Sull'acido salicilico

Couper, Michael R.

doi:10.1007/bf02735629

Cited by 5 publications

(6 citation statements)

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“…Despite the failings of its underlying theory, the spirit of this work was carried through in the writings of Berzelius, who replaced Dalton's cumbersome patterned circles with the now familiar (and then easily printed) alphabetical abbreviations. [4,5] Couper, Crum Brown, and Kekul e further advanced the notion of chemical structure via Frankland's concept of valence, [6] Couper being the first to depict a bond between a pair of carbon atoms with a line [7] (see Fig. 1b) and the latter famously deciphering the structure of the benzene molecule [8] (Fig.…”

Section: Introductionmentioning

confidence: 99%

Rhorix: An interface between quantum chemical topology and the 3D graphics program blender

et al. 2017

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Chemical research is assisted by the creation of visual representations that map concepts (such as atoms and bonds) to 3D objects. These concepts are rooted in chemical theory that predates routine solution of the Schrödinger equation for systems of interesting size. The method of Quantum Chemical Topology (QCT) provides an alternative, parameter‐free means to understand chemical phenomena directly from quantum mechanical principles. Representation of the topological elements of QCT has lagged behind the best tools available. Here, we describe a general abstraction (and corresponding file format) that permits the definition of mappings between topological objects and their 3D representations. Possible mappings are discussed and a canonical example is suggested, which has been implemented as a Python “Add‐On” named Rhorix for the state‐of‐the‐art 3D modeling program Blender. This allows chemists to use modern drawing tools and artists to access QCT data in a familiar context. A number of examples are discussed. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

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Section: Introductionmentioning

confidence: 99%

Rhorix: An interface between quantum chemical topology and the 3D graphics program blender

et al. 2017

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“…Based on the pioneering proline-catalyzed enantioselective aldol reaction, first developed in the early 1970s independently by the Weichert 9 and Hajos 10 research groups, the first asymmetric domino Robinson annulation was proposed by Bui and Barbas only in 2000. 11 Among a large series of pyrrolidine-like amino catalysts, L-proline (1) gave the best result when methyl vinyl ketone reacted with 2-methylcyclohexa-1,3-dione leading to the expected Wieland-Miescher ketone (2) in 49% yield and 76% ee (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Organocatalyzed Domino Synthesis of Six-Membered Carbocycles

et al. 2013

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Abstract:Polysubstituted chiral cyclohexanes and cyclohexenes are important building blocks in organic synthesis. From historical and pioneer reports to the most recent accounts, this review focuses on domino enantioselective organocatalytic methodologies that have allowed the control of the relative and absolute configurations of up to six stereogenic centers in the construction of these versatile molecular architectures.

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“…Electrophilic aromatic bromination was probably one of the earliest reaction to be discovered and studied by organic chemists. 1 Its mechanism is generally regarded as starting from a p-complex B, 2 a pre-reactive intermediate that evolves into a s-complex C (the Wheland intermediate), the formation of which represents the rate-determining step of the process in most cases (Scheme 1). 3 N-Bromosuccinimide is a well-known reagent for electrophilic aromatic bromination.…”

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Electrophilic Bromination of meta-Substituted Anilines with N-Bromosuccinimide: Regioselectivity and Solvent Effect

Bartoli¹,

Cipollone²,

Squarcia³

et al. 2009

Synthesis

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N-Bromosuccinimide-mediated electrophilic aromatic bromination of a series of anilines substituted with an electron-withdrawing group in the meta position was investigated. The regioselectivity of the reaction is markedly dependent on the polarity of the solvent and the bromination reaction can be tuned by appropriate selection of the reaction medium.Brominated aromatic compounds are of considerable interest, both for their intrinsic properties (numerous biologically active molecules contain a brominated aromatic unit) and for their use as reactive intermediates in the synthesis of important drugs, because of their ability to undergo carbon-carbon and carbon-heteroatom bondformation reactions.Electrophilic aromatic bromination was probably one of the earliest reaction to be discovered and studied by organic chemists. 1 Its mechanism is generally regarded as starting from a p-complex B, 2 a pre-reactive intermediate that evolves into a s-complex C (the Wheland intermediate), the formation of which represents the rate-determining step of the process in most cases (Scheme 1). 3 N-Bromosuccinimide is a well-known reagent for electrophilic aromatic bromination. In 1979, Mitchell et al. 4 reported that N-bromosuccinimide in N,N-dimethylformamide is a mild and selective reagent for nuclear monobromination of reactive aromatic compounds. Since then, several regioselective methods have been developed that use N-bromosuccinimide alone 5 or in combination with a variety of additives, both for deactivated 6 and activated 7 ortho-and para-disubstituted substrates. Surprisingly neither the regioselectivity nor the solvent effect in the bromination of meta-substituted aromatics with Nbromosuccinimide has been extensively investigated. meta-Substituted anilines 1a-h (Scheme 2), all of which contain an electron-withdrawing group, seemed to be appropriate starting points for our study, the aim of which was to explain some unexpected results obtained in our laboratories during routine synthetic work on analogous substrates. Bromination of 1a-h by N-bromosuccinimide was studied in a panel of seven solvents. Scheme 2 X = (a) NO 2 ; (b) CF 3 ; (c) CN; (d) CO 2 Me; (e) COMe; (f) F; (g) Cl; (h) Br The polarity of the solvents examined ranged from low in the case of dioxane [dielectric constant (e) = 2.2] to high in the case of dimethyl sulfoxide (DMSO; e = 47.2). The results obtained (Table 1) confirm that the regioselectivity of the reaction is markedly dependent on the solvent.Plots of the molar fraction of isomers 3a, 3d, 3e, and 3f against e (Figure 1a; curves for 3c, 3d, 3g, and 3h are not reported for the sake of clarity) show an almost linear correlation until e reaches a value of around 20, where the curves reach a plateau. A similar trend is observed with solvent mixtures of tetrahydrofuran (e = 7.5) with increasing fractions of water (e = 80) (Figure 1b; curve for 3b). Regardless of the nature of X, bromination seems to be very selective in polar media (DMF, DMSO), where 3 is formed almost exclusively.

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Sull'acido salicilico

Cited by 5 publications

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Rhorix: An interface between quantum chemical topology and the 3D graphics program blender

Rhorix: An interface between quantum chemical topology and the 3D graphics program blender

Enantioselective Organocatalyzed Domino Synthesis of Six-Membered Carbocycles

Electrophilic Bromination of meta-Substituted Anilines with N-Bromosuccinimide: Regioselectivity and Solvent Effect

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Sull'acido salicilico

Cited by 5 publications

References 0 publications

Rhorix: An interface between quantum chemical topology and the 3D graphics program blender

Rhorix: An interface between quantum chemical topology and the 3D graphics program blender

Enantioselective Organocatalyzed Domino Synthesis of Six-Membered Carbocycles

Electrophilic Bromination of meta-Substituted Anilines with N-Bromosuccin­imide: Regioselectivity and Solvent Effect

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Electrophilic Bromination of meta-Substituted Anilines with N-Bromosuccinimide: Regioselectivity and Solvent Effect