Top PDF Synthetic and structural studies of permethylscandocene and permethyltantalocene derivatives

Synthetic and structural studies of permethylscandocene and permethyltantalocene derivatives

Synthetic and structural studies of permethylscandocene and permethyltantalocene derivatives

of 0 to the metal center to give an 112 acyl complex.s This coordination mode activates the CO toward further reaction, as evidenced by observed dimerization and tetr[r]

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Synthetic and structural studies of 1 halo 8 (alkylchalcogeno)naphthalene derivatives

Synthetic and structural studies of 1 halo 8 (alkylchalcogeno)naphthalene derivatives

and torsion angles are listed in Table 1. Further crystallographic information can be found in Table 4 and the Supporting Information. The substitution of large halogen and chalcogen atoms in the 1,8-positions of derivatives 1-8 imposes a great amount of steric strain between the peri-atoms. The subsequent displacement of the peri-atoms within and away from the naphthalene plane is accompanied by a significant buckling of the naturally planar naphthalene skeleton and assists in alleviating the strain. The distortion observed correlates to the bulk of the two interacting atoms in the naphthalene molecule as indicated by the primary parameter for naphthalene distortion, the peri-distance. The structures of 1, 2, 4-8, reveal the halogen atom lies in close proximity to the E(alkyl) group in all cases, with non-bonded interatomic peri- distances (X···E) displaying a general increase when larger atoms occupy the close contact 1,8-positions (see Table 1, Figure 3). The X···E distances [3.06-3.34 Å] are less than the respective sum of van der Waals radii for the two interacting atoms [3.65-4.04 Å] [24] and in all derivatives this distance is between 82 and 88 % of the vdW sum (Table 1). [24] These short non-bonded peri-distances indicate the possible existence of weak intramolecular interactions. [25]
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Structural and synthetic studies of toxic terpenoids

Structural and synthetic studies of toxic terpenoids

Conversion of the ketone to cyclo- hexylmethylnitrile derivatives followed by oxidations of the allyl group and ring closure gave two series of decalin carbonitrile[r]

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Synthetic studies on R207910, aza-Diospongin A and hydroxylamine derivatives

Synthetic studies on R207910, aza-Diospongin A and hydroxylamine derivatives

VIII Chapter II: Asymmetric synthesis of aza (-)-Diospongin A as an iNOS inducer. Introduction: Nature has been the rich source of bioactive natural products and has laid basis for drug leads and new medicines since pre-historical era. Nearly half of the currently used drugs are of natural product origin derived either directly or designed based on pharmacophore. However the structural complexity, paucity, side effects of, these pharmacologically active natural compounds has set limitations to use them as drug candidates. Thus modification of bioactive natural products to structurally similar synthetic analogues with minimum molecular complexity while retaining pharmacological activity and reduced side effects has gained importance over time. In this context we chose to prepare aza-analogue of diospongin-A (1a).
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Synthetic, structural and spectroscopic studies of peri substituted systems and their complexes

Synthetic, structural and spectroscopic studies of peri substituted systems and their complexes

It was also noted, when the products were left overnight in chlorinated solvent, the solution changed colour from yellow to green. 31 P NMR of the green solution showed degradation of product, with the only peaks being those from the corresponding platinum chloro phosphine complex. Similar behaviour was also observed with the platinum complexes of naphthalene-1,8- dichalcogens and the oxidised derivatives of naphtho[1,8-cd]-1,2-dithiole. 11 The authors found that addition of small quantities of triethylamine to work-up and NMR solvents prevented decomposition; leading them to conclude that free hydrogen chloride in the solvent was causing decomposition. The same can be concluded in this instance.
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Structural and quantum chemical studies on aryl sulfonyl piperazine derivatives

Structural and quantum chemical studies on aryl sulfonyl piperazine derivatives

1. INTRODUCTION Sulfonamides, called sulfa drugs, a derivative or variation of sulfanilamide, act as antimicrobial agents by inhibiting bacterial growth and activity 1 . Also Sulfonamides were the first synthetic antibiotics to be used in clinic and they exhibit interesting pharmacological properties, such as selectivity to bacterial cells and low toxicity. Later on, a large number of sulfonamides derivatives were synthesized, characterized and tested for antibacterial 2 , antitumor 3 , anti-carbonic anhydrase 4,5 , diuretic 6,7 , hypoglycaemic 8 , antithyroid 9 or protease inhibitory activity 10,11 among others.
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Synthetic, structural, and spectroscopic studies of sterically crowded tin chalcogen acenaphthenes

Synthetic, structural, and spectroscopic studies of sterically crowded tin chalcogen acenaphthenes

As expected, the stronger 3c-4e Cl-Sn-E bonding present in 5-9 has a greater impact on counteracting the steric repulsion that invariably builds up between the closely aligned Sn and E lone- pair orbitals and is thus accompanied by a substantial reduction in molecular distortion. This is most apparent within the acenaph- thene plane where the divergence of the exocyclic Sn- C Acenap and E-C Acenap bonds is notably less pronounced [splay angles 5 10.9°[11.3°]; 6 12.6°; 7 10.8°; 8 12.7°; 9 9.8°] than in the tri- phenyltin derivatives 1-4 [splay angles 16-21°] (Figures 5 and 6).
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Synthetic, structural, and stability studies of metal complexes of cross -bridged tetraamine macrocycles

Synthetic, structural, and stability studies of metal complexes of cross -bridged tetraamine macrocycles

Ancillary ligands in this complex include one water as well as a bridging chloride from the ZnCfr2' counterion. The inter- and intra-molecular hydrogen bonding interactions from two such units result in a pseudo-dimeric structure (Figure 2.27). The distances of these hydrogen bonds range from 2.25 to 2.63 A while the Zn(l)-C l(l) bond is quite long at 2.629(2)A. The Zn(II)-OH 2 of 2.170 (5) A is within the average Zn - 0 bondlength o f 2.097 ± 0.049 A for a 6 -coordinate Zn(II) species .109 Only two previous reports were found in the Cambridge Crystallographic Database with this Zn(H 2 0 )(p- Cl-ZnCfr) structural motif. One contains triethanolamine and the other has pyridine-2- carbaldehyde as co-ligands .110’111 There are two reports o f 6 -coordinate Zn(II) complexes of cyclam and its derivatives with coordinated water.23ti)’23(1) However, the two ancillary ligands including H 2 O are found in the trans position. Since the significance of labile cis- coordination sites at Zn(II) centers for catalytic chemistry has often been invoked ,29^ ’112 the potential biomimetic reactivity at this type o f complex is clearly worthy of study.
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Synthetic, Spectroscopic, Structural and Computational Studies of Enyl and Ynyl Carbon-Rich Complexes

Synthetic, Spectroscopic, Structural and Computational Studies of Enyl and Ynyl Carbon-Rich Complexes

A simple protocol that allows the preparation of either “symmetric” A 3 or “asymmetric” AB 2 triethynyl methanol derivatives through the reaction of acetylide anions with chloroethylformate, has been explored. This synthetic protocol is not only high yielding, but avoids the harsh conditions used in literature methods. The molecular structures of Me 3 SiC≡C(COH)(C 6 H 4 I) 2 and HC≡C(COH)(C 6 H 4 I) 2 have been determined and analysed, with the packing motifs in the solid state arising from halogen interactions identified. The use of these ligands as branched core ligands has also been investigated, and whilst difficulties have been encountered synthetic work to resolve these has been initiated.
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Reactivity profile of a peri substitution stabilized phosphanylidene phosphorane : synthetic, structural, and computational studies

Reactivity profile of a peri substitution stabilized phosphanylidene phosphorane : synthetic, structural, and computational studies

18 the donor stabilization is rather efficient in these literature species as some of the derivatives were inert enough to be purified by column chromatography. An interesting observation from the reactions with chalcogens is that they proceed under relatively mild conditions, indicating that 1 is rather reactive in comparison to (for example) tertiary phosphines or cyclic oligophosphines. 24 In line with decreasing oxidizing power of elements on going down the Group 16, lower oxidation state phosphorus centers become more prevalent at the bottom of the group.
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Applications of X ray crystallography: studies into the structural perturbations of peri substituted naphthalene derivatives

Applications of X ray crystallography: studies into the structural perturbations of peri substituted naphthalene derivatives

Se Se Figure 4-1. Naphtho[1,8-c,d]-1,2-diselenole (Se 2 naph). Both of these procedures are in reality quite lengthy and present a number of synthetic hurdles. For example, the experimental details reported by Meinwald et al are sparse and contain essentially no directions on how to expose the reaction mixture to air, which usually results in low yields. Others have reported synthesizing dilithionaphthalene from 1,8-dibromonaphthalene. 3,4 This compound, like the 1,8-dichloronaphthalene used in Yui’s synthesis, is itself difficult to make and is usually obtained in low yield. 5 Another problem with Yui’s method is the use of Na 2 Se 2 , which is dangerous to synthesize due to the handling of elemental sodium and selenium, and ammonia gas. 2 For an inexperienced chemist, the
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STRUCTURAL STUDIES ON LAMELLARIN ALKALOIDS, TOTAL SYNTHESIS OF PURPURAMINE-K AND DEVELOPMENT OF NOVEL SYNTHETIC METHODOLOGIES.

STRUCTURAL STUDIES ON LAMELLARIN ALKALOIDS, TOTAL SYNTHESIS OF PURPURAMINE-K AND DEVELOPMENT OF NOVEL SYNTHETIC METHODOLOGIES.

The aza Diels-Alder reactions are becoming a mainstray for the synthesis of heterocycles and natural products, as they provide a rapid means of construction of functionalized heterocyclic rings with control of regio-, diasterio-, and enantio selectivity. Pyrano quinoline derivatives have been found to possess a wide spectrum of biological actions such as psychotropic, anti-allergic, anti-inflammatory and estrogenic activities.

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Synthesis, structural studies and antituberculosis evaluation of new hydrazone derivatives of quinoline and their Zn(II) complexes

Synthesis, structural studies and antituberculosis evaluation of new hydrazone derivatives of quinoline and their Zn(II) complexes

molecules with newer targets and with an alternative mecha- nism of action [1,2] . It is evident from the literature that quinoline-based hydrazone scaffolds are known to exhibit excellent anti-TB properties [3–8] . This broad spectrum of bio- logical and biochemical activities has been further aided by the synthetic flexibility of quinoline hydrazones, which allows the generation of a large number of structurally diverse derivatives and their metal complexes [9,10] . Further, various types of hydrazones have attracted continued interest in the medicinal field due to their broad-spectrum biological activities [11] . Among the ligand systems, quinoline hydrazone derivatives are highly important because, these ligands developed due to their diverse chelating ability, structural flexibility and phar- macological activities like antitumoural, antifungal, antibacte- rial, antituberculosis, antimalarial, and antiviral [12,13] .
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Studies of synthetic chalcone derivatives as potential inhibitors of secretory phospholipase A2, cyclooxygenases, lipoxygenase and pro-inflammatory cytokines

Studies of synthetic chalcone derivatives as potential inhibitors of secretory phospholipase A2, cyclooxygenases, lipoxygenase and pro-inflammatory cytokines

inhibition of TnF-α and il-6 release in lPs-stimulated macrophages LPS is a significant structural constituent of the outer membrane of gram-negative bacteria, and the literature suggests its role as an immunostimulator that induces systemic inflammation response, and particularly, the expression of pro-inflammatory cytokines, for instance TNF- α and IL-6. 52 In this study, chalcone derivatives were evaluated for their inhibitory activity against LPS-induced TNF- α and IL-6 release in mouse RAW264.7 macrophages. The macrophages were pre-treated with the tested compounds (at 10 m M concentration) for 2 hours and incubated afterwards with 0.5 m g/mL LPS for 22 hours. The levels of TNF- α and IL-6 in media were detected by ELISA and normalized by protein concentration of cells collected in homologous culture plates.
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Therapeutic journey of synthetic betacarboline derivatives:  A short review

Therapeutic journey of synthetic betacarboline derivatives: A short review

Quantitative structure–activity relationship (QSAR) studies have been performed on β- carboline derivatives to explore the structural necessities for antitumor activity. 3D QSAR studies were done using V-Life Sciences MDS 3.0 drug designing module to explain the structural requirements for the anti-tumor activity. The 3D- QSAR was performed using the Step Wise K Nearest Neighbour Molecular Field Analysis [(SW) kNN MFA] technique with the partial least-square (PLS) method on a database. Obtained best 3D- QSAR model having high predictive ability with q 2 = 0.743, r 2 = 0.721, pred_r 2 = 0.708 and standard error = 0.346, explaining the majority of the variance in the data with partial least square (PLS) components. The results of the present study may be useful on the designing of more potent compounds as antitumor drugs.
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Structural and synthetic studies of alkaloids of the Proteaceae

Structural and synthetic studies of alkaloids of the Proteaceae

The approach was based on hydrogen bonding studies and the correlation of observed v c_ o values for tropine and pseudotropine with values of known axial and equatorial hydroxy cycloa[r]

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Diverse derivatives of selenoureas : a synthetic and single crystal structural study

Diverse derivatives of selenoureas : a synthetic and single crystal structural study

A combination of strong intramolecular and intermolecular N–H ··· O hydrogen bonding, complemented by weaker interactions involving Se results in the supramolecular structure as shown in[r]

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“STUDIES ON NEW SYNTHETIC STRATEGIES FOR O- AND S-DERIVATIVES OF MONOTERPENES

“STUDIES ON NEW SYNTHETIC STRATEGIES FOR O- AND S-DERIVATIVES OF MONOTERPENES

Chapter 1 Oxygenated Monoterpene and Their Sulfur Analogs: Introduction A brief account of the natural occurrence of oxygenated and their sulfur analogs and their importance as aroma chemicals as well as synthetic approach to them are given, as an introduction to the present investigation. Functionalization of hydrocarbons is an important area in classical synthetic organic chemistry, and it continues to be a topic of active research even now. The present challenges are, the achievement of better regio- and stereoselectivities, clean reaction and facile workup of the product. In this context, there is growing interest in the use of electromagnetic radiation and ultrasound energy in chemical reactions. The potential of these techniques as synthetic tools is being vigorously explored by researchers world over.
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Synthetic and structural studies on dinuclear rhodium (ii) compounds

Synthetic and structural studies on dinuclear rhodium (ii) compounds

Structure Analysis And Refinement:- Direct methods (Rh atoms) followed by alternating cycles of least-squares refinement and difference-fourier synthesis. The asymmetric unit contains one badly disordered molecule of acetone in addition to the dication and two anions. Equivocal identification of the oxygen atom and the methyl groups proved impossible and these have been assigned arbitrarily. This has resulted in a few unsatisfactory thermal and structural parameters. However as the lattice solvent molecule makes no short contacts with the chemically important parts of the structure this imperfect solution has been accepted. Non-hydrogen atoms were refined anisotropically and hydrogens were placed in calculated
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NEUROPSYCHOPHARMACOLOGIC STUDIES OF MARIJUANA: SOME SYNTHETIC AND NATURAL THC DERIVATIVES IN ANIMALS AND MAN *

NEUROPSYCHOPHARMACOLOGIC STUDIES OF MARIJUANA: SOME SYNTHETIC AND NATURAL THC DERIVATIVES IN ANIMALS AND MAN *

Many investigators have observed that marijuana smoking or T H C derivatives in man cause a significant increase in heart rate.5751 Manno and coworkersm and Renault[r]

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