-methylpyridin-4(1H)-ylidene)benzamide and COD is 1,5-cyclooctadiene. Monodentate ligand L{Me} was synthesized by deprotonation of [HL{Me}][OTf] (I) with sodium hydride. [HL{Me}][OTf] was synthesised by methylation of N-(pyridin-4-yl)benzamide (HL) with methyl triflate. All the three synthesized compounds were characterized by FT-IR, NMR (1H and 13C), elemental and MS analyses. The structure of complex I was further explored with single crystal XRD and computational studies. Complex I was found as a good catalyst for C–N coupling reactions. Molecular docking revealed strong binding of rhodium complex with myoglobin.
Zafar,Perveen, Fouzia,Naz,Mughal, Ehsan Ullah,Gul-e-Saba,Hina
p. 62 - 73
(2019)
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N-Ammonium Ylide Mediators for Electrochemical C-H Oxidation
The site-specific oxidation of strong C(sp3)-H bonds is of uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification of lead compounds to truncating retrosynthetic plans, there is a growing need for new reagents and methods for achieving such a transformation in both academic and industrial circles. One main drawback of current chemical reagents is the lack of diversity with regard to structure and reactivity that prevents a combinatorial approach for rapid screening to be employed. In that regard, directed evolution still holds the greatest promise for achieving complex C-H oxidations in a variety of complex settings. Herein we present a rationally designed platform that provides a step toward this challenge using N-ammonium ylides as electrochemically driven oxidants for site-specific, chemoselective C(sp3)-H oxidation. By taking a first-principles approach guided by computation, these new mediators were identified and rapidly expanded into a library using ubiquitous building blocks and trivial synthesis techniques. The ylide-based approach to C-H oxidation exhibits tunable selectivity that is often exclusive to this class of oxidants and can be applied to real-world problems in the agricultural and pharmaceutical sectors.
Saito, Masato,Kawamata, Yu,Meanwell, Michael,Navratil, Rafael,Chiodi, Debora,Carlson, Ethan,Hu, Pengfei,Chen, Longrui,Udyavara, Sagar,Kingston, Cian,Tanwar, Mayank,Tyagi, Sameer,McKillican, Bruce P.,Gichinga, Moses G.,Schmidt, Michael A.,Eastgate, Martin D.,Lamberto, Massimiliano,He, Chi,Tang, Tianhua,Malapit, Christian A.,Sigman, Matthew S.,Minteer, Shelley D.,Neurock, Matthew,Baran, Phil S.
supporting information
p. 7859 - 7867
(2021/05/26)

A practical and sustainable protocol for direct amidation of unactivated esters under transition-metal-free and solvent-free conditions
In this paper, a NaOtBu-mediated synthesis approach was developed for direct amidation of unactivated esters with amines under transition-metal-free and solvent-free conditions, affording a series of amides in good to excellent yields at room temperature. In particular, an environmentally friendly and practical workup procedure, which circumvents the use of organic solvents and chromatography in most cases, was disclosed. Moreover, the gram-scale production of representative products3a,3wand3auwas efficiently realized by applying operationally simple, sustainable and practical procedures. Furthermore, this approach was also applicable to the synthesis of valuable molecules such as moclobemide (a powerful antidepressant), benodanil and fenfuram (two commercial agricultural fungicides). These results demonstrate that this protocol has the potential to streamline amide synthesis in industry. Meanwhile, quantitative green metrics of all the target products were evaluated, implying that the present protocol is advantageous over the reported ones in terms of environmental friendliness and sustainability. Finally, additional experiments and computational calculations were carried out to elucidate the mechanistic insight of this transformation, and one plausible mechanism was provided on the basis of these results and the related literature reports.
Chen, Cheng,Cheng, Hua,Du, Min-Chen,Qian, Liang,Qin, Xin,Sang, Wei,Yao, Wei-Zhong,Yuan, Ye,Zhang, Rui
supporting information
p. 3972 - 3982
(2021/06/17)

Manganese Catalyzed Direct Amidation of Esters with Amines
The transition metal catalyzed amide bond forming reaction of esters with amines has been developed as an advanced approach for overcoming the shortcomings of traditional methods. The broad scope of substrates in transition metal catalyzed amidations remains a challenge. Here, a manganese(I)-catalyzed method for the direct synthesis of amides from a various number of esters and amines is reported with unprecedented substrate scope using a low catalyst loading. A wide range of aromatic, aliphatic, and heterocyclic esters, even in fatty acid esters, reacted with a diverse range of primary aryl amines, primary alkyl amines, and secondary alkyl amines to form amides. It is noteworthy that this approach provides the first example of the transition metal catalyzed amide bond forming reaction from fatty acid esters and amines. The acid-base mechanism for the manganese(I)-catalyzed direct amidation of esters with amines was elucidated by DFT calculations.
Fu, Zhengqiang,Wang, Xinghua,Tao, Sheng,Bu, Qingqing,Wei, Donghui,Liu, Ning
p. 2339 - 2358
(2021/02/03)

Discovery of methoxy-naphthyl linked N-(1-benzylpiperidine) benzamide as a blood-brain permeable dual inhibitor of acetylcholinesterase and butyrylcholinesterase
The cholinesterase enzymes play a vital role in maintaining balanced levels of the neurotransmitter acetylcholine in the central nervous system. However, the overexpression of these enzymes results in hampered neurotransmission. Both the major forms of cholinesterase enzymes viz. acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) play a crucial role in blocking neurotransmission; therefore, in recent years, a strategy of dual cholinesterase inhibition is being explored. Herein, we developed an energy-optimized e-pharmacophore hypothesis AHHPRR from AChE-donepezil complex and screened a set of 15 scaffolds that were designed imaginarily. The ligand with N-(1-benzylpyridinium) benzamide framework has shown the highest fitness and volume score, which was chosen for synthesis and validation. A series of pyridinium benzamides were synthesized and screened for cholinesterase inhibition that led to the identification of 7b, a naphthalene containing N-(1-benzylpiperidine) benzamide as a potent dual AChE and BChE inhibitor with IC50 values of 0.176, and 0.47 μM, respectively. The kinetic study indicated that 7b inhibits AChE in a non-competitive manner with Ki value of 0.21 μM, and BChE in a mixed-fashion with Ki of 0.15 μM. The observed mode of inhibition was corroborated with molecular docking studies. The MD simulation studies pointed out that both AChE and BChE undergo low conformational changes in complex with 7b. The benzamide 7b displayed high BBB permeability in PAMPA assay, which indicates its potential for further exploration in preclinical studies for Alzheimer's disease.
Abdullaha, Mohd,Bharate, Sandip B.,Nuthakki, Vijay K.
(2020/09/18)

Donor Strength Determination of Pyridinylidene-amide Ligands using Their Palladium-NHC Complexes
Pyridinylidene-amides (PYAs) are a relatively new type of N-donor ligands that can exist in three isomeric forms and adopt various resonance structures. This makes them electronically flexible, and in order to evaluate their electronic profile using the Huynh electronic parameter (HEP), seven structurally diverse mixed N-heterocyclic carbenes (NHCs)/PYA palladium complexes of the type trans-[PdBr2(iPr2-bimy)(PYA)] were prepared and fully characterized by various spectroscopic and spectrometric methods. This study shows that PYAs are among the strongest, formally neutral N-donors, but they are still weaker than phosphines and organometallic ligands such as NHCs. Notably, the donating abilities of isomeric PYAs are distinct and can be further fine-tuned by the choice of two substituents making them structurally and electronically versatile. These characteristics and the ease of their preparation hold promise for a wide applicability in coordination chemistry.
Huynh, Han Vinh,Vossen, Jeroen Thomas
supporting information
p. 12486 - 12493
(2020/09/02)

Iodine-mediated aryl transfer reaction from arylhydrazine hydrochlorides to nitriles
An iodine-promoted, metal-, base-, and solvent-free cross-coupling reaction was developed for the synthesis of various useful secondary amides via an aryl N-addition reaction of aryl groups to cyano groups. This aryl transfer reaction proceeds with arylhydrazine hydrochlorides serving as the aryl donors. A labelling experiment shows that the N atom in the product comes from the cyano group of the nitriles, which are low in cost. A plausible radical-driven mechanism is also proposed.
Zhang, Zhiguo,Li, Xiang,Li, Yinghua,Guo, Yan,Zhao, Xunan,Yan, Yan,Sun, Kai,Zhang, Guisheng
supporting information
p. 3628 - 3635
(2019/05/29)

Solvent- and transition metal-free amide synthesis from phenyl esters and aryl amines
A general, economical, and environmentally friendly method of amide synthesis from phenyl esters and aryl amines was developed. This new method has significant advantages compared to previously reported palladium-catalyzed approaches. The reaction is performed transition metal- and solvent-free, using a cheap and environmentally benign base, NaH. This approach enabled us to obtain target amides in high yields with high atom economy.
Rzhevskiy, Sergey A.,Ageshina, Alexandra A.,Chesnokov, Gleb A.,Gribanov, Pavel S.,Topchiy, Maxim A.,Nechaev, Mikhail S.,Asachenko, Andrey F.
p. 1536 - 1540
(2019/01/24)

A Cross-Coupling Approach to Amide Bond Formation from Esters
A palladium-catalyzed cross-coupling between aryl esters and anilines is reported, enabling access to diverse amides. The reaction takes place via activation of the C-O bond by oxidative addition with a Pd-NHC complex, which enables the use of relatively non-nucleophilic anilines that otherwise require stoichiometric activation with strong bases in order to react. High yields of aromatic, aliphatic, and heterocyclic products are obtained. A range of activated esters are evaluated in the presence and absence of catalyst, demonstrating that the catalytic methodology substantially increases the types of electrophiles that can be utilized for amide bond formation in the absence of harsh bases.
Ben Halima, Taoufik,Vandavasi, Jaya Kishore,Shkoor, Mohanad,Newman, Stephen G.
p. 2176 - 2180
(2017/08/09)

Efficient and Mild Ullmann-Type N-Arylation of Amides, Carbamates, and Azoles in Water
A simple, sustainable, efficient, mild, and low-cost protocol was developed for d-glucose-assisted Cu-catalyzed Ullmann reactions in water for amides, carbamates, and nitrogen-containing heterocycles. The reaction was compatible with diverse aryl/heteroaryl iodides, giving highly substituted pyridine, indole, or indazole rings. This method offers an attractive alternative to existing protocols, because the reaction proceeds in aqueous media, occurs at or near ambient temperature, and provides the N-arylated products in good to high yields.
Bollenbach, Maud,Aquino, Pedro G. V.,de Araújo-Júnior, Jo?o Xavier,Bourguignon, Jean-Jacques,Bihel, Frédéric,Salomé, Christophe,Wagner, Patrick,Schmitt, Martine
supporting information
p. 13676 - 13683
(2017/10/10)

Vanadium-Catalyzed Oxidative C(CO)-C(CO) Bond Cleavage for C-N Bond Formation: One-Pot Domino Transformation of 1,2-Diketones and Amidines into Imides and Amides
A novel vanadium-catalyzed one-pot domino reaction of 1,2-diketones with amidines has been identified that enables their transformation into imides and amides. The reaction proceeds by dual acylation of amidines via oxidative C(CO)-C(CO) bond cleavage of 1,2-diketones to afford N,N′-diaroyl-N-arylbenzamidine intermediates. In the reaction, these intermediates are easily hydrolyzed into imides and amides through vanadium catalysis. This method provides a practical, simple, and mild synthetic approach to access a variety of imides as well as amides in high yields. Moreover, one-step construction of imide and amide bonds with a long-chain alkyl group is an attractive feature of this protocol.
Digwal, Chander Singh,Yadav, Upasana,Ramya, P. V. Sri,Sana, Sravani,Swain, Baijayantimala,Kamal, Ahmed
p. 7332 - 7345
(2017/07/26)

Donor-Flexible Nitrogen Ligands for Efficient Iridium-Catalyzed Water Oxidation Catalysis
A pyridylideneamide ligand with variable donor properties owing to a pronounced zwitterionic and a neutral diene-type resonance structure was used as a dynamic ligand at a Cp? iridium center to facilitate water oxidation catalysis, a reaction that requires the stabilization of a variety of different iridium oxidation states and that is key for developing an efficient solar fuel device. The ligand imparts high activity (nearly three-fold increase of turnover frequency compared to benchmark systems), and exceptionally high turnover numbers, which indicate a robust catalytic cycle and little catalyst degradation.
Navarro, Miquel,Li, Mo,Müller-Bunz, Helge,Bernhard, Stefan,Albrecht, Martin
supporting information
p. 6740 - 6745
(2016/05/11)

Metal-free oxidative amidation of aldehydes with aminopyridines employing aqueous hydrogen peroxide
The first metal free report on the amidation of aldehydes with aminopyridines was accomplished using simple aqueous hydrogen peroxide (aq. H2O2) as the oxidant. No catalysts or additives were needed for this transformation and the reaction proceeded in water, an environmentally benign reaction medium. Green oxidant and reaction conditions, and the ability to construct diverse N-(pyridin-2-yl)benzamide by this elegant method render it a practical alternative for the synthesis of these amides.
Sankari Devi,Alanthadka, Anitha,Tamilselvi,Nagarajan, Subbiah,Sridharan, Vellaisamy,Maheswari, C. Uma
supporting information
p. 8228 - 8231
(2016/09/09)

Efficient conversion of acids and esters to amides and transamidation of primary amides using OSU-6
OSU-6, an MCM-41 type hexagonal mesoporous silica with strong Bronsted acid properties, has been used to promote the high-yield conversion of carboxylic acids and esters to carboxamides as well as transamidations of primary amides in a one-pot solventless approach. A metal-free heterogeneous catalyst that promotes all of these processes has not been previously reported. OSU-6 enables these transformations to proceed in shorter times and at lower temperatures for a broad range of substrates. An added benefit is that the catalyst can be recycled and reused multiple times without significant loss of activity.
Nammalwar, Baskar,Muddala, Nagendra Prasad,Watts, Field M.,Bunce, Richard A.
p. 9101 - 9111
(2015/11/09)

Practical preparation of challenging amides from non-nucleophilic amines and esters under flow conditions
A fast and efficient protocol for the formation of amides from low nucleophilic amines and esters in flow is described. Products were obtained in good to excellent yields and with the advantage of simultaneous mixing of all reagents at once, avoiding steps for intermediate formation. The protocol is also suitable to be combined with ester synthesis, resulting in the preparation of amides in-line from haloarenes. This journal is
Vrijdag, Johannes L.,Delgado, Francisca,Alonso, Nerea,De Borggraeve, Wim M.,Prez-Macias, Natalia,Alczar, Jesus
supporting information
p. 15094 - 15097
(2014/12/11)

Lead identification of novel and selective TYK2 inhibitors
A therapeutic rationale is proposed for the treatment of inflammatory diseases, such as psoriasis and inflammatory bowel diseases (IBD), by selective targeting of TYK2. Hit triage, following a high-throughput screen for TYK2 inhibitors, revealed pyridine 1 as a promising starting point for lead identification. Initial expansion of 3 separate regions of the molecule led to eventual identification of cyclopropyl amide 46, a potent lead analog with good kinase selectivity, physicochemical properties, and pharmacokinetic profile. Analysis of the binding modes of the series in TYK2 and JAK2 crystal structures revealed key interactions leading to good TYK2 potency and design options for future optimization of selectivity.
Liang, Jun,Tsui, Vickie,Van Abbema, Anne,Bao, Liang,Barrett, Kathy,Beresini, Maureen,Berezhkovskiy, Leo,Blair, Wade S.,Chang, Christine,Driscoll, James,Eigenbrot, Charles,Ghilardi, Nico,Gibbons, Paul,Halladay, Jason,Johnson, Adam,Bir Kohli, Pawan,Lai, Yingjie,Liimatta, Marya,Mantik, Priscilla,Menghrajani, Kapil,Murray, Jeremy,Sambrone, Amy,Xiao, Yisong,Shia, Steven,Shin, Young,Smith, Jan,Sohn, Sue,Stanley, Mark,Ultsch, Mark,Zhang, Birong,Wu, Lawren C.,Magnuson, Steven
p. 175 - 187
(2013/10/01)

Use of molecular oxygen as a reoxidant in the synthesis of 2-substituted benzothiazoles via palladium-catalyzed C-H functionalization/intramolecular C-S bond formation
Molecular oxygen (O2) was successfully employed as a reoxidant in cyclizations of thiobenzanilides 1a-s through a palladium-catalyzed C-H functionalization/intramolecular C-S bond formation process, leading to an efficient, green method for the synthesis of 2-arylbenzothiazoles 2a-s. Addition of cesium fluoride (CsF) greatly enhanced the reactions, which produced variously substituted 2-arylbenzothiazoles with good functional group tolerance. Thioureas 4a-j were also found to be suitable substrates for the cyclization process using a palladium/O2 catalyst system, thus generating 2-aminobenzothiazoles 5a-j. One-pot syntheses of 2-aminobenzothiazoles 5a-j from aryl isothiocyanates 6 and amines 7 were also successful.
Inamoto, Kiyofumi,Hasegawa, Chisa,Kawasaki, Junpei,Hiroya, Kou,Doi, Takayuki
experimental part
p. 2643 - 2655
(2010/12/25)

N,N-carbonyldiimidazole-mediated amide coupling: Significant rate enhancement achieved by acid catalysis with imidazole - HCI
Over a series of 10 aromatic amines we show the rate of CDI mediated amidation to be significantly enhanced upon introduction of imidazole·HCI as a proton source for acid catalysis. Our work supports and provides an application for previous investigations into the imidazolium effect, thus increasing the scope of CDI as an amide-coupling reagent with aromatic amines. The influence of the relative pKa of the amines studied on the rate of reaction was also investigated.
Woodman, Emily K.,Chaffey, Julian G. K.,Hopes, Philip A.,Hose, David R. J.,Gilday, John P.
supporting information; experimental part
p. 106 - 113
(2010/04/22)

Microwave-assisted synthesis of amides from various amines and benzoyl chloride under solvent-free conditions: A rapid and efficient method for selective protection of diverse amines
A number of structurally diverse amides were synthesized by reaction of the corresponding amines with benzoyl chloride under microwave irradiation. The proposed procedure ensures short reaction time, high yields, and excellent selectivity and considerably broadens the series of amines as compared to the microwave-assisted synthesis of amides directly from carboxylic acids. It can also be used for selective protection of various amines, including aromatic, aliphatic, and heterocyclic.
Li, Yanqiu,Wang, Yulu,Wang, Jinye
p. 358 - 361
(2008/12/22)

Highly reactive, general and long-lived catalysts for palladium-catalyzed amination of heteroaryl and aryl chlorides, bromides, and iodides: Scope and structure-activity relationships
We describe a systematic study of the scope and relationship between ligand structure and activity for a highly efficient and selective class of catalysts containing sterically hindered chelating alkylphosphines for the amination of heteroaryl and aryl chlorides, bromides, and iodides. In the presence of this catalyst, aryl and heteroaryl chlorides, bromides, and iodides react with many primary amines in high yields with part-per-million quantities of palladium precursor and ligand. Many reactions of primary amines with both heteroaryl and aryl chlorides, bromides, and iodides occur to completion with 0.0005-0.05 mol % catalyst. A comparison of the reactivity of this catalyst for the coupling of primary amines at these loadings is made with catalysts generated from hindered monophosphines and carbenes, and these data illustrate the benefits of chelation. Studies on structural variants of the most active catalyst indicate that a rigid backbone in the bidentate structure, strong electron donation, and severe hindrance all contribute to its high reactivity. Thus, these complexes constitute a fourth-generation catalyst for the amination of aryl halides, whose activity complements catalysts based on monophosphines and carbenes.
Shen, Qilong,Ogata, Tokutaro,Hartwig, John F.
p. 6586 - 6596
(2008/12/22)

Microwave-promoted conversion of heterocyclic amines to corresponding amides under solvent-free conditions
An array of heterocyclic amides was synthesized efficiently by combining corresponding amines and benzoyl chloride in one-pot under microwave irradiation. The reaction times were shorter, yields were higher. What is more, the regioselectivity was excellent, which made the protocol support us an entry to selective protection of diverse amino groups.
Li, Yanqiu,Wang, Yulu,Wang, Jinye
p. 251 - 256
(2008/03/14)

Aminolysis of allyl esters with bislithium aryl amides
The aminolysis of allyl esters with bislithium amides is reported. Tertiary aryl amides were synthesized in a one-pot reaction with bislithium amides and a suitable electrophile in good yields. The scope of this reaction was demonstrated with a variety of anilines and aminopyridines and applied to the synthesis of triphenylmethylacetamides.
Faler, Catherine A.,Joullié, Madeleine M.
p. 7229 - 7231
(2007/10/03)

Highly reactive, general, and long-lived catalysts for coupling heteroaryl and aryl chlorides with primary nitrogen nucleophiles
Resisting pathways for decomposition followed by palladium complexes of monodentate ligands is one characteristic of the highly reactive but long-lived catalyst generated from the Josiphos ligand L and palladium. It catalyzes under mild conditions the coupling of primary amines with chloropyridines and chloroarenes in high yield with low catalyst loadings (see scheme).
Shen, Qilong,Shekhar, Shashank,Stambuli, James P.,Hartwig, John F.
p. 1371 - 1375
(2007/10/03)

Behaviour of N-pyridylbenzamides versus benzanilides in the ortho-directed lithiation of masked aromatic carboxylic acids
The reaction of N-pyridylbenzamides 1-3 with n-butyllithium or sec-butyllithium has been examined. The perfect selectivity that has been observed until now in the lithiation of anilides, a reaction used for ortho-functionalisation of masked aromatic carboxylic acids, has been broken; our results indicate that the pyridine ring at the position ortho to the directed metallation group is more susceptible to lithiation than the homoaromatic ring itself. This was proved in an intermolecular comparative study of benz-, picolin- and isonicotinanilides 14-16, and N-cumylbenzamide (17). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Jozwiak, Andrzej,Brzezinski, Jacek Z.,Plotka, Mieczyslaw W.,Szczesniak, Aleksandra K.,Malinowski, Zbigniew,Epsztajn, Jan
p. 3254 - 3261
(2007/10/03)

Photoreaction of 2-halo-N-pyridinylbenzamide: Intramolecular cyclization mechanism of phenyl radical assisted with n-complexation of chlorine radical
The photochemical behavior of 2-halo-N-pyridinylbenzamide (1-4 in Chart 1) was studied. The photoreaction of 2-chloro-N-pyridinylbenzamides 1a, 2a, 3a, and 4 afforded photocyclized products, benzo[c]naphthyridinones (6-9 and 16), in high yield, whereas the bromo analogues 1b, 2b, and 3b produced extensively photoreduced products, N-pyridinylbenzamides (1c, 10, and 11), with minor photocyclized product. Since the photocyclization reaction of 2-chloro-N-pyridinylbenzamide is retarded by the presence of oxygen and sensitized by the presence of a triplet sensitizer, acetone or acetophenone, a triplet state of the chloro analogue is involved in the reaction. Since several radical intermediates, particularly n-complexes of chlorine radical, are identified in the laser flash photolysis of 2-chloro-N-pyridinylbenzamide, an intramolecular cyclization mechanism of phenyl radical assisted with n-complexation of chlorine radical for the cyclization reaction is proposed: the triplet state (78 kcal/mol) of the chloro analogue (1a), which is populated by the excitation of 1a undergoes a homolytic cleavage of the C-Cl bond to give phenyl and chlorine radicals; while chlorine radical holds the neighbor pyridinyl ring with its n-complexation, the intramolecular arylation of the phenyl radical with the pyridinyl ring proceeds to produce a conjugated 2,3-dihydropyridinyl radical and then the conjugated radical aromatizes to afford a cyclized product, benzo[c]naphthyridinone by ejecting a hydrogen. The photoreduction product can be formed by hydrogen atom abstraction of the phenyl a radical from the environment.
Park,Jung,Kim,Kim,Song,Kim
p. 2197 - 2206
(2007/10/03)

Synthesis of 3,4-diaminopyridine and imidazo[4,5-c]pyridines by nitration of 4-acylaminopyridines
New methods for the preparation of 3,4-diaminopyridine (5) and imidazo[4,5-c]pyridines 7a,7b based on direct nitration of 4- acylaminopyridines 3a, 3b have been explored.
Bakke,Riha
p. 1143 - 1145
(2007/10/03)

Cation-controlled photophysics in a Re(I) fluoroionophore
Alkali and alkaline earth metal cations have a profound effect on the photophysics of the dir (Re) → π* (bpy) metal-to-ligand charge-transfer (MLCT) excited state in crown ether substituted complex 1. The unique cation-induced effects arise because of the influence of the "crowned" cation on the energy of the ligand-to-ligand charge-transfer (LLCT) excited state that is formed by charge transfer from the donor nitrogen to the electron-deficient metal center in the MLCT state (bpy)ReI-A → hv (bpy?-)MLCTReII-A →kic (bpy?-)LLCTReIA?+ (where bpy = 2,2′-bipyridine and A = the amine donor). In the absence of cations, the energy of the LLCT state lies below the MLCT state. As a result, kic is large and the LLCT state provides a path for rapid radiationless decay of the MLCT state. However, due to the ion-dipole interaction between the cation and the donor nitrogen in cation-crown complexes (1···Mn+), the energy of the LLCT state is higher than that of the MLCT state. Under these conditions, the MLCT state decays primarily by "normal" radiative and nonradiative decay paths. As a result, the MLCT emission yield is larger for the 1···Mn+ complexes compared to that for 1. Emission quantum yield and lifetime data for the 1···Mn+ complexes are interpreted by a kinetic model in which the rate-determining step for excited-state decay involves dissociation of the cation from the macrocycle. The crown-substituted complex 1 provides a paradigm for a MLCT-based cation sensor.
MacQueen, D. Brent,Schanze, Kirk S.
p. 6108 - 6110
(2007/10/02)

Non-acidic anti-inflammatory compounds: activity of N-(4,6-dimethyl-2-pyridinyl) benzamides and derivatives
The inhibition of the carragenin-induced rat-paw edema by previously synthesized N-(4,6-dimethyl)-2-pyridinyl) benzamides was evaluated.Amoung the 29 tested compounds, secondary benzamides 1, 12 and tertiary benzamide 60 exhibited a significant anti-inflammatory activity.It prompted us to envision a pharmacomodulation in this series by structural modifications on the homocycle, the amide function and the heterocycle.Although benzamide 38, acetamide 50 and benzylamine 56 elicited marked inhibitory activity, none was more active than N-(4,6-dimethyl-2-pyridinyl) benzamide 1. The mechanism of the anti-inflammatory action of 1 was investigated.The results showed that this molecule reduced eicosanoid biosynthesis but was unable to reduce cyclooxygenase or lipoxygenase activities.Although it did not directly block phospholipase activity, however, an inhibitory process at this level is likely.
Robert-Piessard, Sylvie,Le Baut, Guillaume,Courant, Jacqueline,Brion, Jean-Daniel,Sparfel, Louis,et al.
p. 9 - 19
(2007/10/02)